IfAj*
ee
RdKn
CTRONIC PERCUSSION
EFFECTS
»
9« w
Qhtr
HIS ISSUE
FOR SMALL CRA
{flcgd Trade Mark}
SOLDERING EQUIPMENT
for ike
DISCRIMINATING
ENTHUSIAST
ILLUSTRATED:
L64 -k" BIT INSTRUMENT IN
L700 PROTECTIVE SHIELD
APPLY DIRECT TO:
SALES & SERVICE DEPT.
ADCOLA PRODUCTS LTD.
ADCOLA HOUSE
GAUDEN ROAD
LONDON, S.W.4
TELEPHONE 01-622 0291
ABOUT BOOKS BY 0. A. BRIGGS IN
HIGH FIDELITY MAGAZINE
U.S.A. JANUARY 1968
Is there any reason why audio books can't be written in high style?
G. A. Briggs has been doing it ever since High Fidelity first emerged
from the exclusive domain of engineers and began to be cultivated
by the cultivated. Consider his temerity in opening a chapter on
distortion in his classic Sound Reproduction with a quotation from
Milton: ". . . dire was the noise of conflict". Or recall his wit in
replying to a letter from a man who asked why "the body missing"
from the sound when he put a back on his home-made speaker
enclosure, and why the speaker sounded better when he took the
back off again. Briggs wrote ". . . when you leave off the back . . .
you obtain . . . reflection from the wall . . , use the system which
sounds best, even if contrary to every textbook. In any case, as the
body has disappeared, there would not be much point in screwing
[down the lid of the coffin,"
Nojjpdy else writes them with quite that flair.
The BRIGGS books listed below are still
obtainable.
AERIAL HANDBOOK (second edition)
176 pages, 144 illustrations
Price (semi -stiff cover) 15/- (16/- post free) \%X
(cloth bound) 22/6 (24/- post free)
CABINET HANDBOOK
I 12 pages, 90 illustrations
Price 7/6 (8/6 post free)
AUDIO BIOGRAPHIES
344 pages, 64 contributions from pioneers
and leaders in Audio. Cloth bound
Price 25/- (26/6 post free)
MUSICAL INSTRUMENTS AND
AUDIO
240 pages, 212 illustrations. Cloth bound
Price 32/6 (34/- post free)
LOUDSPEAKERS
Fifth edition — 336 pages, 230 illustrations.
Cloth bound
Price 25/- (26/6 post free)
A TO Z IN AUDIO
224 pages, 160 illustrations. Cloth bound
Price 15/6 (17/- post free)
MORE ABOUT LOUDSPEAKERS
136 pages, 1 12 illustrations
Price 8/6 (9/6 post free)
PIANOS, PIANISTS AND SONICS
190 pages, 102 illustrations. Cloth bound
Price 18/6 (20/- post free)
#
AUDIO AND ACOUSTICS
168 pages, 140 illustrations
Price 12/6 (13/6 post free)
ABOUT YOUR HEARING
132 pages, 1 12 illustrations
Price (semi-stiff cover) 15/6 (16/6 post free)
Cloth bound 22/6 (24/- post free)
Sold by Radio Dealers and Book Shops or in cose of difficulty direct
from the Publishers
RANK WHARFEDALE LTD.
IDLE, BRADFORD, YORKS. Tel.: Bradford 6I25S2
Build Your Own Heathkit Electronics
A kit for every interest — Home Workshop — Hi-Fi — Radio — Test — Amateur
Latest STEREO TAPE RECORDER, STR-1
Fully portable — own speakers
Kit £45. IB.
FOR THIS SPECIFICATION
i track stereo or mono record and
playback at 7±,3f and Hips. Sound-
on-soiind and sound-with-sound
capabilities. Stereo record, stereo
playback, mono record and playback
on either channel, 18 transistor circuit for cool, instant and depend-
able operation. Moving coil record level indicator, Digital counter
with thumb-wheel zero reset. Stereo microphone and auxiliary inputs
and controls, speaker/headphone and external amplifier outputs . . .
front panel mounted for easy access. Push-button controls for
operational modes. Built-in stereo power amplifier giving 4 W rms per
channel. Two high efficiency 8" n 5" speakers. Operates on 230V
a.c. supply.
Versatile recording facilities. So easy to build — so easy to use.
Latest STEREO AMPLIFIER, TSA-12
12 x 12 watts output
Kit £30. 10.0 less cabin*
Cabinet £2. 5, extra
FOR THIS SPECIFICATION
17 transistors, 6 diode circuit. -JildB, 16 to 50,000c/s at 12W
per channel into 8 ohms. Output suitable for 8 or 15 ohm
loudspeakers. 3 stereo inputs for Gram, Radio and Aux.
Modern low silhouette styling- Attractive aluminium, golden
anodtsed front panel. Handsome assembled and finished
walnut veneered cabinet available. Matches Heathkit models
TFM-1 and AFM-2 transistor tuners.
Full range power . . . over extremely wide frequency range.
Special transformerless output circuitry. Adequately heat-
sinked power transistors for cool operation — long life, 6 position
source switch.
High-performance CAR RADIO, CR-1
Superb long and medium wave
entertainment wherever you drive.
Complete your motoring pleasure
with this compact outstanding unit.
8 Latest semiconductors (6 transistors, 2 diodes). For 12V positive or 12V
negative earth systems. Powerful output (4W). Praassembled and aligned
tuning unit. Push-button tone and wave change controls. Positive manual
tuning. Easy circuit board assembly. Instant operation, no warm-up time.
Tastefully styled to harmonise with any car colour scheme. High quality
output stage will operate two loudspeakers if desired. Can be built for a
total price.
KIT (less speaker) £12. 17. Oincl. P.T.
6" x 4" Loudspeaker £1. 4. 5 extra.
Latest Portable Stereo Record Player, SRP-1
Automatic playing of 16, 33, 45
and 78 rpm records. All transis-
tor — cool instant operation. Dual
LP/78 stylus. Plays mono or
stereo records. Suitcase port-
ability. Detachable speaker en-
closure for best stereo effect.
Two Sin x Sin special loud-
speakers. For 22Q-250V a.c.
mains operation. Overall cabi-
net size 15* x 31 : 10±in.
Compact, economical stereo and mono record playing for the whole
Family — plays anything from the Beatles to Bartok. All solid-state
circuitry gives room filling volume.
KIT £27.15.0 incl. P.T.
SSU-1
A wide range of
SPEAKER SYSTEMS
HI-FI SPEAKER SYSTEM. Model
SSU-1. Ducted-port bass reflex cabi-
net "in the white". Two speakers.
Vertical horizontal models with legs, Kit
£12. 12. without legs, Kit £11. 17. 6 incl.
P.T.
The BERKELEY SUM-LINE
SPEAKER SYSTEM, fully finished
walnut veneered cabinet for faster con-
struction. Special 12* bass unit and 4"
frequency unit, Range 30-
Size 26" x 17" only 7j" deep.
attractive styling. Excellent
mid/high
17,000c/s,
Modern
value.
Kit £19. 10. 0.
Berkeley
SEE HEATHKIT MODELS AT:
GLOUCESTER
Factory and Showroom, Bristol Road,
LONDON
233 Tottenham Court Road, W.1.
BIRMINGHAM
17-18 St. Martin's House, Bull Ring.
Demonstrations by arrangement.
Deferred terms available over £10 (U.K. only).
Prices quoted are Mail Order prices.
Send
for
Latest
FREE
Catalogue
36 pages,
many
models
in Colour
Transistor Portables
UXR-1, now available in Modern
coloured cases or leather.
6 transistor, 1 diode circuit. 7 x 4in.
speaker. LW and MW coverage.
Case: brown leather, or colours
navy blue, coral pink, lime green.
Please state 2nd choice.
Kit £11. 19. 0, Colour
Kit £12. 18. 0. Leather
UXR-2, choice of black or brown
real leather cases.
7 transistor, 3 diode circuit. Battery
saving circuitry. LW and MW
coverage. Pushbutton wave change.
Slide rule tuning.
Kit £14. 18. 0. leather 'UXR^^*"""MIBi^
j HEATHKIT
P lease add rest all enquiries to
I DAYSTROM LTD., Dept. P.E5, GLOUCESTER
' rn Please send me FREE CATALOGUE
j I Full details of mod el (s)
' NAME - -
|
1 ADDRESS -
.L__
313
GOODMANS
t_j*»U3Beyt¥_
HIGH FIDELITY
MANUAL
A Guide to full
listening enjoyment
The Manual is much more than a cata-
logue ol Goodmans High Fidelity Loud-
speakers—it contains informative articles,
including advice on stereo, special begin-
ners page, aid full cabinet drawings.
You'll find it interesting as well as
informative.
The Perfect Combination
MAXAMP30
TRANSISTORISED STEREOPHONIC HIGH FIDELITY AMP-
LIFIER 15 + 15 watts ■ Silicon solid state ■ Integrated pre-ampltfier
Negligible distortion • £49,10.0.
STEREOMAX
MATCHING AM/FM STEREOPHONIC FM TUNER
Transistorised • Outstanding specification - Stereo de-coder (optional)
£60.0.0. + £11.18.3. P.T. inc. Surcharge.
Both MAX AMP 30 and STEREOMAX have polished wood cases
flOi" x 5%" x ?i" deep) in Teak or Walnut to order
Full specifications of the Maxamp 30 and Stereomax are given in
the High Fidelity Manual — send the coupon for your FREE copy —
or pay an early visit to your Goodmans dealer.
r-z^z
Please send Hi-Fi Manual together with name and address
ol my nearest Goodmans dealer.
P.E.3
GOODMANS LOUDSPEAKERS LTD
AXIOM WORKS • WEMBLEY • MIDDLESEX. Tel: 01-902 1200
AUDIO
TRANSDUCER
A new concept
in sound
reproduction
The '309' Audio Transducer repre-
sents a breakthrough in sound repro-
duction without the use of hard to
place loudspeakers. It has been
designed to reproduce sound by
utilising the vibrant qualities of
wooden, plastic, glass, metal and
similar surfaces. It has an exception-
ally good frequency response and
provides excellent quality music and
speech, A versatile unit, fully water-
proof and suitable for many indoor
and outdoor uses. Impedance 8-15
ohms. Power Handling 10 watts.
TGNS. P, & P. 4/6
Complete with simple instructions
Available from most dealers or direct from the Sole U.K. Distributors
ELECTRO-APPARATUS (LONDON) LTD.
BENTFIELD END, STANSTED, ESSEX Tel: Stansted 3437
MARTIN IS HIGH-FIDELITY
■«. PREFERRED FOR RELIABILITY,
QUALITY, ADD-ON-ABILITY AND
ECONOMY
You can do so much with MARTIN
kits. The system, of using pro-fabri-
cated transistorised, units which can
be interlinked in a variety of ways
enables you to assemble the com-
bination of your choice and then
extend it unit by unit until you
possess a full stereo gramophone
and radio assembly. When new units
are produced, they can be added to
existing equipment very easily with
the advantage that you can continue
to use equipment you already have,
so that your installation is always
up to date. Most important of ail
is the power and quality which
MARTIN Audiokits give you. Their
sturdy construction assures com-
pactness without sacrifice to quality
or efficiency. They offer excellent
value, are very easily installed and
will give years of unfailing service.
That is why people prefer MARTIN
— it's simple to instal, good to
listen to, and looks completely
professional.
STEREO CONTROL
ASSEMBLY
ONLy FROM MARTIN
MARTIN AUDIOKITS are available for
Mono, and can be doubled up for
stereo, or as complete stereo units. 3
ohm and 15 ohm systems are available.
There is a special pre-amp for low out-
put pick-ups and escutcheon panels to
suit the arrangement you choose. The
tuner is styled to match.
Start by sending for leaflets at once
AMPLIFIER SYSTEMS • TUNERS • RECORDERS
UNITS INCLUDE:
■ 5-stage input selector
■ Pre-amp tone controls
■ 10 watt amp. (3 ohms)
■ 10 watt amp. (15 ohms)
■ Mains power supply
I F.M. Tuner
Trade enquiries invited
MARTIN ELECTRONICS LTD. ^LtSSST^SSSfWi
MARTIN ELECTRONICS
154 High Street, Brentford, Middlesex
Please send RecordakitF.M. TunerlAudiokit
Hi-Fi Leaflets. (Strike out items not wanted)
Name ....
Address
■••■■■•■•■■■■■■•■•■■■••(■•••••■••>
P.E.S/68 ■
••■■■■ ■■■•■«•*■■!
314
BUILD YOURSELF A QUALITY TRANSISTOR
RADIO— FULL AFTER SALES SERVICE!
THE MAGNIFICENT
ROAMER
SEVEN WAVEBAND PORTABLE AND CAR
RADIO WITH A SUPER SPECIFICATION
• 7 FULLY TUNABLE WAVE BANDS— MW1, MW2, LW, SW1,
SW2, SW3 and Trawler Band.
• Extra Medium waveband pro-
vides easier tuning of Radio
Luxembourg, etc.
• Built in ferrite rod aerial for
Medium and Long Waves.
• 5 Section 22 in. chrome plated
telescopic aerial for Short Waves
— can be angled and rotated for
peak S.W. listening.
• Socket for Car Aerial.
• Powerful push-pull output.
7 transistors and two diodes
including Philco Micro-Alloy
R.F. Transistors.
make 7 x4 in. P.M.
• Famous
speaker.
• Air spaced ganged tuning con-
denser.
• Separate on/off switch, volume
control, wave change switches
and tuning control.
• Attractive case with hand and
shoulder straps. Size 9 x7 x4 in.
approx.
• First grade components.
• Easy to follow instructions and
diagrams make the Roamer- 7 a
pleasure to build with guaran-
teed results.
Total building costs
£5.19.6 p * p
Parts price list
easy build plans 3/
(FREE with parts)
Total building costs
42/6 %%"•
Attractive «iso with red speaker grille. SlzaSj :,
il x llin. J'uliy tunable. 7 staj;K»— 8 transistors
atid 2 dioiles— fflrrite rod aerinl. tuning condenser,
volume control, fine tone roper dynamit: Sin.
speaker, all Ural grade components. Easy build
plans anil parts price list 1/6 (FBEE with parts).
Total building costs
39/6 \% p -
MEDIUM WAVE, LONG WAVE
AND TRAWLER BAND PORTABLE
Attractive black and gold ease. Size fi} x 1| x
Hi in. Fully tunable over both Medium and Lour
Waves with extended M.W. baud for easier tuning
nf Luxembourg 1 , etc, .Ml first grade components,
7 stages — & transistors and 2 diodes— super-
sensitive ferrite rod aerial, fine tone 3tn. moving
coil speaker, etc. Easy build plans and parte
price List, 3/5 (FREE with parts).
NEW MELODY MAKER SIX
3 WAVEBAND PORTABLE
8 stages — 6 transistors and 2 diodes
Covers Medium and Long Waves and EXTRA M.W. BAND FOR EASIER TUNING OF
LUXEMBOURG, ete. Top quality 3 in. Loudspeaker Tor quality output. Two RF
stages for extra boost. High "Q" 6in, Ferrite Rod Aerial. Approx. 350 milliwatts push-pull out-
put. Handsome pocket size case with gilt fittings. Size 6i :•; 3 J ;< liin.
This amazing receiver
may be built for only
69/6
P. &.P. 3,6
Parts Price List and easy build plans 2f m
(Free with parts}.
Total building costs
79/6 -■£-■
Attractive ease with gilt fittings. Size 7= K oi >:
I Jin. World wide reception. Tunable on Medium
and Long Waves, twn Short Waves. Trawler
Baud plus an extra M.W. band for cagier tuning
of Luxembourg* etc. .Sensitive ferrite rod aenal
and tek'H'ftplc aerial for S3WN*t WiwCS, AM
lop grade c<niii]K>iicuis» 8 StUfW- «J trwwtetott
and 2 diodes int-Sin Eiili^ Philoct Mhin-Alfoy K.F.
TranatatorS, etc (carry ins strop I/O evtr:i). Ensy
build plana ami porta price Ret 8/- (PttBE with
parts) .
Total building costs
69/6 p & p
THREE WAVEBAND PORTABLE
WITH 3in. SPEAKER
Attractive ease size 7 £ ■< 5 \ N IJin, with gilt
fittings. The ideal radio for home, car or outdoors.
Covers Medium and Long Waves and Trawler
Ha mi. Special circuit incorporating '2 K,F. stages,
puBh-pull output, ferrite rod aerial, 7 transistors
and 4 2 dlodi-i» liin. apeaker (will drive larger
speaker) anil nil first grade components. Price
list 2h (FKEE with parts).
RADIO EXCHANGE Ltd
Callers side entrance Barratt's Shoe Shop. Open 9-5 p.m. Saturday 9-12.10 p.m.
61a HIGH STREET, BEDFORD
Telephone: Bedfo rd 52367
315
LINO-AIR
(MINUSX)
ALPHABETICALLY...
we can list the names
GEOGRAPHICALLY...
we can list the countries
All over the world students know that
CREI HOME STUDY COURSES are sup-
plying the answer to their need for
advanced Technical Education in the field
of Electronic Engineering Technology.
CREI PROGRAMMES ARE AVAILABLE IN:
Electronic Engineering Technology
Industrial Electronics for Automation
Computer Systems Technology
Nuclear Engineering
Mathematics for Electronic Engineers
Television Engineering
Radar & Servo Engineering
Citv & Guilds of London Institute :
Subject 49 and Advanced Studies
Subject No. 300
Write for free brochures to:
C.R.E.I. (London) (Dept. P.E.8 )
WALPOLE HOUSE,173/176SLOANEST. T LONDON S.W.1
Telephone : Belgravia 8662
INTERNATIONAL DIVISION OF CAPITOL RADIO ENGINEERING INSTITUTE WASHINGTON D.C
i ' — " - " — —[
PFease send me (for my information and entirely without obligation) full details j
of the educational programmes offered by your institute [_
Send details of the City 6* Guilds Programme \~_
I
Name I
Address
Electronics Experience
- I
I
C.R.E.I. { LONDON) (DEPT. P.E.8), WALPOtE HOUSE, 173-176 SLMKE STREET, S.W.1 I
COMM
SiflWW^
WE HAVE A COMPLETE RAHOE 0T KEW
AltD OLD TTPKS OF VALVSS. TRANSIS-
T0B8 AJTD DIODES, FULL LISTS AVAIL-
ABLE OH AFEL1CATI0K.
V60201P 8/-
V6030 10/-
BFYOO 8/8
BFY61 7/-
BFY62 6/-
BYZ12 10/-
BYZ13 10/-
BCY33 7 6
BCY34 8/6
BCY10 7/8
BCY38 9/6
BCY39 12/6
BCY12 7/6
AC107 14/6
AC127 »/-
ACY17 8/8
ACY1D 6/6
AOY20 s/s
ACY21 e/-
ACY22 4/6
AF102 18/-
AF114 71-
AF11S 6/6
AF110 7/-
AF117 6/-
AF118 17/6
AF124 10/-
AF125 10/-
AF126 10/-
AF127 fl/6
AF139 10/-
AFimj its
AFZ11 17/-
AFZ12 12 6
A8Y20 8/8
HAT 100 7/8
HAT101 S/6
MAT1BO 7/9
MAT! 21 8'S
P.P. and insurance 2;-
EZ80
6/6
EZ81
8/8
PCC84
8/6
PCL8B
11/8
PCL82 10/B
PCL88U/6
KT66
w/e
KT88
W/6
DY8S
9/6
EBC33
96
DK96
fl'S
DAF96 7/9
DL9S
86
DF96
>/-
PY81
7/6
FL81
8/6
PY83
10/B
PL36
16/8
OAB
4/6
OA3
87-
OA71
3/6
OA81
m
OA96
1,'tl
OA200
3/3
OA202
4/3
GA203
*l-
OA12C
7 8
OA9
4/8
OAJO
3/-
OA47
»i-
OA70
2/-
OA7U
2/6
IN91
>/-
IN253
71-
1N234
4f-
IN255
6/8
INB37
6/6
IN 647
W-
1N237
6/6
IN2374 16/-
IN2379 26/-
1X38
3/6
INTJ5S
3/6
GEX44 8/8
CEX5
1 it/-
FGT Power
Mount
i/9
Klta
OTOR
Made by CJrouiptun Parkinson- Single phase
i h.p. Motor. 230/25OV; &0 cycles, I-3A,
1,424 r.p.m. Continuous rating. rtpiudle
l|in. x Sin. ilin. Overall size leas spindle
approx. 8 :■: Oin. Perfect condition. A
bargain lor the workbench. ONLY 79/6,
Carriage 20/- li h,p. Motor also available
B9/8, Carriage 20/-).
SELECTOR DRIVE
Numerous
applies*
tlOQB.
Electro
I'laguet
and brass
tooth
wheel.* A
switch
wafer and
contacts
ace
coupled
* ^^ totals
iiud arranged to be on lor 10 pulses and off
for IS. An Auxiliary contact is normally
on but ofl 1 in every 26. Complete with
suppressor, resistors, plus series contact
for continuous operation. Ideal window
displays, twitching lamps, models, etc.
12V or 24V d.c. Brand new and boxed
18/8. P. & P. 2/ti.
SYNCHRONOUS CLOCK
MOTORS
Geared for 40
revolutions per
hour. 230V W
cycle. With
mounting
flanges. 3 lie
appro*. 11 in.
deep -■- 21 m.
dia. ONLY
22/6. P. & P.
2/6.
DELAY ACTION TIME
SWITCH
Ideal for model
makers, record
players, tape
decks, etc.
8.3 d,c. Motor.
10,900 r.pjn, at
230mA, ljln X
lin dia. Shalt illl
long x 3J84in dia.
6/6. P. & P. 2/6.
9V d.c. Grim deck
replacement motor.
2in X. liin dia.
Shalt lin Jong x
3/32in. 17/6. T. * P-
Made by
Smithi. A.i_,
operation 200/
250V. Double
pole, will give
time delays
from 0-10
minutes. Size
2iln. dia. x
2 flu. long inc.
Jin. x 3/1 6 in
dia. spindle.
BARGAIN riUCE 17/6. P. * P. 2/«.
UNREPEATABLE BARGAIN?
FANE 122/17
12in 2a WATT
HEAVY DUTY
HI - FI
LOUD
SPEAK-
ERS.
With high
efficiency
Anti-
strop Ic
Kerrite magnet. 17.000 gauss. Imp.
3-5 ohms. Brand new and guaranteed.
List Price £12.' USD AIK TRICE
18.19.8. P. * P. 7/6,
E.KJ. COMBWATIOTf
LOUD SFEAKBRS
13} x 8 lin. Elliptical
with 3 lin dia. Tweeter.
Imp. 8 ohms. Power
handling 10 watte. Brand
new and guaranteed. List
price £8,6.0. LIND
AIR PRICE 99/6, P. &
P. 7/6. {AIM available
without tweeter 60/6
P. A P. 7/61.
b'anc 302 3in TWEETERS.
Imp. 3-5 ohms. 17,000
gauss. 12 watt. Brand
New and guaranteed. List
Price £3.15.0. LIND-AIR
PRICE 58/6, P. A P. 3/8.
$€£ LIND-AIR 0PP0$/rZ
LINO-AIR
(OPTRONICS) LTD.
25 & 53 TOTTENHAM COURT ROAD, LONDON, W.1. ret. 01.590 4534,7679
Open 9-6 p.m. Monday to Saturday inclusive. Open Thursday until 7 p.m.
ALL POST
ORDERS TO
Dept. P.E. 568
25 Tottenham
Court Road
London, W.1
1-3 WATT AMPLIFIER
An Ideal baits foe building your own port-
able record player. Just add speaker and
turntable, and you will have an above*
average mode) far a. mere fraction of the
cost. 2-3 -watt printed circuit wltb
control panel on flying toad. OK/ OFF,
TONE CONTROL AND VOLUME,
colourful escutcheon. Brimar valves:
EZ80, ECL82 and composite Installation
booklet. Price £4 C ft ft * P- 3/6.
MAGNAVOX-COLLARO 14] TAPE
DECK!
The very latest 3-speed model— 1|, 3j, 7i i.p.B.
available with either 2 track or 4 track head.
Features Include: Pause control; digital counter;
fast forward and rewind; new 4-pole, fully
screened induction motor; Interlocking keya. Size
of top plate 131 x 11 x Biio deep below unit
plate. For 200/260V a.c. mains, DO c/s operation.
New, unused and fully guaranteed.
VSt £10.10.0 *g? £13,19.6
Carriage and Packing 12/(5 extra.
FOB USE WITH ABOVE DECKS
2 track model 114.18 6; 1 track model 116.19.8. Carriage and Packing 12/3 .
MULTIMiTEHJ
9 in 1 ELECTRONIC KIT
MODEL TTC.10O1.
20.000 O.P.V. with
overload protection;
d.C. volts, S, 29. 12fi,
000, 3,500V; a.c.
volts, 10. 50
100 V; d.c.
260mA to
With prods
Carry hist case
ONLY 85J-.
P. ft F. 3/fl.
250,
mA
50A.
and
MODEL TTC.
1030. 50,000
OJ.V.; d.C
vol l =. 0-3, 12,
SO, 120, 300,
800, 1,200 V;
a.c. volte, 6, 30.
130. 000,
1,200V; d.o.
mA 0-03-300.
with prod*
and carrying
case ONLY
(11.19.0, P. A
P. B/-.
Build nine different projects from one
basic kit — simple Instructions, do tech-
nical knowledge required for you to build
a Police Siren, Metronome, Morse Code
amplifier, Electronic Massager, W/T
Transmitter, Radio, Telephone, One-
translator Radio Two-transistor Radio,
Electronic Music Kit. Completely safe-
operated on 9V PF3 battery. Hours of
fun for boys and dads of all ages. Complete
with all parts and simple step by step
instructions. ONLY 69/8. P. & P. 5/-.
■'■" li ll'll l tiHiH-1
Input 0-200, 220,
240V
Output 110 V
50W 11.7. 8
1.000W (8.8.0
75W (1,17.0
l.oOOW (15,15.0
100W £2.5.0
2.000W 118.10.0
160W (8.16.0
3.000W (25, 10.0
2001V fS.5.0
4.000W (34.18.0
3O0W 84.8.0
0-S0V, 1A 80/-
400W (4.19.8
0-80V. }A 17/8
500W (5.0.8
0-SOV, 2A 87/6
600W 88.8,8
0-30V, 3A 4*/-
Fost extra.
Input 2QO-25QV 60c/a.
24V 3AU.U.8 24V 8 A (6.5.
24V A (3,15.0 24V 12A (4,15,0
Post extra.
Mains and Output Transformer lists avail-
able on request.
GOODMANS SPEAKER BARGAINS!
Sin 3 ohms, 18/8; Bin. 3 ohm, £9/6.' Sin.
3 ohm, S2/B; 10ln 5 ohm, 88/-; 10 x Gin.
3 ohm, 38/8; Tweeter, 18/8. P. & P. 3/0
per Speaker.
9€£0PP0SIT€
Vantemv Table Top V Aerial BBC/IT V,
26/8.
Crest* Room Aerial Band I.'ll/Ill. Cream
or Black, 88/§.
Yeemstler Table Top VHF/UHF Tunable
Aerial. Chrome or Orey, 76/6.
YAM all Channel Table Top Aerial BBC1,,'
2/ITV/VHF. 66/-.
HL623 Loft Aerial HILO V + 5 tor vertical
Band I/UJ. With mounting ami and
bracket, 58/-,
Hew Major 10 element BBC2 Aerial for loft
or outdoor fixing. With roller bracket for
up to 2in dia. mast, 45,18.
HI, Hunter 13 element BBC2 Aerial as
above, 67/-.
El, Explorer IS element BBC2 Aerial as
above, 68/-,
Lolt Six. 6 element BBC2 Aerial for loft or
outdoor fixing. With arm and bracket,
87/6.
J-Beam 4 element outdoor Baud 11
VHF/FM Stereo Aerial. With mast, 87'-.
Please add 4/- postage.
STEREO HEADPHONES
STEREO HEADPHONES
Enjoy Stereo Bound
as you have never
heard It before.
MODEL TTC.
ami as illustrated
soft padded ear-
phones. Adjustable
headband. Impe-
dance 8 ohms per
phone. Frequency
range 25- 1 3. 000c/ s.
With 5ft lead. Price
88/6. P. A P. 4/0.
Other similar types
available. AKAI AS ESS, S ohms, (6,8.0:
CORAL E 102, 10 ohms. (5.18.6: EAGLE
SB1, 10 ohms, 78/6. T.T.C. Stethoscope,
8 ohms, 48/6, P. ft P. 4/6 each.
TEAK FINISH
PLINTHS with perapex
cover 61 gns. (for LAB80
B f gns.). P. & P. 12/6
Agents for Tborens, Dual,
old ring, etc.
GARRARD DECKS
3000 wi th Sonotone 9TA HC Ste reo Cartrld ge . . (8.19.6
3000 with Sonotone 9TAHC Diamond Stereo
Cartridge 48.18.6
ATSO MKI less cartridge (10.19.6
ATSOMKTI less cartridge (If. 19. 6
AT 60 MKII with Decca Dcr.im Stereo Cartridge (17.14.0
SP. 25 MRU less cartridge (10.19.8
3P. -25 MKII with Decca Derani stereo Cartridge (16.14,0
AP.75 less cartridge (22, 11 .6
LAB.30 HKH less cartridge (£4.18.6
All plus P. 4 P. 12/fi
Mono Cartridge 17/ G extra.
Stereo Cartridge 22/S extra.
SAVE £2,2.0
Transistor FM tuner. Frequency range 88-
I08Mc/b. Sire 8 x 4 x 2iln. Beady built lor
use with most amplifiers, flv battery operation.
CompIete;wlth instructions. LIST PRICE 9 gns. SWttolM adaptor for Stereo Radio
L1ND AIR PRICE 7 gJlS. F. ft P. 4/-. Reception (6,18.6 extra.
8ARGAIINLOFFER! FANTAVOX CASSETTE TAPE PLAYER
Specially designed to replay the well known and
popular Mnslcasseltea— prerecorded tape cassette
offering a wide choice of all types of music from pop
to classical. Vp to 40 minutes of quality repro-
duction through built-in speaker. Simple off/play
and volume controls. Fully transistorised operating
on six peniight batteries. Modern compact styling
with earpiece socket and wrist strap. Size Si x
41 x 2in.
LTND AIR PRICE. £9.19.6. *"* -**» **
I us. 5/-.
COMPLETE HI-FI STEREO SYSTEM
ALL TRANSISTOR B
WATTS FEE CHANNEL
STEREO HI-FI SYSTEM
OFFERING A PERFOR-
MANCE EQUAL TO IF
NOT BETTER THAN
SIMILAR SYSTEMS
COSTING UP TO
DOUBLE THE PRICE.
-Modem styling plus ad-
vanced circuitry using
latest silicon transistors
throughout.
The famous GARRARD 3000 Record Changer fitted lightweight tubular arm with SONO-
TONE 9TAHC STEREO/MONO DL4M0ND CARTRIDGE will play all (lies of records.
(4 speeds "8, 45. 33 1/3, 16 2/3 r.p.m.l. Will play up to 9 records automatically, also pro-
vision for manual play. Amplifiers and controls are mounted below record player and Incor-
porate Bass, Treble, Volume and Balance controls and On/Off, Cram/Radio, Mono^Stereo
slide switches, TWO IDENTICAL LOUDSPEAKER SYSTEMS each Incorporating
separate bass speakers and high frequency units with crossover network provide full
frequencj- reproduction and are complete with 10ft leads and plugs for connection la
amplifier. Will fit easily on to bookshelves, room dividers or existing furniture. BRIEF
SPEC. Player/ Amplifier unit. Teak finish, size 18i x 14 K Slln 200/050V a.c. operation.
Inputs for Radio Tuner/Tape Recorder also outputs for Tape Recorder. Loudspeaker
Systems, Teak finish, size (each)l 3 x 7 x Sin. Supplied complete wltb Instruction booklet.
ready to plug in and plav. SEND YOUR ORDER NOW OR CALL AND HEAR THIS
MARVELLOUS HI-FI STEREO SYSTEM (Teak finish). Only 68 CM. plus 20/- Carriage
and Insurance. (Rosewood 3 gns. extra.) (Clear Ferepex Cover 3 gns. extra.)
LINEAR AMPLIFIERS
Latest i.e. mini Models offering highest duality
at moftest wnt. ...
LT68. All Transistor 12 watts Stereo. Inputs for
Tuner, Oram, Mike, Separate Bans, Treble,
Balance and Volume Controls (16.11,0. Carr. 7/0.
Teak case (3.10.0 extra.
PTA 16 (as lllus.l. All Transistor, 10 watts Mono.
Inputs for Tuner, Oram, Mike, (lullar, Bass. Treble
and two volume controls, (15.15.0. Carr. 7(6. Teak
case (8.10,0 extra. LT46, 2 Valve 6 watte Mono.
Inputs for Tuner, Gram, Bass, Treble and volume
over Uf~ extra. FuUdetallesent on request.
controls, (4.18.8. Carr, 7/6. Metal
317
20 WATT
SOLDERING
INSTRUMENT
CONTROLLED TEMPERATURE
Design holds max, temp, of 380°C.
within close limits.
• EASY BIT REPLACEMENT
Simple, fast replacement of low-cost
copper bits. Non-wearing PERMATIP
bits cut servicing costs.
# BEAUTIFULLY COMPACT
Length 7{*. Weight 1± 02.
Max. handle dia. 0.715"
# UNEQUALLED PERFORMANCE
Ideal for fast production soldering
on the majority of modern electronic
equipment.
• ALL VOLTAGES
The LITESOLD range includes six other
models (10, 18, 25, 30, 35 and 55 watts), and
many accessories. Please ask for colour
catalogue L'37.
LIGHT SOLDERING
DEVELOPMENTS LTD.
28 Sydenham Road, Croydon, CR9 2LL
Tel. 01-688 8589 & 4559
W" 1
FANTASTIC BARGAINS
SONOTONE
SOLENT
2 SPEAKER
HI-FI
SYSTEMS
# LIST £18 EACH
SPECIAL
OFFER
II gns.
# Impedance 8 ohm. Power input up to 12 watts.
Suitable for valve or transistor amplifiers.
Frequency response 40c/s to 20 k/cs.
Scandinavian style cabinet.
# Small attractive size 14 x 9 x 8 J.
# On permanent demonstration.
# Reviewed by Hi-Fi News, The Gramophone, etc.
Send large s.a.e. for FREE Leaflets and Test Reports available
from our Showrooms.
J. J. FRANCIS LTD.
123 ALEXANDRA ROAD
tONDON, N.8 BOW 1662
LEE ELECTRONICS
400 EDGWARE ROAD
PADDINGTON 5521
BUILD YOUR CIRCUITS
on
VEROBOARD
— the Universal Wiring Board —
obtainable from your local Retailer
Trade enquiries to :
NORMAN ROSE (ELECTRICAL) LTD.
8 St. Chad's Place, Gray's Inn Road, London, W C.I
Technical enquiries to:
VERO ELECTRONICS LTD.
Industrial Estate, Chandler's Ford, Hants
All items previously ad-
vertised available, alto see
item* advertised in Prac-
tical Wireless. Huge Hi-
Fi and Components stock*
at all branches.
ECHNICAL
TRADING
* PORTSMOUTH
(Tel. 22034)
150-352 Fratton Road
* SOUTHAMPTON
(Tef. 2S8SI)
n East Street
■*• BRIGHTON (Tel. 23975)
6 Queen's Road
all mail order Brighton
FANTASTICALLY POPULAR
TAPE
We offer yon fntly to utilised polyester/mylar
and P.V.C. tapes ol identical (.ntiity bi-fl, wide
range recording characteristics si ton grade
tapes. Quality oontrol msnufactnre. They
are truly worth s lew more coppers than
acetate, snb-staodard, jointed or cheap imports
TBY OKK AHD PROVE IT YOUKSELF.
Ems Am
3 in. 2251 '.. 2,9
tin. 450ft, SB
Sin. 900ft. 10/6
5ita. 1,200ft. 18/-
7in. j ,800ft. 18/8
Triple Play
tin. 900ft. 18/-
5in. 1,800ft. 26;-
5Jin. 2,400ft. 84/-
7in. 3,600ft, 44/-
Qnitdniple Pier
3in. 600ft. 8/8
Ptitttiget 1/- reW,
Post Free lets 5",. on three reels.
Quantity and Trade en fairies incited.
NOTE. Large tape *f«*» at alt branrhti.
Standard Play
am.
150ft.
M
4in.
300it.
*t*
Sic.
600ft,
7/8
Si in
900ft.
10/8
Tin.
1. 20Oft.
Double Play
12.6
3in.
300ft.
*l-
4m.
600ft.
tll-
4in,
l,200tt.
187-
4f:i
1 ,800ft.
19/8
At,
2,400ft.
27/-
318
PRINTED
CIRCUITS
Five assorted
printed circuit
boards with
transistors, diodes,
resistors, conden-
sers, etc, Guaran-
teed minimum
20 transistor?.
Ideal for experi-
menters. 5 boards
lot lit— ?■ * P-
2/-.
F.M. WIRELESS
MICROPHONES
94-104Mc/s. Transistor-
ised. Operates from 9 V
battery. Complete with
additional secret tie-clip
rnlcrophone.Ltst £12.10.0
ONLY «/15,'0. P. ft T.
216.
These cannot be operated
In U.K.
MODEL TE.80
20,000 O.F.V.
MULTIMETER
0/10/50/ 100/ 500/
1,000V B.C. 0/5/20/
oo/aeo/ 600/ i.ooov.
d.c. 0-50^ A 6/50/
000mA. O,'6,'60K/
60OK/6M{l.M/17/'8.
P. ft P. 3/-.
HEW MODEL EM
30,000 o.p.v, With
over Ion. d protection,
mirror scale 0-5/ 1/2 -5/
10/25 / 100 / 250 /6O0 /
1,000 V d.c.
0/2'5 / 10 / 25/100/250/
500/1.000V a.c.
0/50jiA/fl7 60 /500 mA
12A d.c.
o/eokh/sMn/eoMQ.
f8;17.r6. Post Paid.
MODEL Z0M TRANSISTOR CHECKER
It has the tallest capacity lor
checking on A, B and Ico.
Equally adaptable
checking d iodes, etc. Spec.
A:0-7-0-9B67. D: 6-200.
Ico: 0-60 mtcroamps
0-5mA. Resistance lor
diode 200(1 -1MB.
Supplied complete with
Instructions, battery and
leada.iS.M.S.P.ftP.2/6.
■lor
VARIABLE VOLTAGE
TRANSFORMERS
Brand New— fully Shrouded. Input 230V
60/60c/s. Output 0-260 V.
1A W.10.0
2-BA £8.15,0
5A 19,16.0
HA 114.10.0
10A £18.10.0
ISA 121.0.0
20 A 187.0.0
Post extra.
SILICON RECTIFIERS
800V P.I.V. 200mA 2/0
200V p.I.V. 6A 5/f
400V P.I.V. 3A 7/8
I.OOOV P.I.V. 5A 7/8
400V P.I. V. 8A 676
400VP.I.V.8A 7/8
I.OOOV P.I.V. 860mA 8/8
800V P.I.V. 600mA 6/8
800V P.I.V. 6A 7/8
400V P.I.V. 600mA 3/8
70V P.I.V. 1A 8/8
160V P.I.V. 186mA 1/-
150V P.I.V. 25A U/8
700V P.I.V. 100A 49/S
400V P.I.V. 3A (S.C.R.) 7/8
100V P.I.V. 6A (S.C.B.) 18/8
200V p.I.V. BA (S.C.B.) 15 6
400V P.I.V. 5A IS.C.R.) 17/0
Discounts for quantities. Post extra.
■k TRANSISTORISED FM TUB HE *
6 TRANSISTOR
HIGH QUA-
LITY TUNER,
SIZE ONLY 6tn
X 4in X 2)in.
8 I.F. stages.
Double tuned
dl scrim Id* tor.
Ample output to
feed most amp liners. Operates on V
battery. Coverage 88-108Me/«. Ready
built ready for use. Fantastic value for
money, SOW «/7/6. P. 4 P. 2/6.
STEREO MULTIPLEX ADAPTORS S gni.
AV0METERS
Supplied in ex-
cellent condition
fully tested and
checked. Com-
plete with prod*,
leads and Instruc-
tion!.
Model 47A
HUM
Model 8 118.
Model 9 £20. P. ft P, 7/6 each.
TE22 SINE SQUARE WAVE
AUDIO GENERATORS
Sine : 20c/s to
200 kc/s on 4
bands. Square:
20c/a to 30ke/B.
Output Imped-
ance 5,000 ohms,
200/250V a.c.
Supplied brand
new and guaran-
teed with Instruc-
tion manual and leads, £15. Carr. 7/6.
TE-20RF SIGNAL GENERATOR
Accurate wide
range signal gen-
erator covering
120kc,s — 260
Mc/s on 6 bands.
Directly cali-
brated. Variable
R.F. attenuator.
Operation 200/
240V a.c. Brand new with Instructions.
fl£/10/0. P. ft P. 7/6. S.A.E. for details.
LAFAYETTE TE-46 RESISTANCE
CAPACITY ANALYSER
2pf - 2,000
mid 2- ohms
200 megohms.
Also cheeks im-
pedance turns
ratio, insulation .
200/260 V a.c.
Brand Hew 515.
Carr. 7/6.
ARM 00 COMBINED AF-RF
SIGNAL GENERATOR
AF. 8 IKE WAVE
20-200,000 c/s.
Square wave 20-
30,000 c /,. O/p.
HIGH IMP. 21V
P/P 600 O 38V
p/p.
TF. lOOke/s-300
Mc/B.
Variable R.F. attenuation iul/ext. modu-
lation. Incorporates dual purpose meter to
monitor AF. output and % mod. on R.F.
220/240V a.c. £27/10/0. Carr. 7/8.
TE-65 VALVE VOLTMETER
High quality Instru-
ment with 28 ranges.
D.c. volts 1-5-1.500V
A.c. volts 1S-1.500V
Resistance up to 1,000
MB.
220/240V a.c. opera-
tion.
Complete with probe
and instructions. 118.
P. ft P. 6/-.
Additional ProWes
available: R.F. 35-
H.V. 42/8.
I catalogue
1 Electronic
i components
\ Equipment
t,f,)j\ 87/8
lOOuA 35/-
200)uA 82/8
600/itA 27/6
50-0-BO^A 85/-
10mA .
20mA .
.Win A .
1 00m A .
160mA . ,
CATALOGUE
ir ELECTRONIC COMPONENTS
* TEST EQUIPMENT
* COMMUNICATIONS
EQUIPMENT
* HI-FI EQUIPMENT
We are proud to introduce our first
comprehensive catalogue ol Electronic
Components and Equipment. Oyer 160
pages fully illustrated, lifting thousands ot
items, many at bargain prices. Free discount
coupons with every catalogue. Everyone in
electronics should have a copy.
CLEAR PLASTIC PANEL METERS
First grade quality Moving Coll panel meters available
cx-Btock. 8.A.E. for Illustrated leaflet. Discount for
quantity. Available as folio ws: Type MR 38 P, 1 21/32ln
square front * .
25/-
26/-
25/-
26/-
25/-
257-
26/-
26/-
, 86/-
85/-
1mA
29/8
ioo-o-ioojua sue
500-0-500 nA 25/-
1-0-lmA . . 25/-
1mA 85/-
2mA £57-
25/-
eooiiiA .
aooinA
flOOmA
750mA
1A d.c.
26/-
85/-
25/-
86/-
25/
26/-
26/-
. 26/-
. 25/-
. 25/-
2A d.c 257-
5A d.c 28/-
3V d.c 25/-
10V d.c. . . 26/-
2flV d.c. , . 25/-
30V d.c. . . . 26/-
100V d.c.
150V d.c.
300V d.c.
500V d.c.
750V d.c.
16V a.c.
50V a.c.
150V n.c.
300V a.c.
500 V a.c.
Meter
POST EXTRA. Larger sizes available — send for lists.
ADMIRALTY B.40 RECEIVERS
Just released by the Ministry, High quality 10 valve receiver,
manufactured by Murphy. Coverage in 5 bands fj50kc/B-3GMc/s.
I.F. 500kc/s. Incorporates 2 R.P. and 3 l.F. stages, bandpass
filter, noise limiter, crystal controlled B.F.O., calibrator, I.F.
output, etc. Built-in speaker, output for phones. Operation
150/230V a.c. Size 191m X 13£lo X 16in. Weight 114 lb.
Offered In good working condition, 222.10.0. Carr. 30/-. With
circuit diagrams. Also available B.41 L.F. version of above,
16kc,'s-7O0kc/s. 217.10.0, cirr, 30/-.
U N R-30. 4-BAIMD
COMMUNICATION
RECEIVER
Covering 560 Kc/a — 30 Mc/s. Incorporates
variable BFO for CW/SSB reception. Built-
in speaker and phone Jack. Metal cabinet.
Operation 220/240 v. A.C. Supplied brand
new, guaranteed with A ,*i ia n
Instructions. tll.W.V Carr. 7/6
HEW LAFAYETTE MODEL HA -700 AM CW
88B AMATEUR 0OMMUFICATIOK RECEIVER
8 Valves, 5 bands Incorporating 2 MECHANI-
CAL FILTERS for exceptional selectivity and
sensitivity. Frequency coverage on 6 bands
160-400 kc/s 650-1 ,600kc/s, 1-6-4-OMc/e,
4-B-14-5Mc/s 10-6-30Mc/s. Circuit incorpor-
ates R.F. stage, aerial trimmer, noise limiter.
B.F.O. product detector, electrical baudspread,
H meter, slide rule rlial. Output for phones, low
to 2k O or speaker 4 or 80- Operation
220/240V a.c. Size 7jln X 15fn * lOin.
Supplied brand new and guaranteed with hand-
book 36 0H8. Carr. 10/-. S.A.E. for leaflet.
R.C.A. AR88 SPEAKERS
Sin, 3 ohm speakers In metal case.
Black unickle fin lab to match our
88 Receivcra, Available Brand
New and Boxed with leads.
59/8. Carr. 7/6.
LAFAYETTE U-224T TRANSISTOR STEREO AMPLIFIER
19 transistors, 8 diodes, ]HK munis
power, 30W at 8(1 . Response
30-20,000 ± 2dB at 1W. Distortion
1% or less. Inputs 3MV and
250MV. Output 3-1611. Separate
L. and R. volume controls. Treble
and bass control. Stereo phone Jack.
Brushed aluminium, gold anodlsed
extruded front panel with compli-
mentary metal case. Size 10 tin X
3&x7fttn. Operation 115,230V
a.c. £25, Carr. 7/8.
SINCLAIR EQUIPMENT
Z.12 12 watt amplifier, 89,6, PZ4
Power Supply Unit, 99/6. Stereo £5
Preamp.. 29.19.6. 0.14 Speakers,
18.19.6. Mieromatie Radio Kit, 49/8.
Hull!. 59 6, Micro PM Hadiij Kit.
15.19.5.
ALL POST PAID
SPECIAL OFFER
2 Z12 Amps., PZ4 Power
Supply. Bterao 26 Pre-
amplifier, 122.
I (RADIO) LIMITED
2 Phone: GERRARD 8204/9155
__T Cables: SMITHEX LESQUARE
3-34 LISLE STREET, LONDON, W.C.2
319
POCKET MULTI-METER
Size 31x2ix l£in. Meter siJ.e 2J :-: ljin. Sensitivity
1000 O.P.V. on boih A.C. and D.C. volts. 0-15,
0-150, 0-1000, D.C. current 0-1 50mA. Resistance
0-100kfi. Complete with test prods, battery and full
instructions, 42/6. P. & P. 3/6. FREE GIFT for
limited period only. 30 watt Electric Soldering Iron
value 15/- to every purchaser of the Pocket Multi- Meter.
3 to 4 WATT AMPLIFIER
3-4 watt Amplifier built and
tested. Chassis size 7 X li X I in.
Separate bass, treble and volume
control. Double wound mains
transformer, metal rectifier and
output transformer for 3 ohms
speaker. Valves ECC8I and 6v6.
£2.5.0 plus 5/6 P. & P,
BSR TAPE DECKS
200/250 v. A.C. mains. Type TD2
Tape speed H twin track. Type
TD10 2-track, 3 speed, plus rev.
counter. Type TD10 4-track, 3
speed, plus rev. counter.
Due to 33j"„ Purchase tax wlitch is rvnw
applicable on these Items, prices will he
announced as soon as available.
Special offer ELEGANT SEVEN
SPECIAL OFFER. Power supply kit to
purchasers of 'Elegant Seven' parts, incorporating
mains transformer, rectifier and smoothing con-
denser, A.C, mains 200/250 volts. Output 9v. 100
inA. 9/6 extra.
Buy yourself an easy to build 7 transistor radio and
save at least £1 0.0.0. Now you can build this superb
7 transistor supernal radio for under £4.10.0. No - ONLY
one else can offer such a fantastic radio with so +/\ a ft
many de luxe star features. B*w • W • 9
it De luxe wooden cabinet site 12i" x «T x 3±". fl^7.6Post&Pa<:king
ie Horizontal easy to read tuning scale printed grey with black letters,
size 11;" x 2". it High 'Q' ferrile rod aerial. it IF neuttalisation on
each separate stage. it D.C. coupled push pull output stage with
separate A.C negative feedback, if Room filling output 350mW.
■+■ Ready etched and drilled printed circuit board back printed for
foolproof construction, it Fully comprehensive instructions and point to
point wiring diagrams, ic Car aerial socket, it Fully tunable over medium
and longwave, 168-535 metres and 1250-2000 metres. -A* All components.
ferrile rod and tuning assembly mount on printed board, it 5' P.M.
Speaker, it Parts list and circuit diagram 2, 6, tree with parts.
(music power).
X101 10 WATTS (RMS) SOLID-STATE HI-FI
AMP. WITH INTEGRAL PRE-AMP
Its great versatility ranges from: a simple
intercom, to a modern HI-FI STEREO
AMPLIFIER (two are required for Stereo).
The XtOI is a brilliant new addition to our
highly successful range of products. Its
professional performance and advanced
solid-state circuitry techniques ensures
reliability, combined with high fidelity
reproduction, at an unbeatable price of
49/6 + 2/6 P. & P.
SPECIFICATIONS: R.M.S. Power Output.
I0W (SINE WAVE). Sensitivity: for rated output ImV into 3k£2
load. Frequency Response: minus 3dB points are 20Hz and 40kHz.
Total Distortion: at I kHz; for rated output I -5%; for 5W output
0'35%. Output Impedance : 3 ohms (3-15 ohms may be used). Supply
Voltage : 24V d.c. at 800mA (6-24V may be used) ; output at
I4V d.c. supply with 3 ohms speaker 7W. Size; 2|in 3in •,: 1 -ft in.
The fully comprehensive instruction manual does not only show the
basics, such as circuit diagram and connections, but also gives practical
easy-to-understand detailed information about the X101. Standard
equalisation networks are given for most types of conventional
inputs. They include; Tape head, Mag. P.U., Xtal. P.U., Tuner, Mie, etc.
CONTROL ASSEMBLY. (including resistors and capacitors) :
I. Volume, price 5/-; 2. Treble, price 5/- ; 3. Comprehensive
bass and treble, price 10/-.
POWER SUPPLIES FOR THE X101 : P10I/M (for Mono) 35/-
P. & P. 2/6. P10I/S (for Stereo) 42/6 P. & P. 2/6.
PRIGI/M : A High Quality, Monoral P re-amp and Control Unit,
particularly suitable for use with the XI01 if a ready-built,
comprehensive, multi-input system is desired.
CONTROLS; Selector Switch, Tape Speed Equalisation Switch (3j and
?i I.P.S.), Volume. Treble, Buss, three position scratch filter and
three position rumble filter,
SPECIFICATION : Sensitivities for 200m V output at \kHz, Tape Head :
3mV(at3JI.P.S.). Mag. P. U.: 2m V. Cc r, P. U. : 80mV. Radio: lOOmV,
Aux. : lOOmV. Tape/Rec. Output; lOOmV. Equalisation for each input
is correct to within = 2dB (RIAA) from 20Hz to 20kHz. Tone Control
Range: Bass: ± I3dB at 60Hz; Treble: l4dB at l5kH?. Total
Distortion: (for 200mV output) < 0-02";. Signal Noise: > — 60dB.
Supply Voltage: 24V, d.c. 59/6 plus 2/6 P. & P. A STEREO
VERSION (PR101/S) WILL BE ANNOUNCED SHORTLY.
THE CLASSIC: High Quality Solid-State Amplifier (Mono).
SPECIFICATION: Switched inputs for: Tape head. Mag. P.U.. Cer.
P.O.. Radio and Aux. Mains Input 220-250V, a.c, 50Hz. The Classic
is the combination of the above described items (X10I.P10I/M and
PR 101 /M) on one common chassis. Its performance and space age
styling makes if the ideal choice for the value-conscious Hi-Fi enthusiast .
8 gnS. P. & P. FREE.
STAR SR 150 COMMUNICATION RECEIVER
Frequency range: 535 kc/s-30 Mc'/s.
four wavebands, four valve plus
metal rectifier superhet circuit. In-
corporates B.F.O. bsndspread
tuning, "S" meter, external telescopic
aerial— ferrite aerial, built-in 4"
speaker, easy-to-read dial. For240v.
A.C. operation. Complete, brand
new, with full instruction manual.
£17.17.0. P. &P. 10/-.
600 mi Hi- watt solid state
7. transistor plus diode
and thermistor
NEW! DORSET
Transistor Portable Radio
plus Baby Alarm Facilities
Special offer— Power Supply Kit to
purchasersof Dorset Portable Radioparts,
incorporating mains transformer, rectifier
and smoothing condenser, A.C. mains,
200/250V., output 9v., 100mA. 9/6 extra.
Completely modulised high quality port-
able radio featuring complementary
N.P.N, and P.N.P, output stage.
The comprehensive easy-to-follow drawings supplied make this
the easiest-ever transistor radio set of parts, with the following
features:
• Simple connections to only 6
tags on the R.F./I.F. module,
3 I,F, stages, osc. coil and 3
transistors which with their
associated components are
completely wired.
# Only 4 connections on the A.F.
module to complete the 4 tran-
sistor 600 milli-watt solid state
amplifier.
# Pre-aligned R.F./I.F. module
built and tested.
9 A.F. module built and tested.
# Fully tunable over M.W. and
L.W. bands. M.W. 540-1640
Kc/s (557-183 metres). L.W.
150-275 Kc/s (2000-1 100
metres).
• Intermediate Frequency 470
Kc/s.
• Sensitivity, M.W. at 1 Mc/s 10
microvolts plus or minus 3db.
L.W. at 200 Kc/s 40 microvolts
plus or minus 4db.
• High Q internal ferrite rod
aerial on both wavebands.
9 Class "B" modulised output'
stage with thermistor controlled
heat stabilization. Class "B"
output stage ensures long
battery life. Current drain is
proportional to the output level.
Total current drain of the
receiver under no signal con-
ditions is 10- 1 2mA. At reason-
able listening level 20-30mA.
# Extension sockets for car aerial
input, tape recorder output
(independent of vol. control)
and Ext. Speaker.
% All components(except speaker)
mount on the printed circuit
board. Easy to follow instruc-
tions. Size of cabinet 12" long,
8* high and 3" deep.
Finger tip controls.
Circuit and parts list 2/6, free with
parts.
PRICE: £5*5*0 plus 7/6 P. ft P.
FIRST QUALITY P.V.C. TAPE
$f
Std. 850ft.
. 9/- 5' L.P. 850ft. . . 10/6
:■■
Std. 1200ft. .
11/6 3" T.P. 600ft. .. 10/6
r
L.P. 240ft. .
41- 5" T.P, 1800ft. . . 25/6
w
L.P. 1200ft. .
. 11/6 51" T.P. 2400ft. .. 32/6
V
L.P. 1800ft. .
. 18/6 7" T.P. 3600ft. . . 42/6
5f
D.P.I 800ft. .
. 18/6 4" T.P. 900ft. . . 15/-
P. & P. on
each If 6, 4 or .more post free
600m W SOLID STATE
4-TRANSIST0R AMPLIFIER
Speaker output impedance 12 ohms.
90 c/s and 12 Kc/s. Price 19/6 plus 1/-
13/6 plus 2/- P. & P.
Features NPN and PNP
Complementary Sym-
metrical Output Stage.
Size: .24" x l" x J*
Frequency response 3db points
P. & P. 7"x4" speaker to suit.
2i WATT ALL TRANSISTOR AMPLIFIER
AC mains 240v, Size 7" x 4±" x 1 J". Frequency response 100 c/s — 10
Kc/s. Semiconductors, two OC 75's, two AC 128's and two stabilisers
AA129. Tone and volume controls on flying leads. £2.10.0. P. & P.
3/6. Suitable 8* > 5" 10,000 line high flux speaker 18/6. P. & P. 2/-.
Available within 4 weeks.
8-WATT 4^ALVE PUSH-PULL AMPLIFIER & Metal RECTIFIER
Size 9" x 6" x 1 i". A.C. Mains, 200-250 v. 4
valves. For use with Std. or L.P. records,
musical instruments. All makes of pick-ups
and mikes. Output 8 watts at 5 per cent of
total distortion. Separate bass and treble
lift control. Two inputs, with controls for
gram, and mike. Output transformer tapped
for 3 and 15 ohm speech coils. Built and tested. £4.4.0. P. & P. 11 /-.
8* x 5" Speaker to suit. Price 14/6 plus 1/6 P. & P. Crystal Mike to
suit 12/6 plus 1/6 P. & P.
-1-9-9-**
RADIO AND T.V. COMPONENTS (ACTON) LTD.
21 D HIGH STREET, ACTON, LONDON, W.3
Shop hours 9 a.m. lo 6 p.m. Early closing Wednesday
Goods not despatched outside U.K.
Alt enquiries stomped addressed envelope. Terms C. W.O.
Alio at 323 EDGWARE ROAD, LONDON, W.J.
PERSONAL SHOPPERS ONLY. Early closing Thursday,
All orders by post must be sent to our Acton address.
320
rfg=^ Now available
Mmiard 1 1968 Data Book
^S
1 36 pages of data, including for the first time, colour-coded
sections for quick reference — covering comparables and equivalents
and all current Mullard semiconductors, valves, tubes and compon-
ents for Radio, TV, Audio and HiFi applications.
PRICE 3j6 from your local TV retailer OR direct from Milliard — cash
with order, plus 9d for pr and p.
Mullard Limited, Distributor Sales Division,
Mullard House, Torrington Place, London, W.C.1 .
Mullard
TRANSISTOR
STEREO 8 + 8
A really (lrat-claai Hi-Fi Stereo Amplifier KM. Uses 14 transl stars giving
8 -watts push-pull output per channel, (IB W mono}. Integrated pre-amp
with Bass, Treble and Volume controls. Suitable lor use with Ceramic or
Crystal cartridges. Output stage lor any speakers from 3 to 16 ohm?.
Compact design, all parts supplied including drilled metal
work, Clr-Klt board, attractive front panel, knobs, wire,
, a solder, nuts, bolts — nn extras to buy. Simple step by step
instructions enable any constructor to build an amplifier to
be proud of.
Brief Specification: From response = 3 db 20-20,000 c,s.
Bass boost appro*, to +18 db. Treble cut approx, to
— IB db. Negative feedback IS db over main amp.
Power requirements 2a V at 0'fl amp.
PRICES
Amplifier Kit
Built and Tested
Power Pack Kii
Built and Tested
Cabinet (as illui.j
£9.10.0
£12.10.0
£2.10.0
£3.0.0
£2.10.0
& P. 4,6
, & P. 4, 8
. 4 P. 4,'-
& P. 4>
, ft p. s, e
(Special offer — £14.10.0. Post 1'ree if all above kits
ordered at same time or can be supplk'.l buiit and tested
tor £18.0,0 Post Free),
Circuit diagram, construction details and parts list (free
with kit) 1/6 (S.A.E. >
STEREO AMPLIFIER
Incorporating 3 ECLSos and 1 EZ60. heavy duty,
double wound mains transformer. Output 4 watts
per channel. Full tone an d voj ume controls. Alisolutely
complete.
ONLY
£5.9.6
P.1P.5/-
luper De-
nse version
with ECLS6
valves, sep.
bast, treble anil balance con-
trols. Full feedback. 8 gnt,
P. A P. 8,'-.
HIGH GAIN 4 TRANSISTOR
PRIN TED C IRCOIT
AMPLIFIES KIT
Type TA1
• Peak out-
put In excess
of 11 watts.
• All stan-
dard British
components.
• Built on
printed circuit panel size 6
• Generous size Driver and Output Transformers.
• Output transformer tapped for 3 ohm and 15 ohtn
speakers. • Transistors- (GET 114 or HI Mullard
OCB1D and matched pair of OCB1 o/p). • 9 volt
operation. • Everything supplied, wire, battery clips,
solder, etc. 9) Comprehensive easy to follow instructions
and circuit diagram 2/8 (Free with Kit). All parts snl.l
separately. SPECIAL PRICE 45/-. P. & P. 3j: Also
ready built and tested, 52/6. 1'. ft P. 3,'-.
FM.'AM TUNER HEAD
Beautifully designed and pre-
cision engineered by Dormer
and Wadsworth Ltd. Sup-
plied ready fitted with twin
-0003 tuning condenser for
AM connection. Prealigneil
FM section covers 86-102Mc/s.
I.F. output 10-7 Mc/s. Com-
plete with ECC8S <6L12) valve
and full circuit diagram of
tuner head. Another special bulk purchase enable* us
to offer these at 87/6 each. P. & P. 3/-. Order quickly 1
HATCHED PAIR AM/FM I.P.'s. Comprising 1st I.F. and
2nd I.F. discriminator, (465 Kc/s/10-7 Mc/s). Hize
lln.xljin. :-2Jin. M. Will match above tuner head.
11/- pair. P. & P. 2A .
GORLER P.M. TOTTER BEAD. H5-KJ0 Mc.s 10 7 Mc/s.
I.F., 15/-, Plus 2/6 P, * P. <ECC85 valves, 8/6 extra. 1
S.T.C. SILICON AVALANCHE HALF-WAVE RECTI-
PDXRS. Type BAS. 508 AF. 6 amps. 560 P.I.V. lin. long
X iin. dia. approx. List 50/-. OUR PRICE B/6. P. Free.
SPECIAL OFFER ! PLESSET TYPE 29 TWDI TUKBIG
GANG, 400 pt + 146 pf. Fitted with trimmers and 8:1
Integral slow motion. Suitable for nominal 470 kc's. I.F
Size approx. 2"x l'Xl}'. ONLY 8/8. 1". & P. 2/6.
PEW OHLY : SIEMENS MINIATURE RELAYS. D.P.C.O.
Gold plated contacts. Size approx, Ij* X i" XI i". 8».
at 30 niA. ONLY 15/-. P. fc P. 1/B.
NEON A.C. MAINS INDICATOR. For panel mounting, cut
out size 1 1 X I X lin. deep inc. terminal. White case with
lens giving brighter light. For mains 200/250v. 2/8 each.
P. g P. 6d. (6 or more post free).
VIBRATORS. Large selection of 2, 4. 6, 12, 24 and
32 Volt. Non-sync. 8/8; Sync. 10/-, P. A P. 1/6 per
■vibrator. S.A.E. with all enquiries.
3-VALVE AUDIO AMPLIFIER MODEL HA34
Designed for HI-FI reproduc-
tion of records. A.C. Mains
■iperation. Ready built nn
plated heavy gauge metal
chassis, size 7;tn. w. -. 4in.
d. x 4Jin. h. Incorporatcs
EOC83, EL84. EZ80 valves.
Heavy duty, double wound
mains transformer and output
transformer matched for
3 ohm speaker, separate Ban, Treble and volume controls.
Xegatlve feedback line. Output 4J watt*. Kront panel
can be detached and leads extended for remote mounting
of controls. Complete with knobs, valves, etc.. wired and
tested for oidv £4,5.0. P. It P. 6/-.
HEL " FODR ■ AMPLIFIER KIT.' Simitar In appearance
to HA34 above but employs entlrelv different an- 1 ad-"
vaoced drcuitry. Com plete set of parts, etc, 79/6. P.* P. 9/-
16,14 WAH Hf-h
AMPLIFIER SIT
A Btyllshly finished
monaural amplifier
with an output of
14 watts from 2
ELS4a in push-pull.
Super reproduction
of both music and
speech, with neg-
ligible hum. Sep-
arate inputs for
mike and grain
allow records and
announcements d
follow each nthcr. l'"«iJI^ phr-mli-'! sovilcrtl 'w.uwt output
transformer to malLih 3-lifl speaker and 2 Independent
volume controls, ami separate bass and treble controls arc
provided giving good lift and cut. Valve llnn-up 2 ELMs.
KCC83, EK«i|. and EZH0 rectifier. Simple instruction
booklet 8,6. i t'n-c with parts.) All parti sold separately.
ONLY 17.9.8. I'. .V 1'. 8/8. Also available ready built
aad tested iiimjil,!,' with' std. input sockets, £9.5.0.
MAINS TRANSFORMER, l-'nr iian-i-'.:i yen:-, supplies.
Pri. 200/24(lv. Bus. 9-<t.'.i at 300 niA. 11/-. P. <t P.2/B.
Pri. UO0/240V. Sec. 12-U-I2 at I amp. 14/6. P. & P. 8/6.
MAINS TRANSFORMER. I'm- transistor power supplies.
Tapped pri 200-230V. Bee 40-0-40 at 1 amp (with
electrostatic screen) and S-3v, at -C amp fur dial Inmpsctc.
Drop thro* mounting, tftnek sine IJIn, Sfta. Ulin.
£7/8. P. & P. 4/6.
MATCHED PAIR OF Bl WATT TRANSISTOR DRIVER
AND OUTPUT TRANSFORMERS. Stack size 1 ' U ■
- in. 'Output trans, tapped for 3 ohm and 15 ohm out-
put. 10/- pair plus 2/- P, U I*.
PARMEKO 7-10 wait OUTPUT TRANSFORMERS In
match pair of ECL «2's in push-pull. Sec Lapped 3-7u.
- - and is.ihm. Stack tin: Sl'xl'XS* approx, osi.v
12 ■
r. &
•A ■.
7-10 watt OUTPUT TRANSFORMERS to match pair of
ECL Hfi's In push-pull lo 3 nhm output. OSLV 11'-
p. & i: 2/6.
10-12 wait OUTPUT TRANSFORMERS. Mm llln. tat
I'lamp rilting. For Iwo EL84 - s in push-pull. Slate 3 oi
iaohtn iinpL-danw. 18,8. P. * P. 2/6.
ACOS HIGH IMPEDANCE CRYSTAL STICK MIKES
Listed at 42.-. Our price, 21.-. 1: & P. 1 H.
ACOS CRYSTAL MDXES. High im p. For desk or ha ml usf
High sensitivity, 18,8. P. * P.
1/0.
SPECIAL OFFER: MOVING
COIL MIRE. Fmed on/ofl
switch tor remote control. High
Huallty. High or Low impe-
dance. (State Imp. rend.)
BARGAIN PRICK 30/-.
P. A T. 3/6.
LATEST COLLARO MAGNAVOX 363 STEREO
TAPE DECK. Three speeds, 4 track, iakes up to 7in,
spools. BD2.10.0. Pius 7/B t'arr. & ins. (Tapes extra),
B.S.E. TD.2. 4 track Stereo Tape Deck. Dgns. Carr. 7. 6.
aUALITY PORTABLE TAPE RECORDER CASE. Brand
new. Beautifully made. Only 49/6. P. i P. 8/6- Deal
Purpose Bulk Tape Eraser and Tape Head Demaanetiaer
35.'-. P. Is P. 3/-.
4-SPEED RECORD PLAYER BARGAINS
Mains models. Ail brand new in maker's original
packing .
LATEST B.S.R. MODELS
TB 12 Single Player with mono Cart £3.8.8
GD7 Sinele Player with mono Cart. £4.18.8
OA85 Changer with mono Cart 16.7.6
All plus Carriage and Packing 6 6.
Sea below lor suitable stereo cartridge !
LATEST OARRARD MODELS
ALL types available 1000, SP25. 3000, AT60, etc.
Sena S.A.E. for latest Bargain Prices I
BRAND HEW CARTRIDGE BARGAINS : LATEST B.S.R.
X3M MONO COMPATIBLE CARTRIDGE
With (turnover sapphire styli suitable for playing 78, EP,
LP and Stereo records with mono equipment.
ONLY 22/8. P. & P. 1/6.
SON0TONE 9TAHC Compatible Stereo Cartridge with
diamond stylus 50/- or with sapphire stylus 40/-.
1*. & P. 1,'ti each.
QUALITY RECORD PLAYER AMPLIFIER
A top-quality record player amplifier employing hcavy
iluty double wound mains transformer, ECCS3. ELo4,
K2y0 valves. Separate Bass, Treble and Volume
contrt.de. Complete with output transformer matched
fnr 3 nhui speaker. Size Tin. w. :< 3in. d. X fiin. h.
Kendy built ami tested, PRICE 75,'-. P. & P. 0/-.
ALSO AVAILABLE mounted rm board with output
transformer and speaker ready to fit into cabinet below.
PRICE 97/6. V. ,t P. 7,'ij.
DE LUXE QUALITY PORTABLE R/P CABINET
Uncut motor Ward size 14} in. :.; 12in. clearanee 2in.
below, oiin. above. Will take above amplifier and any
B.S.R. or GARKARD Autochanger or Single Player Cnif
(except AT60 and SP2a). Size ISin. :•: I Sin. < Sin.
PRICE £3,9.6. P. li P, 9/fi.
VYNAIR AND REXINE SPEAKER AND CABINET
FABRICS iipp. 54in, wide. Usuidly 85/- yd,, our price
13/6 per vd. length., P. & P. 2/6. (miu, 1yd.). S.A.E £or
samples.
BRAND NEW 3 OHM LOUDSPEAKERS
Sin.. 14/-; 6. '.In. ,18/6; 8Iti.,27/-; 7in. x 4in. 18/6; lOin.
i 6in., 27/6.
E.M.l. Sin. : oin, with high fluK magnet JS1,'-,
E.M.I. 131ln. . Sin. with high flus ceramic magnet, 42/-.
{15 ohm, 48/-). P. & P. 5in. 2.'-, eiSn. i Bin. 2/6, lOin. *
121n. 3-6 per s peaker.
BRAND NEW. 12in. tow. H/D Speakers, 3 or 13 ohfll.
Current production by well-known British maker. Offered
below list price at 89/6. P. & P. 5/-. Cultar mode's:
25w. 15.5.0; 35w. £S.8.0.
E.M.I. 3! in. HEAVY DUTY TWEETERS. Powerful
ceramic magnet. Available in 3, 3 or 15 ohms. 15/-.
P. AM'.
2'B.
ISin. "RA"
peak output.
31j.i. 12 8;
TWT5 CONE LOUDSPEAKER. 10 watts
3 i t 15 ohm. 36/-. P. & P. 3/6.
35 OHM SPEAKERS
41s. 21 -. P. Jc P. 2/- per speaker.
HARYERSON SURPLUS CO. LTD.
170 HIGH ST., MERT0N, S.W.I 9 01-540 3985
Open all day Saturday Early closing Wed., I p.m.
A few minute* from South Wimbledon Tube Station , tP/eose write clear if)
OVERSEAS P. A P. CHARGED EXTRA. S.A.E. with all enquiriai
32t
OUTSTANDING HIGH FIDELITY
DESIGNS FROM SINCLAIR
The
world's
smallest
radio
SINCLAIR MICROMATIC
The ultimate in personal listening, the Micro-
matic is as easy to have with you as your wrist-
watch. It has enormous power and range, and
the magnetic earpiece now supplied assures
marvellous quality. Hear how Radio 1 and other
stations simply pour in. Build it yourself or buy
your Micromatic ready bulit. This is the set you
will never be without once you hear it for yourself.
• H' I &■ » r
Q Tunci over medium
waveband
# Slow motion tuning
control
£ Aluminium front
panel and dial
9 H agnatic tar piece
Complete kit including
innfucliom
49/6
Read/ built with
magnetic eorp/ece
59/6
tAoUory Mercury Ce"
RM.67S (2 needed)
each 1/9
SINCLAIR
Q.I4
LOUDSPEAKER
BRILLIANTLY EFFICIENT
. . . especially in stereo
When Sinclair Radionics decided to design and manufacture a new loud-
speaker, it was required from the start that its performance should be worthy of
today's best high fidelity standards and be so reasonably priced thatthe greatest
numbers could afford it. By using ultra-low resonant materials to form its
acoustically contoured housing, outstandingly brilliant performance resulted.
Furthermore, the unusual form of the Q.14 meant It could be used as a free-
standing shelf speaker, as a wall-corner sound radiator or flush mounted
singly or in multiple units on a flat surface such as a wall. The correctness of
the design of the Q.14 has amply proven itself since within a few months of its
introduction, It is already amongst the four most demanded loudspeakers
irrespective of price. Independent laboratory tests have already shown thatthe
0,14 has amazingly good performance characteristics. As a judge of good
sound yourself, your ear will confirm this instantly. At its price, there is nothing
to stop you changing to Sinclair at once.
• Size 9 V i n x 9|in x 4|in
deep plus detachable base
• IS ohms impedance
• Up to 14 watts loading
• Smooth response between
60 and 16,000 Hz
• British manufacture
The Q.14 is finished in matt black with solid
aluminium bar embellishment on the front.
Supplied in strong fitted carton and sent
post free under money back guarantee if
you are not satisfied.
IDEAL WITH Z.12 HI-FI SYSTEMS
SINCLAIR RADIONICS
Cambridge
►
LTD., 22 Newmarket Road,
Phone OCA-3 52996
322
SINCLAIR
UNCHALLENGED LEADER IN ITS FIELD
COMBINED 12 WATT HI-FI AMP AND PRE-AMP
No constructor's transistor amplifier has ever achieved such success
as the Sinclair Z. 12. it favours the user in so many ways— with fantastic
power-to-size ratio, with far greater adaptability, with freedom to
operate it from batteries or mains power supply unit (the new PZ.4 is
ideal for this) with the opportunity to obtain superb stereo reproduction
for very little outlay. Countless thousands of Z,12s are in use through-
out the world— in hi-fi installations, electronic guitars and organs, P.A.
installations, intercom systems, etc. This true 12 watt amplifier is
supplied ready built, tested and guaranteed together with the Z.12
manual which details control circuits enabling you to match the Z.12
to your precise requirements. For complete listening satisfaction, use
your Z.12 system with Q.14 loudspeakers. It assures superb quafity
with substantial saving in outlay.
• 3" x fi' x U"
• Class B Ultralinear output
• 15-50,OOOHz ± 1dB
• Suitable for 3, 5, 8 or 151*
speakers. Two 3-ohm speakers
may be used in parallel.
• Input— 2mV into 2k t'
• Output— 12 watt, R.M.S.
continuous sine wave
(24W peak)
YOUR SINCLAIR
GUARANTEE
Should you not be completely
satisfied with your purchase when
you receive it from us, your money
will be refunded in full at once and
without question. FULL SERVICE
FACILITIES AVAILABLE TO
ALL SINCLAIR CUSTOMERS.
"/ made this (Z.12} stereo record player
for my work as hospital chaplain and it
has been a great success."
K.S.B. Basingstoke
"The Z.12 and Q.14 live up to your
high standard. I could spend pages
praising these products."
I.A.W. Hereford.
Ready built,
tested and
guaranteed.
89/6
For use with two Z. I2's or any good hi-fi stereo
system. Frequency response 25 Hi to 30kHzJ- IdB
connected co two Z.I2's. Sensitivity Mie.2mVinto
50k Q ; P.U. -ImV into 50k R : Radio — 20m V into
4.7k n. Equalisation correct to within :: IdB on
RIAA curve (rem 50 to 20,0O0Hi. With brushed
and polished aluminium front panel with solid
aluminium knobs to match. Size 6)inX2JinX 2lin
plus knobs.
BUILT
TESTED
AND
GUARAN-
TEED
£9.19.6
SINCLAIR PZ. 4
STABILISED POWER SUPPLY UNIT
A heavy duty a.c, mains
power supply unit deliver-
ing 18V d.c. at 1-5A. De-
signed specially for Z.12
assemblies.
Ready built
and tested.
99/6
WE PAY POSTAGE ON EVERYTHING YOU ORDER
To: SINCLAIR RADIONICS LTD., 22 NEWMARKET ROAD, CAMBRIDGE
Please send POST FREE
For which I enclose cashicheque/money order
I tor which I enclose cast,
I
NAME.
ADDRESS.
PE,5
323
DONT MISS THIS
Lasky's Birthday Draw f " EASI-TUNE '* AM/FM MAJOR
The to! lowing 85 number* bare been drawn lor prim in our 3Stb Birtbdij Dnw.
PImm refer to Pige 12 at our Catalogue tor oolaili ol entry il jonr number (on tbe
iron! psge ol roar Catalogue) It among thoM lilted here :
GMT17
000013
001415
002313
012603
024444
028688
oooose
001510
002414
012777
024818
028875
mat
001582
O0S47S
013828
024850
028800
0OG89S
001711
003080
013750
028516
028989
000827
001777
003183
015000
027000
030138
OOO0S9
001800
004000-
oieooi
027008
030744
000874
001800
005016
018020
028010
030S44
001054
ooien
005IS1
020003
028456
030882
001274
001922
005815
021414
028480
031010
001288
O01B81
008788
021444
028030
032013
001282
002101
003900
021500
028131
033417
001333
002230
011717
023486
029444
034111
038000
037017
636111
038212
039414
039S85
043472
048792
047111
037388
048001
The Brit 10 correct entries to be opened will receive tb Laiky'j Gift Voucher i,
tbe next 25 will receive f 1 raucheri end tbe next 50 will receive 10/8 vouchers.
Note; Humbert of Lotly't Radio itaff n„it rektirti ate rxprei*lv excluded from
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CROWN MODEL TRF-6 AM/FM
9 TRANSISTOR RADIO
Unbelievably small for an AM,' KM receiver— the
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styled and finished cabinet in black plastic with
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t'flniplcte with leather purse, ear-piece and battery.
Lilt Price 13 i Gnr.
SCOOP Price £7.19.6 imw
MODEL C-I000 MIL! TESTER
A really liny meter with "big" meter performance. Brief Specifica-
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Branches
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Open all day Thursday, early closing 1 p m Saturdav
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High Fidelity Audio Centres
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ALL MAIL ORDERS AND CORRESPONDENCE TO: 3-15 CAVELL ST., TOWER HAMLETS, LONDON, E.I Tel.: 01-790 4821
324
VOL. 4 No. 5
May 1968
PRACTICAL
ELECTRONICS
LABOUR OF LOVE
Te trouble with certain amateurs" we heard a well
known professional recently complain, "is that
they make things far too good". This was a mild
protest at the fastidious concern for detail and elabora-
tion indulged in by some spare time constructors.
In expressing this opinion, this critic certainly revealed
his awareness of amateurs, and indirectly paid tribute
to the high standard of craftsmanship often found
amongst the non-professionals. This is certainly
gratifying. In all walks of life too much distinction is
maintained between the amateur and the professional.
In general parlance the term professional, when applied
to person or product, suggests superiority. Quite
commonly it is assumed -that the amateur represents
merely the second best.
The activities and achievements of individuals in
fields outside their normal vocation are often belittled
without just cause. Resentment of outsiders poaching
upon their exclusive preserves, plus a feeling of in-
security or even of inferiority (unadmitted, of course)
may be contributory factors for the patronising manner
adopted by some professionals towards their amateur
brethren.
So far as our own particular field of interest is con-
cerned, we have occasionally encountered such attitudes
from individuals professionally engaged in the
electronics industry. Happily such cases are the rare
exception. Many of our most esteemed friends and
associates are in the industry. Professionals they may
be, but also real amateurs at heart. For what does the
word really mean but a lover, or devotee. Genuine
interest and high proficiency in a subject (whatever it may
be) should not be automatically nor exclusively equated
with professionalism. Let's face it, there are good
and bad workers on both sides of the fence !
Now to answer the above quoted criticism levelled
at some amateurs. A project undertaken for enjoyment
in one's own time is bound to reflect this in countless
little ways. The finalised piece of home-made equip-
ment will carry some marks of the builder's own
personality, and not an inspector's rubber stamp applied
at the end of a production line. The amateur has no
time sheet to fill in, and if the fancy leads him to a little
extravagance — it is his own pocket he dips into. Fussy
concern for detail is no cause for condemnation, but
rather for envy. Many a professional must, on occa-
sion, wished he could have spent more time or used more
material on a given project. But in the commercial
world things are necessarily rather different. Ay,
there's the rub t
F. E. Bennett — Editor
THIS MONTH
CONSTRUCTIONAL PROIECTS
BOAT INTRUDER ALARM
TRANSISTOR CURVE TRACER
ELECTRONIC CYMBALS
P.E. ANALOGUE COMPUTER
FLUORESCENT
CAMPING LIGHT
SPECIAL SERIES
NUCLEONICS FOR THE
EXPERIMENTER— 7
TRANSISTOR AMPLIFIER
DESIGN— 4
GENERAL FEATURES
DENTOPHONICS
BEGINNERS
SEMICONDUCTOR BASICS 6
MULTIVIBRATOR
NEWS AND COMMENT
326
333
342
360
375
352
347
372
356
358
EDITORIAL
325
AUDIO FAIR PREVIEW
330
BOOK REVIEWS
346
BETTER SOUND
351
READOUT
376
Our June issue wilt be published on
Friday t May 17
All correspondence Intended for the Editor should be addressed to: The Editor, PRACTICAL ELECTRONICS, George Newnes Ltd., Tower
House, Southampton Street, London, W.C.2. Advertisement Offices: PRACTICAL ELECTRONICS, George Newnes Ltd., 15/17 Long Acre,
London, W.C.2. Phone: 01-836 4363. Telegrams: Newnes London. Subscription Rates including postage for one year, to any part of
the world, 36s. © George Newnes Ltd., 1 968. Copyright in all drawings, photographs and articles published In PRACTICAL ELECTRONICS
is specially reserved throughout the countries signatory to the Berne Convention and the U.S.A. Reproductions or imitations of any of
these are therefore expressly forbidden.
INTRUDER
FOR SMALL
CRAFT
-pHis article describes the construction of a simple low
cost alarm that will prove effective as a deterrent
to vandals or marauders visiting your yacht or motor-
boat.
Although primarily designed to prevent unlawful
entrance through boat doors and hatches, it may also be
employed as a burglar alarm for cars or as a domestic
sentinel. Current consumption on standby is exceed-
ingly low, in the order of microamps and the choice of a
silicon transistor in the first stage insures against
fortuitous switching of the relay through thermal
influences.
CIRCUIT DESCRIPTION
The circuit diagram for the alarm system is given in
Fig. 1. In essence the circuit consists of an npn
emitter follower TR1, the load of which is a 500 ohm
600 type relay RLA, followed by an astable pulse
generator (TR2, TR3) switching an alarm at a selected
frequency.
In the standby condition the transistor TR1 is held
off by the loop of closed microswitches which are fitted
to hatches and doors. It was found in practice that the
relay would not trip even for a loop resistance of
50 kilohms, so it can be seen that high contact resistance,
effected by alternative choice of contact plate switching
through poor connection, should not reduce the
efficiency of this alarm.
ACTIVATION OF ALARM
If the loop line is broken through forced entrance,
the small quiescent current through Rl is diverted to the
base of TR1 which switches on, so energising relay RLA.
The normally open contacts RLA1 close. This has the
initial effect of providing a latching potential to the
relay by way of R2 thus ensuring that any attempt to
cut off the alarm by closing doors or hatches and so
completing the loop is frustrated since the relay
armature is held in effect by its own contacts.
Any attempts by the marauder to rip out the loop
wires are equally ineffectual with this latching action.
ASTABLE MULTIVIBRATOR
The closed relay contact RLA1 also completes the
circuit for the complementary astable multivibrator
circuit composed of TR2 and TR3. Most readers are
326
probably familiar with the conventional multivibrator,
easily recognised by its crossed pair of feedback
capacitors. The circuit employed in this boat alarm
produces a similar output pulse, but it is very different
in its operation.
In the standby condition the electrolytic capacitors
C 1 and C2 are discharged, but with the closing of RLAI ,
CI charges through the point contact diode Dl and RLB
coil with a time constant appropriate to this series train.
Simultaneously C2 charges by way of RLB coil, VR1,
and R3 — with a relatively larger time constant.
Since the charging of C2 is exponential from zero, a
negative potential will appear at the base of the npn
silicon transistor TR2, proportional to the values of R3
and the frequency control potentiometer VR1. This
negative bias holds off TR2 and consequently TR3,
since no collector current is being passed to the base of
this transistor. With the charging of C2 the negative-
hold-off bias is removed and TR2 is switched into con-
duction with consequent bottoming of TR3.
This means that most of the supply volts now
appears across RLB so closing the normally open
contacts of RLB1. At this point the diode Dl is
reverse biased and does not allow the rapid discharge of
CI through TR3. This capacitor now acts as a
temporary supply to maintain the complementary pair
in conduction. With the discharge of CI and C2 by
way of the base-emitter junction of TR2, Dl, and VR1,
the circuit reverts to its original state, with relay
contacts opening prior to the next cycle of charging
events.
MARK-SPACE RATIO
Whilst the consumption of the operating unit is a
nominal 20mA, the current taken by the alarm audio
transducer will be very much greater. A degree of
power conservation can be achieved by adjusting VR1
for the smallest mark-to-space ratio.
This setting will of course, be a compromise between
an urgent alarm repetition rate, if this is required, and
the available capacity of the batteries employed.
If a bank of high power zinc-carbon dry cells, such
as Ever Ready HPl's are used with a car horn, the
mark-space potentiometer setting should be at its
lowest — although it must be stated that these cells
would be more suited to a large underdome bell as
an alarm.
COMPONENTS . .
Resistors
Rl 1 00k a
R2 33011
R3 270kQ
All 10%, | watt carbon
Capacitors
CI I00 M F elect. 15V
C2 8 M F elect. 15V
Potentiometer
VRI 10k ft horizontal preset
Transistors
TRI 2N2926 (Yellow)
TR2 2N2926 (Yellow)
TR3 OC7I
Diodes
Dl, D2
OA8I (2 off)
Switches
51 Bulgin s.p.s.t. key operated rotary snap
switch (Home Radio)
52 Push-to-break-single pole miniature push
button switch (Radios pares)
SW-SZ Alarm switches — miniature button
lever type (Bulgin) (Quantity
required)
Relays
RLA
RLB
9V 500 Q coil, I make light duty contacts
600 Type (Keyswitch)
9V 500 Q coil, I make heavy duty contacts
600 Type (Keyswitch)
Fig. I . Circuit diagram of the boot alarm
Connectors
PL I, SKI 8-way standard multi-pole connector
(plug, socket, cover shell and retainer,
Radios pares)
Miscellaneous
BY I 12V battery (see text)
XI Car horn (see text)
Diecast Box (S.T.C.) 8Jin x Sfin x 2^ in (Elec-
tron iques)
Miniature p.v.c. wire 7/40 (Radiospares)
}
§
5
)
j
I
I
17 18 19 20 l\ 22 23 24^25j,26
RLA coil
28 29 30
Fig. 2. The Veroboard
sub-assembly
fa) top view, showing
arrangement of com-
ponents
R ~
J c
I c
H C
G "5
F C
E C
c
C C
B G
■ ooooooooeo»oo oOoooo»oo • o i of <
>1~5"
^o
jj^o
3 Jo
looooooooeeooo ooooo(o)o»o«#o o(<
Boooeooooooooo eooo eooeeooo oft
ijoooooooooooooooooooooooooo(<
■ o oooooooooeoo oooo • o|oro o eTr^^^nl
Bo ooo ooo o • o o • o ooo o oto)o o o • o • • m
(b) underside view,
showing breaks in con-
ductor strips, and
soldered connections
1 2 3 4 5 6 7 8 9 10 fl 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
^* slfi *V^33^* %x '*
^V,
MOTE Retoy Srodwt
ucurcd to box with
3-4BA fixings \
Irtiu lotion
bushes
Fig. 4. Interior view of the main unit.* Relays and circuit
board have been moved from their normal positions to
clarify the wiring details
Obviously secondary type batteries, i.e. lead acid or
nickel cadmium will provide a much larger capacity,
and may be preferred. Of the latter kind, the DEAC
5M6 is suitable (two will be required).
VETO SWITCH
The key operated rotary snap switch SI is in shunt
with the alarm loop and is intended to be installed
outside the cabin or other protected enclosure. When
51 is closed the alarm is inoperative and hatches and
doors can be opened with impunity.
When the cabin is vacated and the door locked prior
to departing from the vessel, the keyswitch is turned and
the key pocketed, leaving the system set up. It follows
of course, that the siting of this switch should be such as
to make.it as inconspicuous as possible.
RESET SWITCH
If an intruder does set off the alarm the deactivation
procedure on return would be to close the veto switch SI
with the key, and then press the push-to-break switch
52 which will de-energise relay RL1, so breaking the
alarm contacts RLAI. Releasing this switch
immediately sets the system to standby again.
CONSTRUCTIONAL DETAILS
A suitable housing for the electronic assembly is an
S.T.C. diecast box slotted to take the Veroboard sub-
assembly (see diagrams and photograph).
Since this box is made of an aluminium alloy it is
essential to paint this with a waterproof metal primer
(as used on boats) to prevent corrosion. This should
be done after the unit is sealed so that the paint applied
forms a barrier to corrosive influences. Technical data
sheets on the choice of primers and paints applicable
may be obtained by writing for relevant data sheets to
British Paints Ltd., Little Ship Division, Northumber-
land House, 303-306 High Holborn, London, W.C.I.
Fig. 5. Relay mounting bracket
In the relay sub-assembly, drilling of all holes in the
mounting bracket should be done using the template
shown as a guide. Since the circuit consists entirely
of switching elements there is nothing particularly
critical in the construction.
The unit should be given a functional check prior to
boxing and particular care should be taken in making
the breaks in the copper strip of the Veroboard at the
extremes of the board, as one is sometimes inclined to do
this extremely fast with a spot fact cutter and leave
pieces of swarf to short adjacent strips.
LOOP CIRCUIT SWITCHES
It is recommended that linear action micros witches
be used in the loop circuit as "break-in" detectors.
Either the button or lever type microswitches may be
used as both types can be suitably recessed for doors and
hatches.
Perhaps a more economic system would be the
employment of stainless steel shims arranged to operate
as contact plates. Wiring to these plates would be by
way of eyelet tags, the assembly being both electrically
and mechanically joined by brads driven through eyelet
tags and shims to the wood backing. As this was not
tried in the prototype system it can only be a suggested
possible alternative.
Connection to all microswitch detectors should be by
miniature p.v.c. 7/40 wire. Although not as incon-
spicuous as thin enamelled wire, there is less likelihood
of abrasion producing false alarms through short
circuits if the loop wires are spliced in the run.
Since any attempt to cut wires will trigger the alarm,
concealment of these wires by channelling is not really
important. Any burglar who is au fait with alarm
systems would be deterred if he was made aware of some
protective guard against his intended pillaging; after all,
many motorists display stickers on their windows to the
effect that X's proprietary alarm system is installed
— which is a daunting first line deterrent.
ACOUSTIC TRANSDUCER
The audible alarm device suggested is a v.h.f. car
horn. However, since the contacts of relay RLB are
heavy duty, other types of alarm may be fitted, such as a
strident bell— this applies particularly if the system is
adopted for home or business protection.
For the larger vessel with its own power supplies,
existing hooters, marine horns, or loud hailers can be
connected in the external switch circuit.
If the system is used for car protection, horn and
headlights can be arranged in series with the RLB
contacts. This will necessitate the use of an extra pair of
contacts at the multi-pole connector PL1, SKI for load
sharing, as these contacts are only rated at 5 amps. -^
329
\ — MHf — ^
J U I
Baker "Major" loudspeaker
Garrard SL9S auto
transcription turntable
By M. A. Colwell
Now that stereophonic broadcasts are in full swing
in the U.K. (albeit of insufficient quantity and in
a limited number of areas) the manufacturers are
jumping on what is now an established bandwagon.
The trend to what is termed the "tuner amplifier" is
spreading to include stereo.
The problem re-emerges: What is the best unit to
buy? This is one question constantly being asked, and
it is almost impossible to answer in a few words,
because of the many and varied aspects which anyone
would look into— not least of these being the capital
cost.
Probably the best approach is to take advantage of
free entrance facilities offered to that popular event,
the Audio Festival and Fair (April 18 to 2 1 ). This year
the Hotel Russell, Russell Square, London. W.C.I,
will open its back doors once again to the hoards of
enthusiasts who diligently sort their way through the
hotel rooms looking (or should I say listening) for the
ultimate in sound reproduction.
Among a plethora of equipment, no doubt, the regular
visitor will find his pet subjects and the newcomer will
be baffled by what may appear to htm to be the old
game of hunt the thimble. How best can we help
him? First of all, decide before you go whether your
visit will be confined to certain types of equipment or a
general survey of the whole scene. Stamina could be
sucked dry if you attempt to take in every single item
and demonstration, so that by the time you reach the
fourth floor you will be glad to go down again.
If you are set on a particular branch of the audio
scene, get a catalogue— it will save quite a bit of shoe
leather. Browse through and make jottings of special
interests. See the equipment on the ground floor
booths; then after further jottings find your way to the
demonstration rooms of your choice. The catalogue
will help here again to locate these although, with a
little common sense and observation of the direction
arrows at strategic points, you should have no difficulty.
Now for the gear! The following is a preview of some
of the equipment to be seen. It is interesting to note,
during the current national prestige boosting campaign,
that imported products are generally more expensive
than the "home grown" varieties.
TUNER AMPLIFIERS
The "tuner amplifier" mentioned earlier is a term
applied in recent years to equipment combining radio
tuning and amplification. The addition of a loud-
speaker {or in the case of stereo, two loudspeakers) is
usually left to the choice of the user, since there is a
wide variety of types at different prices according to
one's requirements.
Typical examples are shown by the Sansui range.
The one illustrated here is the Model 2000 stereo
tuner amplifier which overcomes input matching
problems by using a field effect transistor at the front
end of the amplifier. Jnputs are provided for tape head,
pick-up, or tuner (internal) for mono or stereo listening.
Later this year the Sansui Model 3000A will be
available and offers a higher power output than the
current Model 3000. This is also in stereo. The
importers are Technical Ceramics Limited.
HOH^HHHBiHI
Sansui Model 2000 stereo
tuner amplifier
•
\
^
330
Arena stereo tuner amplifier type TISOOF with two HT2t speaker units
Arena of Denmark will be introducing their new stereo
tuner amplifier type TISOOF through Highgate
Acoustics. Modular construction has been used and ii
offers an output power of 6 watts per channel for input
sensitivities of 10// V for a.m. and 1/*V for f.m. The
picture shows the unit with two matching speakers
typeHT21.
In addition to their current range of tuner amplifiers,
the Trio Corporation of Japan are presenting a new
solid state amplifier, the TK.150E stereo, through their
agents B. H. Morris & Co. (Radio) Ltd., a subsidiary
of Lasky's Radio. The price compares modestly with
the Supreme I— a 64W per channel stereo amplifier,
employing separate bass, mid- and high-range amplifiers.
expected to retail at £280.
Armstrong will be showing their Series 400 and
Series 27 equipment which includes amplifiers, tuners,
and stereo decoders.
When selecting f.m. tuners, look for a.f.c. This
overcomes many drifting and fading problems often
caused by intervening obstructions between trans-
mitter and receiver, or varying atmospheric conditions.
Provisional information obtained from Rogers
Developments (Electronics) Ltd., reveals a new f.m.
tuner using an f.e.t, front end enabling it to handle
large signals without cross modulation, while at the
same time being suitable for areas of low signal strength.
A.F.C. is incorporated in this model. A multiplex
stereo decoder is available as an optional extra. This
"Ravensbourne 2" tuner has been designed to match
the "Ravensbourne" stereo amplifier.
SPEAKER UNITS
Many people have different ideas on what is the best
speaker. It is largely a matter of personal choice since
almost all manufacturers claim the best from their
units. Look for a specification with a high flux
density magnet and strong rigid frame if going for a
moving coil type. Of course, it must have an impe-
dance to match the amplifier. Excellent results are
obtained with the established Quad electrostatic unit.
Well known names such as Wharf edale, Whiteley,
Celestion, Goodmans, and so on, will no doubt attract
Shure M7SE-95G "Goord-o-Motie"
cartridge with suspension system
the usual audiences for comparative listening. Of
course, they all use different records, pick-ups, and
amplifiers, which may give slightly differing results.
So it is difficult to make direct comparisons, especially
when the rooms are packed with steaming bodies
under the floodlights. Perhaps you may be athletic
enough to dash from one room to another before the
memory of what was heard first has faded.
In between the aural bliss of Satchmo and the "1812",
take a look at the Titan Minor loudspeaker by Audio &
Design. This uses a titanium cone on beryllium
copper suspension. It is claimed to reproduce bass
more efficiently than conventional types for its size. It
is available housed in a cabinet I7iin x llin x 8{in.
Power handling capacitv is 15 watts from 40Hz to
22kHz. 4dB.
DISC EQUIPMENT
Ancillary equipment can be added ai various stages
as funds permit, but it is always worth making notes at
the Fair for future reference.
Pick-ups have seen some design changes in recent
years and it will be interesting to see what is new.
Tracking weight is frequenth a subject of much
confusion. Let it not be assumed automatically that
the lighter the stylus pressure, the better the performance.
Similarly with record wear, much depends on the
design of the pick-up arm and, even more, on the
true running of both turntable and disc.
Where these factors are near perfect, then one can
entertain the i ounce pressure, otherwise there is the
risk of groove jumping on less accurate turntables and
discs. Pick-up arms should be very free moving both
horizontally and vertically.
Of unusual design, the Shure M75E-95G "Gard-a-
Matic" Hi-Track cartridge, is designed specifically for
the new Garrard SL95 transcription turntable* (see
later). The performance is equivalent to that of the
M75E but with a retractile safety suspension system,
claimed to provide scratch- proof, bounce-proof opera-
tion where floor vibration is a problem. Shure also
Rogers "Ravensbourne 2" f.m. tuner
331
announce new models in the "economy" range of
cartridges. The M3IE and M32E have elliptical tipped
stylii for tracking at l-2gm and 2^-5gm respectively.
Audio & Design are introducing a stereo "induced
field" cartridge with an output of 0-9m V per cm/sec.
It uses an elliptical tipped stylus and is intended for
feeding into high impedance inputs.
Cosmocord have developed another version of the
stereo compatible cartridge announced last year. The
Acos GP91SC incorporates a mono crystal for mono or
stereo records. The stylus is suspended on a flexible
plastics arm so that it will track stereo grooves, while
reproducing a mono signal. It is available in three
versions with outputs of 200, 350, or 640mV at 1 '2crn/sec.
The Goldring Model GL75 transcription unit, with
"free field' 1 stereo magnetic cartridge, maintains the
tradition of their using variable speed motor units. The
new pick-up arm has a sliding counter balance to cali-
brate stylus pressure, and can be raised or lowered
hydraulically on to the disc by operating a simple lever.
Garrard equipment at a more modest price include the
AP75 single record player, Models SL95 and SL75
auto transcription turntables and the Model 3500 auto
turntable, with a low mass pick-up arm, and cue and
pause control.
The Model SL95 features "gimbal-type" pick-up arm
pivots; the arm has afromosa wood set into aluminium
for low frequency resonance damping. The record
platform can be pushed down out of the way for single
play operation.
Following some suggestions made to B.S.R. they
have now superseded the UA70 with a new Model
UA75, which uses a heavy cast alloy machined turn-
table.
TAPE RECORDERS
Probably the most interesting news in the tape
recording field is from Ferrograph. After 18 years of
pounding on their "Tape Deck" (which was originally
registered as a trade mark), with very little alteration
to the basic design, they have decided to up-date the
appearance and construction to the sleek squarish
model basic to the new Series 7.
The electronics are similarly up-dated to all. solid
state silicon devices, including f.e.t. input stages. The
machine can be used horizontally or vertically with easy
Ferrograph Series 7 stereo recorder
Goldring GL7S transcription unit with
tever operated pick-up arm
access to the electronic units. A time switch is in-
corporated for preset starting without the need for it
to be previously powered. Several other features are to
be found, based on principles in its forerunners. Pre-
record facilities for multi-play echo will be found on
stereo models, which are supplied with either half-
or quarter-track heads.
For another example of a professional studio tape
recorder, look out for the BTR4 by E.M.I. Its
complementary portable recorder the L4, with film
sync facilities is popular for field work among profes-
sionals and amateurs.
The latest Brenell deck, Mark 5 Series 3, will be on
show; features of this model include a self-compensating
braking system, and space for accommodating up to
four heads for mono or stereo.
ACCESSORIES
Microphones for mono or stereo will be in abundance,
including the MD409, and MD415 by Sennheiser
(through Audio Engineering), specially designed for
"pop" group vocalists. Both have an ti -feed back
properties and the bass response is tailored for close
microphone technique.
The same Company is also demonstrating a new pair
of stereo headphones, HD414, for those audiophiles
who want personal listening while the wife watches the
television.
The well known range of Shure microphones is to be
supplemented by the Unidyne IV series. Models 548
(mono) and 548s (stereo). These are designed for
professional applications and are fitted with Cannon
type connectors.
Finally, a word of advice. Don't arrive at the doors
without a ticket or you may not get in. Tickets can be
obtained free of charge through your local hi fi dealer
or from the organisers of the Audio Festival and Fair,
42 Manchester Street, London, W.l. (include a stamped
addressed envelope). ^X>
332
rE most useful test for a transistor is to plot its com-
plete range of input/output characteristics. Not
only will this show up the transistor limitations but a
great deal of useful information can be derived from a
study of the curves.
These characteristics can be produced by making
measurements point-by-point using meters to indicate
the value of currents flowing. However, this "static"
method is subject to a number of serious limitations,
the most important of which is the overheating and
possible destruction of the transistor when measure-
ments are attempted at the higher current end of its
characteristics.
A much better method is to allow the transistor to
reach its high current values for only a very short
period of time. This is called the "dynamic" method
and to use it a cathode-ray oscilloscope must be used
to display the transistor characteristics.
This article describes a unit which may be connected
to almost any conventional oscilloscope in order to
display the transistor characteristics. Single curves
can be shown and arrangements are included to permit
"families" of ten or more curves to be displayed.
METHOD OF TESTING
The basic technique is shown in Fig. 1 . Half sine
waves of voltage are applied to the collector of the
transistor from a mains transformer via a load resis-
tance Rl and rectifier Dl. A constant bias current is
fed to the transistor input through switch SI, either to
the base or the emitter depending upon whether
common-base or common-emitter curves are required.
A voltage proportional to the collector current (7c) is
developed across the load resistance Rl and applied to
the Y-plates of the oscilloscope. The collector voltage
Vch applied to the X-plates,
Thus as the voltage Vc varies from zero to the peak
of the half sine wave, so the current /c changes due to
t- le non-linear characteristics of the transistor The
fcLVc transistor characteristic is plotted on th£ c.r.o.
eeri. . ■■
Since the transistor is put through this cycle of applied
collector voltage change at a rate of 50 times per second
(actually 100 times if the reverse change of Vc is also
used as in Fig. 1) then a clear trace of this characteristic
is maintained on the face of the tube. This curve is,
of course, applicable to the particular bias current
chosen which depends on Vn and the value of bias
resistor R<q, To plot a series of such curves it is only
necessary to change the value of Ru in steps, allowing
one complete curve to be traced for each fixed value
of R\>.
With the simple arrangement of Fig. I it is possible to
plot hjVc curves for common-emitter or common-base
configurations by suitable settings of SI . Both pup and
iipn transistors can be tested by choosing the correct
polarity of half-sine wave obtained by the appropriate
setting of a reversing switch S2, connected to the
rectifier D I .
In order to convert this circuit into a practical arrange-
ment it is necessary to add a means of changing the
VoltQgtwovtfbtm
-*■
Tramistor
°sL«i
|§P switch rtvtraw
NPN wvtform pokwity
value of Rb between each curve traced in order that
multiple curves can be displayed. It will also be neces-
sary to include a cathode follower (or emitter follower)
between the X output of the circuit and the oscilloscope
in order to avoid loading the high impedance collector
circuit. This is particularly important when common
base curves are to be displayed. Several different
collector voltage and current ranges will be required to
accommodate all the transistors that are likely to be
tested.
PLOTTING FAMILIES OF CURVES
A convenient number of curves to produce a useful
"family" is about ten. These curves will be traced
one by one and in order to see them all together on the
oscilloscope screen it will be necessary to repeat them
fairly regularly (or alternatively a cathode-ray tube
could be used having a very long persistance phosphor
screen). What is required is a rapid single-pole ten-
way switch stepping on automatically and continuously
to repeat its sequence of ten positions. A Post Office
type uniselector switch meets this specification admir-
ably. For those not familiar with this device a brief
description will not be out of place. Refer to Fig. 2.
The uniselector switch is operated by applying a pulse
through the coil which pulls down an armature carrying
a claw to engage on the ratchet wheel, This wheel is
attached to the wiper arms of the switch; the fixed
contacts are arranged in a semi-circle around the switch
arm. Thus each applied pulse rotates the switch arm
by one position and engages with the next fixed contact.
Many versions of the uniselector are available and
can generally be adapted for our purpose. A number
of parallel banks of switch contacts are usually found
and three will be required for the Curve Tracer. A
standard type of driving coil is one requiring 50 volts
to initiate a switch operation. Other types may be
found and the driving voltage can be changed or coil
rewound to accommodate a different design. The one
used in the prototype had a 75 ohm coil.
FINAL CIRCUIT
The complete circuit is shown in Fig. 3. A stabilised
power supply is included which uses two 150V refer-
ence tubes VI and V2. This supplies the constant
voltage source for the base current determining net-
work, and also voltage supplies for the cathode fol-
lower V3 driving the X-plates of the oscilloscope.
A five-pole, two-way switch S8 enables either a single
curve to be traced or a family of characteristics dis-
played. (S is for a single sweep display; A is for
auto-repetition.) It is convenient to commence our
description of the curve tracer by considering switch
S8 to be in the "single" position.
The appropriate polarity of base current is selected
by switch S5 (generally negative for pnp and positive for
nptt transistors, although a reverse characteristic may
be required sometimes).
The reference voltage is applied to a potentiometer
network S6 which allows a selection of input currents
covering the range 10mA, 5mA, 2mA, 1mA, 500/* A, and
200/xA, depending on the switch position. Fine
control of input current for a single trace is provided by
potentiometer VR2, which can be calibrated 0-1, 0-2,
and 0-5 if desired, to correspond with the choice of
range available.
A meter is also included in the circuit to measure the
exact value of current supplied to the base. This has
current shunt resistors, wound to give full-scale
deflection of 10, 1, and 0-lmA. The current passing
Fig. 2. Side view of uniselector; the armature is at top
left above the coif
through the meter is direct current; a full-wave bridge
rectifier has been included in the circuit. This is to
avoid changing connections to the meter when the
polarity of the input voltage is reversed by S8. If
desired this bridge can be omitted and its place taken by
a reversing switch similar to that shown for S2.
The configuration of the transistor undergoing test is
selected by means of S4. This permits the current set
bv VR2 to be applied to the base or emitter depending
upon whether it is desired to display the grounded
emitter or grounded base characteristic.
The collector voltage is a rectified sine wave supplied
via D3 from the 50V secondary of a mains transformer.
The maximum amplitude of this sweep voltage is con-
trolled by the setting of potentiometer VR1. The
polarity of the sweep voltage is selected by S2 to suit
either pnp or npa transistors.
The sweep voltage is also applied via the cathode
follower V3 to the X-plate of the oscilloscope tube. A
preset adjustment VR3 is provided in V3 cathode
circuit to give zero adjustment.
The current axis voltage, representing the change in
collector voltage as the transistor collector potential is
swept through its range of values, is taken from across
a resistor, selected by S3, and fed to the Y-axis ter-
minal of the oscilloscope tube.
Six current ranges are provided for maximum
currents of approximately 5mA, 25mA, 500/* A,
250/tA, 100/M, and I0/*A, depending on the position of
S3. Resistor R7 is included to complete the circuit and
prevent a surge in current which would otherwise occur
each time S3 was moved to a new position.
When switch S8 is moved to the "auto" position, the
uniselector is brought into action. Instead of the
value of the input current being set by the position of
VR2, a set of resistors, R26 to R34, are sequentially
brought into circuit as the uniselector is stepped round
to each of its contact positions in turn.
A separate curve is displayed during the lime that
the uniselector is stationary and a particular resistance
334
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335
I'MlMiUmU^^iiM.Hi.M'li-H
PORTABLE TYPE
£9. 5. 0.
INPUT 230 240v. A.C. 50 60
OUTPUT VARIABLE 0-260v.
BRAND NEW
Keenest prices in the country.
All Types (and Spares) from
J to SO amp. from stock.
SHROUDED TYPE
I amp, £5. 10. 0. 2.5 amps,
£6. 15. 0. 4 amps, £9. 0. 0.
S amps, £9. 15. 0. 8 amps,
£14. 10. 0. 10 amps, £18. 10. 0.
12 amps. £21. 0. 0. 15 amps,
£25. 0. 0. 20 amps, £37. 0. 0.
37.5 amps, £72, 0. 0. 50 amps,
£92. 0. 0.
OPEN TYPE (Panel Mounting)
' F amp, £3. 10. 0. I amp, £5. 10. 0.
1\ amps, £6, 12. 6.
PORTABLE TYPE
1.5 amp. portable fitted rnetiil case,
voltmeter. lamp, switch, etc. £9.5.0.
Similar to above 2,5 amp. £1 1 .7.6.
100 WATT POWER RHEOSTATS (NEW) /ggt,
AVAILABLE IN THE FOLLOWING VALUES !$vlS>»
I ohm, 10 a.; 5 ohm, 4.7 a.; 10 ohm, 3 a.; *\„fe^J.'
25 ohm, 2 a. ; 50 ohm, 1 .4 a.; 100 ohm, I a.; " \jm)f.'
150 ohm, .7 a,; 500 ohm, .45 a.: 1,000 ohm,
280 mA; 1,500 ohm, 230 mA: 2,500 ohm, .2 a. Diameter
S^in. Shaft length s'"-. <•'»• A:i'". All at 27'6 each.
P. & P. 1/6.
50 WATT. 1/5/10/25/50; 1 00; 250 ,'500, 1 .000, 1,500.2,500
ohm, 21/-. P. & P. 1/6.
25 WATT. 1 0/ 25/50 / 1 00 ,250. 500 . 1 .000 1 , 500 : 2 , 500
ohm, 14/6- P. & P. 1/6. _
VENNER ELECTRIC TIME SWITCH
200-250 v. A.C. 20 amp. contacts twice on,
twice off, at any manually pre-set time.
Spring'reserve (in case of power cut) fully
tested £3/9/6. P. & P. 4/6. Or complete
in weatherproof metal case (illustrated)
£3/19/6, plus 4/6 P. & P. Can be supplied
with solar dial, on at dusk off at dawn.
Prices as above.
mm AIR BLOWER
Highly efficient blower unit fitted with ,
totally enclosed 200/250 v. A.C. 50 cycles. V
.'„ h.p. motor producing 2.&00 r.p.m.
Outlet 21 I)., used, but in first class con-
dition and tested . Pric e £3/15 .'-- P - & P . 7 6
230250V. A.C, SOLENOID
Heavy duty type, approx. 3 lbs. pull. Price: I
17/6 plus 2'6 P. & P. ^>k>
12 24V, D.C. SOLENOID
Appro x. 8 o z. push. Price fl,6 plus i 6 P. & P .
" PRECISION INTERVAL TIMER
From 0-30 seconds (repetitive). Jewelled
balanced movement. Lever re-set.
Operates 230V. A.C. 5 amp. c o Micro-
switch. New . Price 17,6 p l us 2.6 P . & P.
CONDENSER 4.000 mfd isv. 10.6 plus 1 6 p. & p
cTnstXnt^oijageTraIwformer" r-^
Input 185 250 v. A.C. Output 230 v A.C.
Capacity 250 watt. Attractive metal case.
Fitted red signal lamp. Rubber feet.
Weight 17 lb. Price £1 I / 10/0. P. & P. 15/ . '=^7^
PHOTO" ULTIPLIER. Type CV337" This super-
sedes type 93 1 A. Complete with special P.T.F.E. base
and divider network. 57/6 incl. P. & P.
RADIO
ALTIMETER
This precision instrument, built
to highest Ministry specification, is based on a 24 v. D.C.
LOW INERTIA Integrating Motor. The Motor, fitted
with gold brushes and drawing only 800 microamp at
24 v. D.C., drives two precision pots with platinum
wipers through close tolerance gear-trains, including
miniature slipping clutch, combined with two sub-
miniature pots for calibrating the electrical bridge
circuit. The 3 in. calibrated dial, with a number
aperture indicating one rev. per revolution of pointer
with maximum of 5 revs, gives an effective scale length
of approx. 30 in. Offered at fraction of Manufacturer's
price. 32/6. P. & P. 6/-.
LIGHT SENSITIVE SWITCH
f
Kit of parts, including ORPI2 Cad-
mium Sulphide Photocell, Relay.
Transistor and Circuit, etc., 6-12
volt D.C. op. price 25 - plus 2/6
P. & P. ORP 12 including circuit,
10/6 each, plus I/- P. & P.
A.C. MAINS MODEL Incorporates
Mains Transformer, Reetifier and special
relay with 3, 5 amp mains c/o contacts.
Price inc. circuit 47,6 plus 2/6 P. & P.
LIGHT SOURCE AND PHOTO
CELL MOUNTING!
Precision engineered
light source with focusible-l
lens assembly and ventilated
lamp housing, to take M8C bulb. Separate
photo cell mounting assembly for ORP. 12
or similar celt. Both units are single hole
fixing. Price per pair £2.15.0. P. & P. 3/6.
RESETTABLE HIGH SPEED
COUNTER. 4 figure, 1,000 ohm coil,
36 48 v. D.C. operation. £3/10/-. P. &
P. 1/6. 3 figure, 24 v. D.C. £1/12/6.
P, & P, 1/6.
DRY READ SWITCHES. New
special offer of Dry React Switches half
amp. Contact. Size li x i. 4 for 10/-
Fom P.. id.
MINIATURE UNISETEaoVswiTCH
3 banks of I I positions plus
homing bank. 40 ohm coil,
24-36 v. D.C. operation.
Testcd.22 6jjIus2/6P. & P.
COMPACT HEAVY DUTY 6v. D.C. RELAY
2 change over, 30 ohm coil. 7,6 each.
P. & P. I 6. 3 (or 20/-. Post paid.
"nIcKEL™ "cADmTum"" BATTERY
Sintered Cadmium Type 1-2 v, 7AH.
Size: height 3'. in., width 11 I ,1, in.
Weight: approx. 13 oz. Ex-R.A.F.
Tested. 12/6. P. & P. 2/6.
I/MP MULTI
RANGE METERS
New Model U50D Muki tester,
207000 OPV, mirror scaled with overload
protection. Ranges • d.c. volts: lOOmV,
0-5 v. 5 v., 250 v., 1,000 v.; a.c. volts:
2-5 v., 10 v., 50 v., 250 v., 1,000 v.: D.C.
current: 5 /-A, OS MA, 5 MA, SOMA.
250 MA, Complete with battery and test
probe. £7/5/0 post paid. Three other
models available from stock. Descriptive
leaflet on request.
THYRISTOR 400 piv, 5 amp,, 14 6 ™"
THYRISTOR 400 piv, 8 amp.. 28,6
~ 220~ 40 ~ A.C FANTlN IT™
2,300 r.p.m. 6" blade size. ^^«fc. v> <r
Smooth powerful motor. |"
All metal construction.
Continuously rated.
Individually tested.
Offered ac fraction of I
maker's price. £2.15,0,
— — '■J' —
SANGAMO WESTON
Dual range voltmeter. 5
and 100 v. D.C. FSD I m/a.
In carrying case with test
prods and leads, 32/6, P. &
P. 3/6.
A.C. CONTACTOR
2 make 2 break (or, 2
c/o.). 15 amp. contacts.
230/240V. A.C. operation.
Brand new. Price 22/6 plus
1 ,6 P. & P.
20 Amp LEVER MICRO
Brand new lever operated
Micro Switch. 20 amp A.C.
c/o contacts. Price 4/6 each
plus 16 P. & P. 5 for £
Post Paid.
SERVICE TRADING CO
All Mail Orders — Also Callers — Ample Parking Space
57 BRIDGMAN ROAD. LONDON, W.4 Phone 995 1560
SHOWROOM NOW OPEN CLOSED SATURDAY
336
Personal callers only
9 LITTLE NEWPORT ST.
LONDON, W.C.2. Tel. GER 0576
COLOUR TELEVISION
With particular reference to the
PAL SYSTEM
There are 157 diagrams and photographs and
83 illustrations in colour.
by G, N. Patchett
40/- Postage 1/-
MOOERN TAPE RECORDING AND
HI-FI, by K. Peters. 30/-. Postage I/-.
PAL COLOUR T.V., by Mullard. 12/6.
Postage I/-.
PRACTICAL WIRELESS SERVICE
MANUAL, Pub. Newnes. 25/-. Postage
ELECTRONIC COUNTING,
by Mullard. 27/6. Postage I/-.
BASIC THEORY & APPLICATION
OF TRANSISTORS, U.S. Dept. of Army.
12/-. Postage 1/-.
RADIO VALVE DATA, Sth ed. compiled
by "WW". 9/6. Postage I/-.
TRANSISTOR SUBSTITUTION
HANDBOOK, Pub. F.Sams. IS/-. Post-
age "/-•
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INSTRUMENT CASES AND CHASSIS
27 sizes and styles
OLSON ELECTRONICS Ltd.
Factory No. 8 5-7 LONG STREET
London, E.2 .Telephone 1 -739 2343
CIRCUIT DIAGRAM
Q
200V
IA
ikfi
■M50V
ToC.R.O. ToC.S.0
Common Y-Plott
Tsrminol
Fig. 3. The complete circuit of the curve tracer for connection to a d.c. oscilloscope
337
VEIP HAD JUST CL-KHfNT
is in the circuit. The uniselector is automatically
stepped on to the next position and a second curve is
displayed. The process then repeats and the whole
cycle repeats every 200ms. This is sufficiently rapid
to give the illusion of a stationary set of curves being
displayed on the screen simultaneously.
The uniselector is energised from the 40V secondary
winding of a mains transformer T3 via rectifier D4.
• • •
The primary of this transformer is connected to the
mains supply via one of the arms of the switch S8a.
A time-constant (C5, R8) is included in the primary
circuit in order to phase the application of an operating
pulse to the uniselector to correspond to the half cycle
when the collector sweep is inoperative.
COMPONENTS
It is appropriate to mention some of the components
used in the instrument. The majority of them are
easily obtained, but it may be necessary to select values
of some resistors by measurement of a batch of the
nearest preferred nominal types. Others will need to
be made up by combinations of suitable values, these
being indicated in the components list and in Table 1.
Resistors R35 and R36 are made from resistance wire
(eureka or nichrome) to give the required values to
indicate 10mA and 1mA f.s.d. on the meter. The
thinner the wire used, the shorter its length need be.
It can be wound on any insulating former to hand. If
the wire obtained is not insulated make sure that
adjacent turns do not touch; it is probably a good idea
to deposit molten wax on the finished article to keep
the wire firmly in place.
As an example, 38 s.w.g. eureka wire has a resistance
of 23-8 ohms per yard or I -5 inches measures one ohm.
Resistors
Rl l-5k<)
R2
R3
R4
R5
R6
R7
R8
R9
*RI0
Rll
>RI2
l-Skli
IkO
27k ii
68011
I2k£15%
22kti IW
lOkfi
5kn
Ikii
500 Q
RI3
RI4
RI5
*RI6
RI7
*RI8
*RI9
*R20
*R2l
*R22
R23
R24
loon
ion
ISkQ
30kQ
IBkO
5-4kn
6kD
9-6k«
3kQ
l2-2kQ
1-Bkfl
l-2kfi
*R25
*R26
*R27
R28
R29
R30
R3I
*R32
*R33
*R34
13-8ki2
1 35k Q
60kil
33ki>
27k Q.
ISkii
IOkO
6-4kn
3-8kQ
l-6k£l
R35, 36 {see text)
1A chassis or panel mounting fuseholder
All 10%, £ watt except R7, R8, R35 and R36
Resistors marked with an asterisk are not standard
preferred values and should be selected from nearest
preferred values, or made up from combination of
two resistors to give each required value. See
Table 1
Potentiometers
VRI 50kO linear carbon
VR2 lOkH linear wirewound
VR3 5000 linear wirewound
Capacitors
CI 16,/F elect. 450V C3
C2 IVr elect. 450V C4
I00 M F elect. 450V
100/iF elect. 450V
Transformers
Tl Mains transformer (Parmeko type P2752)
Pri.: +10, 0, 200, 220, 240V;
Sec. 1 : 200-0-200V 75mA; Sec. 2: 6-3V IA;
Sec. 3:6-3V2A; Sec. 4: 6-3V I A
(Sec. 3 and sec. 4 are not used in this circuit)
T2 Mains transformer (Douglas type MT I02AT)
Pri.:0, 210, 240V
Sec: 0, 19, 25, 33, 40, 50V 0-5A (Sec. 0-50V used for T2)
T3 Same as T2 but Sec. 0--40V used
Valves
VI Gas filled stabiliser type 1 50C2 V3 6LI8 triode
V2 Same as VI
Diodes
Dl BYZI2orSJ403
D2 BYZI2orSJ403
D3 G/3M
D4 GEX54I
D5-8 Meter bridge rectifier 1 0mA
Meter
Ml 0- 1 QOfiA moving coil
Fuse
FSI
Switches
51 Double- pole, on /off, toggle
52 Double-pole, changeover, toggle
53 2-pole, 6-way wafer (only I pole is used)
54 Double-pole, changeover, toggle
55 Single-pole, changeover, toggle
56 2-pole, 6-way wafer (only I pole is used)
57 Single-pole, 12-way wafer {only 3 ways are used)
or 4-pole, 3-way (only I pole is used)
SB 6- pole, 2- way (only 5 poles are used)
Uniselector switch
US I 3 or 4 banks, each 25 ways, coil resistance 75 Q
Terminals
X I , X2, X3 Screw terminals (3 off)
Plug and socket
PL I Mains plug, chassis mounting, type P73
Miscellaneous
Chassis lOin x 7in x 2in or made from aluminium
sheet I4in x Min 18 s.w.g.
Plywood or aluminium sheet for case I2in x Bin x
Sin internal dimensions
Clamps and insulation for C3 and C4 (2 off)
Valveholders, B7G (2 off); B8A (I off)
Tags boards, double, IB-way, 12-way, and 7- way
Tag strip, single, 5-way
Brackets for 1 8-way tag board
Pillars, 2 Jin long, for 12-way tag board
Grommets; 3-way terminal block
Seven knobs, nuts and bolts, wire
338
Table 1:
NON-STANDARD RESISTOR
COMBINATIONS
Required
Resistor
value Combination
RIO
SkO I0k£l - lOkii in parallel
RI2
SOOfl IkD - IkOin parallel
RI6
30k£> ISkfi I5kn in series
RI8
5-4ki> 2-7kii 2-7kH in series
RI9
6k Q I2kfl ■ 12k P. in parallel
R20
9-6k£2 6-8kO ; 27k fl in series
R2I
3kii 1-SkQ- l-5kft in series
R22
l2-2ki> I2k0 nominal selected by
measurement
R25
13-8k<> 56k Q 1 8kQ in parallel
R26
I35k0. 560kH ISOkO in parallel
R27
60kU l20kQ r I20kil in parallel
R32
6-4ki» 33kO 8-2kfi in parallel
R33
3-8kO 8-2kiJ 6-8kil in parallel
R34
l-6kil 5-6kii 2-2k Q in parallel
n
5ec50V
Fig, 4. Front pane! and chassis assembled. Hole sizes and
positions will depend on the components actually obtained,
but the wiring diagrams in Figs, S, 6, and 7 appear half scale
and give a reasonable guide to positions
I s r ff P* ■%
i I I I
,r]jr! Tr
I I
\*\W
R.
i|4m(3! [IZ"iHI ilOi i9i
Hv : VV L r J v
Ik. U_ ^tm ••• nil
NASA
w fill
1241 fcs
I, J L,J
.,
J
4N
i i
fR 1 '"(I" 1
L,J i-,J
I
r — ^
|R :R
ia! Izo!
rii rii O
jRiiR
|f9i H8 r
l,J LJ
I
i
Si
13)
R6 US(e T2 V3 USla ,TZ T3 TE 1 -%^' FS1
sec p,n6 ' y ' pii
Priftwiw Moins
Plug
COMMON
Fig. 5. Wiring the components on the front panel. The component group board Is tilted up to show connections, but
is in fact fitted to brockets on the front panel. This drawing appears approximately half scale
339
NOTE
Compontnt ftoord nounted
on Pillars abovt C3andC4
®
To VW
ToStc
ToSW (GoSf (O) To 05
Wiper v |-^ ^—^
for/'/l"/^/'//'/!/! /'/'/-//J /?/7/7/? /- 7/7 ~'/7/,
Hipir
taqs
,.
»SZb
, Wip*r
\ USI shown in schtmatk
form to clarify wiring
Fig. 6. Top side wiring of the chassis. Each dash on the uniselector represents an outlet tag; the wiper is at the right
hand end and coil connections underneath (not visible here). The uniselector is mounted on pillars above the chassis.
C3 and C4 are underneath the group board. This drawing appears half scale
i£3^
jBSfc
D2 C2 B3 m CI Rl H6
Fig. T. Underside wiring of the chassis. The group board is tilted to show the component wiring clearly
340
Do not allow the wire to become stretched or the
resistance will increase per unit length. The values of
resistance needed for R35 and R36 will depend on the
d.c. resistance of the meter coil. These can be cal-
culated from the formula:
Rs =
Ru x /m
Is — hi
where R$ is the shunt resistance required,
jRji is the meter resistance,
/s is the current scale required,
/m is the nominal current rating of the meter (in
this case 100/<A).
When making the calculation, resistances are in
ohms and currents in amperes, so allowance must be
made for the multiple and sub-multiple signs.
Capacitors CI and C2 are tubular types and usually
insulated. In any case the can of C2 must not be
connected to chassis. C3 and C4 are the kind that have
to be mounted vertically on the chassis, but here again
the can of C4 must not be connected to chassis. It
can be wrapped with plastics insulating tape.
The transformers have been selected as being readily
available types. TI has three 6-3 V windings but only
one is used for V3 heater. If desired, one of the other
6-3 V windings can be used to supply a panel bulb,
although this is not shown.
The diodes originally used were A El types SJ403 but
it may be easier to obtain the Mullard BYZI2, which
has a substantially higher current rating.
The wafer switches are pre-assembled types that can
be bought for a reasonable sum, but S8 may have to be a
slightly more expensive "Yaxley" or "Maka-s witch"
type.
The uniselector switch is obtainable at many surplus
stores. At least three banks are required and a 75 fi
coil. Check the action of this component before
buying to make sure that the wipers ride smoothly
through the arc of contacts. This can be done by
pressing the armature several times. No parts should
be damaged otherwise operation may be intermittent.
The uniselector has 25 ways; two series of 1 1 contacts
on each bank are paralleled.
FRONT PANEL
Front panel mounting position is given in Fig. 4 with
the wiring below it (Fig. 5). The wiring to S8 has been
abbreviated in the interests of clarity, but it should not
be difficult to ascertain the appropriate tags if wiring to
them is followed in alphabetical sequence, from a pre-
determined starting pole, in counter-clockwise fashion.
The "common" terminal on the front panel must
make either direct connection to the panel (if metallic),
or wired to a chassis connection.
Resistors for connection to S3 and S6 are mounted
on an 1 8-way group tag board, which is fitted to the
top of the front panel by right-angle brackets. If the
resistors are uppermost, minor alterations to their
values can be achieved in situ while the instrument is
operating.
CHASSIS CONSTRUCTION
Drilling details of the chassis are not given because
some adjustment may be necessary according to the
components acquired. However, the top and under-
side wiring diagrams of the prototype (Figs. 6 and 7) are
drawn to scale to give reasonable indication of the
positions of the components.
Transformer Tl is mounted so that the turret tags
project through the chassis for connection underneath.
Photograph of a family of IciYc curves displayed on an
oscilloscope
If there are "screen" tags on the transformers these must
be connected to chassis.
The main power supply components are mounted
on a group tag board under the chassis, while C3 and C4
are fitted (as mentioned previously) to clamps on the
chassis. It may prove to be helpful to make the holes
for these large enough so that they can project through
to about one inch below the chassis top.
A 12-way group board is mounted on pillars above
these two capacitors to take the resistors for USlb.
Here again, easy access is achieved for alteration of
component values.
Finally, before going on to the operation, a word of
warning: if it is necessary to make alterations while the
instrument is switched on, be careful where you put
your fingers and soldering iron. Components on the
front panel, as well as T2 and T3 carry exposed live
mains.
OPERATION
The curve tracer must be used in conjunction with a
directly coupled (d.c.) oscilloscope. The time base
must be capable of being switched out of circuit and a
d.c. amplifier substituted in its place. Not all oscillo-
scopes have this facility and it may be necessary to add
an amplifier to the design of the unit. It need only
have a modest gain of about a hundred times and quite
a small bandwidth and could derive its power from the
supply incorporated within the unit.
The type of display obtained is shown in the photo-
graph. The illuminated graticule shown in the photo-
graph was made from £in perspex placed immediately
in front of the oscilloscope screen. Edge lighting
through one edge of the perspex by means of a low
power bulb will light up the scribed scale lines. This
graticule was found useful in calibrating the curves
displayed on the screen.
The photograph shows the /c/ Vc characteristic of a
low gain pnp transistor having increasing values of
reverse. base bias. The ninth and tenth bias values
bring the transistor into its cut-off region and conse-
quently only a single straight line is traced for both
steps. -fa
341
So
eyj ^/wm^
THERE ARE two kinds of electronic music effects circuit :
one can be considered as self-contained and self-
generating; the other is dependent on a sound source from
a musical instrument.
Sounds made by real cymbals or drums can be modified
electronically to produce unusual effects. This is where
the Drummer's Whoosh Unit comes in; this will be based
on a modified version of the purely Electronic Cymbals
described in the present article.
The electronic cymbals unit uses the white noise
generator (described in January) and a power
supply (described in December) with a new filter circuit.
The circuits of the white noise generator and power
supply are reprinted in Fig. 1 so that the whole extent
of the circuit involved is realised from the outset.
The power supply is not shown in the photographs as
it was external to unit, but there is plenty of room to
incorporate it in the box if required. Alternatively,
the performer may prefer to use dry batteries, so making
the unit entirely self-contained and portable.
If required to be housed in the same box as the
Drummers Whoosh amplifier, this can still be done,
but we would recommend the constructor to exercise
some patience until next month's article appears. The
same box can house one white noise generator and
filter for both purposes, with modifications to suit the
Drummer's Whoosh.
With all these circuits it is necessary to add a power
amplifier and, since there is a wide variety of commercial
types available, the user should select one that will suit
the environment in which he is performing. Tone
controls are a desirable facility as will be seen later.
SWITCHED FILTER
One white noise generator will provide sufficient-
output to operate a set of cymbal effects circuits of
different pitches and qualities, giving a set of transis-
torised "cymbals" of relatively small size, and at
reasonable cost. The cymbals effect circuit is enclosed
in the dotted line box in Fig. la.
The 100 kilohm potentiometer VR1 controls the
level of the white noise signal fed to the filter circuit.
The white noise is filtered and deliberately "coloured"
by transformer Tl and capacitor C5, then passes by
way of C6 to the base of TR1. This transistor is
normally biased into non-conduction by a negative
supply applied through RIO. A 15V or 3V battery
will usually suffice here, and serves to prevent a hissing
noise between strokes.
342
10uF Xi* ME4I03
CYM6ALS FILTER
ATTACK* DEC*
r«t
C5
O-OCHuF
V
To^HS^
Ti
Fig. la. Complete circuit of the
cymbals effect unit
*LJ
O-Iuf
ISI50
15150^
i 1 *
S2o
Si/
«^<- Br
.08 _LC9 <^R9 ,
JW S50-0f_>K>
PF ~jjF ^
^ W ?Efftct?
jo output
I"
TR2
C4Z4or
ME4103
RIO
VW — E^
Puli« input _ WMA
POWER SUPPtY UNIT
Fig. lb. Modified
power unit to
supply negative
bias
In order to simulate a cymbal stroke, a positive pulse
must be applied to the circuit via C7, and must be of
sufficient magnitude to overcome the negative bias with
ease, and cause TR1 to conduct. To obtain a realistic
result, this calls for a pulse of at least 6 volts, and indeed
any voltage up to about 50 volts may be used.
A simple way to test the circuit would be to connect a
! megohm resistor from C7 to the negative supply
(common) line, and a Morse key or a push button
switch from this input to the 18V to 24V positive supply
line. A quick jab on the push button will charge up
C8 via diode pump D2 and D3. C8 will then discharge
by way of R8, R9, and TR1 .
R8 and C9 act as a filter to reduce "thump" effects.
As long as C8 holds sufficient charge, the potential
maintained at the base of TR2 will cause TR2 to
conduct, and to amplify the signal fed to its base via
C6. As C8 discharges, the output from TRl will die
away. This output is fed through a further filter-circuit
(T2 and CIO) to the effects output jack JK2.
It is worth mentioning that a l^V or a 3V battery
connected between chassis and the negative bias line
in this circuit will suffer negligible drain, and can be
wired in permanently without any need for an on/off
switch. A new leakproof battery would be likely to
last for a number of years (well beyond normal shelf
life), until corrosion sets in.
WwloRH
■_ Better results may be obtained from the circuit by
using an adjustable negative bias. The power supply
circuit in Fig. lb incorporates a negative bias supply
suitable for the purpose. Bias adjustment may be
used to control the decay time of the cymbal stroke.
ASSEMBLY AND TESTING
Prepare the printed circuit board according to the
design shown (Fig. 2) and assemble parts on it as shown
in Fig. 3. Fig. 2 shows the hole-spacing to suit a
TOS transistor encapsulation, and this spacing will suit
type C424. If type ME4103 is used, the hole spacing
may be made closer to suit the TO 1 8 leadout arrange-
ment of this transistor.
When assembly of the components on the cymbal-
effects circuit-board is complete, wire it up to a
white noise generator, d.c. power supply of 18V to 24V
and an audio amplifier or mixer unit. Temporarily
connect the positive supply line to the junction of
D2and D3. Switch on and adjust VRl and the controls
on the amplifier so that the sound of the white noise
generator comes from the loudspeaker as a loud hiss.
Disconnect the positive line from D2 and D3. The
sound should die away fairly rapidly. With some
transistors, the sound will fade to a very low level
without the need for a negative bias supply; others may
need the application of a negative base bias via RIO,
343
Fig. 2. Printed circuit pattern
for cymbals filter (full size)
TO S2a
Fig. 3. Layout of components on the printed circuit board
PULSE INPUT
TO JK1 & S1
*"■! ' TO JK1
-vtBIAS FROM VR1 WIPER © = TURRETUG
COMPONENTS
* • • •
Resistors
R7 1M£) R9 lOMil
R8 IMQ RIO 10MQ
All 10%, £ watt carbon
Potentiometer
VRI lOOkO log, carbon
Capacitors
C5 0-00 1 M F
C6
C7
C8
C9
OI^F
0-I^F
0-0 1 M F
CIO 00033/iF
All low voltage
> polyester or
paper
CYMBALS FILTER
Transformers
Tl, 2 Transistor transformers type
LT44 (2 off)
Transistor and Diodes
TR2 ME4I03 or
C424 (S.G.S. Fairchild)
D2andD3 IS 1 30 (2 off)
Jacks {with Plugs)
JK I , JK2 Standard ±in jack sockets
(2 off)
Switches
SJ Single pole push on, release off
push button
S2 Double pole on/off toggle switch
(S2a in low voltage line:
S2b mains input to power
unit if used)
Miscellaneous
Printed circuit board
Single core screened cable
Chassis I2in x 4in X 2yin
Knob
Component layout shown in Figs. 2 and 3
344
COMPONENTS
POWER SUPPLY UNIT
Resistors
Rll 47fl RI3 I-8Q
RI2 47 £2 RI4 I Mil IO%iW
All 5% 3W,-wirewound except RI4
Potentiometer
VR2 2Mfi linear carbon
Capacitors
CM 1,000/tF elect. 2SV
CI2 I.OOO^F elect. 25V
CI3 l t 0O0ftF elect. 25V
CI4 I ><.F polyester 160V
CIS 5<VF elect. 25V
CI6 I pF polyester 160V
CI7 0-l^iF polyester 160V
Transformer
T3 Mains transformer, charger
type. Pri. 240V mains; sec. 0-I7V I A
Transistors
TR3 XCI4I
TR4 AC 1 76
Diodes
D4 to DtO DDG00 (Lucas) (7 off) or IS 130
Switch
S2b (see under Cymbals Filter)
Miscellaneous
FSI Fuse 0-5A with holder
LP) Neon panel indicator with resistor
Printed circuit board 6in x 2£in
Heat sink for XCI4I
Knob
Component layout given in December 1967 issue
in order to achieve a quiet background in between
strokes, and a HV battery is usually quite sufficient.
If the positive line is quickly touched on to the junc-
tion of D2 and D3 a few times in succession, a sound
similar to a cymbal stroke may be heard, but may not
be very realistic at this stage, as adjustment of VR1
and the tone controls of your amplifier will have a
considerable effect on the output qualities.
VR1 must not be set too high, or the effect will result
in a continuous roaring or crackling sound. This is
because the white noise is fed to the base of TR 1 at a
high level to overcome the negative bias. Turn down
VR1 to a level somewhat below that at which the roar
occurs. If, now, the cymbal strokes tend to have a
somewhat crackly ending, VR1 must be set to an even
lower level to give a smooth finish to each stroke.
VARIATIONS
The circuit is not by any means restricted to the
component values given. By changing the values of
C5 and C10 the cymbals pitch may be altered; the use
of different transformers will give yet further ranges
of effects. A choke or other inductor could be used in
place of T2, and the output taken from the collector of.
TR1 by way of an 01/fF capacitor.
Changing the values of C7, C9, and R9 will affect
the "attack" and "decay" characteristics of the circuit,
WHITE NOISE GENERATOR
Resistors
Rl 4-7kS2 R4 2-7kii
R2 4-7kO R5 I5kil
R3 39kft R6 Ikfi
All 10%, i watt carbon
Capacitors
CI 25,iF elect. 25V
C2 10/iF elect. 25V
C3 lOO^Felect, 12V
C4 10^F elect. 25V
Transistor and Diode
TRI C424 (S.G.S. Fairchild) or ME40I3
D! Point contact diode, any noisy
type, such as sold for crystal
receivers
Miscellaneous
Printed circuit board 2in ■ 2in
(Bonanza Board)
Connecting pins and wire
Component layout given in January 1967 issue
Components for cymbals fitter given an
previous page
although the combine ji value of R8 and R9 should
not be reduced to a poi|t which would result in excessive
collector-dissipation iif TRI (rated about 200mW in
free air).
METHODS OF OPERATION
For manual operation, the simplest method is to
connect a 1 megohm resistor (R7) from C7 to the
negative (common) supply wire, and apply pulses to this
input from the 18V to 24V positive supply point by
use of a Morse key or a push button switch. The
final circuit shown in Fig. 1 performs the same function.
The circuit may also be operated electronically by
connecting C7 directly to an electronic switching
circuit (via JKl) such as a slow running multivibrator
(for automatic "repeat" effects); a ring counter (for
rhythm effects) or an electronic keying circuit. In all
these circuits the pulse may be supplied from the
collector of the switching transistor concerned. If
using the multivibrator described in the article on a
Simple Rhythmic Control Unit (February issue) JKl
would be connected to the collector of either TRI or
TR2 in that circuit.
The "Cymbals" circuit may be used very successfully
with an electronic rhythm machine or a rhythm genera-
tor. An adaptation of the circuit may be used for
beat group sound effects; this will be described next
month in the Drummer's Whoosh Unit.
345
S7ira
BEGINNER'S GUIDE TO ELECTRICITY
By Clement Brown
Published by George Newnes Limited
185 pages, 7£in. X Sin. Price 15s
Anyone starling a career or hobby in electronics
mighi be put off by the title of this book when
looking for an elementary guide. In order to under-
stand and appreciate the technicalities of even the most
simple of electronic circuits, one should have, or be able
to grasp, the fundamentals of basic electricity. Jt
comes at a time when more and more schools and
training colleges are giving courses in the subject, and
is therefore suitable for almost any beginner from
14 to 40 years of age.
It is written in an intelligently straightforward style
that will complement course lectures and lab. experi-
ments. Of necessity it is not by any means exhaustive
but will certainly cover in adequate terms the theory to
be found in advanced level G.C.E. and O.N.C. courses.
Electronics is not strictly introduced until Chapter 7,
and even then in only basic form.
Technical terms tend to baffle many beginners, but
here they will find explanations easily understood, and
related to everyday electrical appliances and electronic
circuits. Valve and transistor theory is included. The
relationship between theory and domestic and industrial
applications provides a suitable balance to a book that
could otherwise have been rather dry reading.
The final chapter gives some guidance for those
wishing to make a career in this fascinating activity.
M.A.C.
ABC's OF TRANSISTORS
By George B. Mann
1 12 pages. Price 20s
F.E.T. CIRCUITS
By Rufus P. Turner
160 pages. Price 25s
ABC's OF VACUUM TUBES
By Donald A. Smith
128 pages. Price 20s
BRIDGES AND OTHER NULL DEVICES
By Rufus P. Turner
143 pages. Price 26s
Published by W. Foulsham & Co. Ltd.
All 8|in x Si in
Another four titles
Foulsham Sams
expanding technology.
in the impressive catalogue of
educational primers in an
All four of the books present
their subjects with a minimum of mathematics apart
from the last title which sets out the necessary bridge
equations happily, without qualification. Treatment of
tjie subject matter is succinct and well illustrated and all
four volumes are recommended as beginning texts for
those anxious to be taught the rudiments of electronics.
ABC's of Transistors deals simply with the basic
physical and electronic features of these devices and
analyses their action in oscillators and amplifiers.
Practical servicing and testing procedure of these
circuits are also discussed.
F.E.T. Circuits is an excellent book for those readers
who like their electronics practical. From a brief
introductory chapter on structure and performance you
are launched into the whole gamut of circuit applica-
tions of this versatile high impedance device: trans-
mitters, receivers, test gear, control circuit, each one in
effect a potted constructional project as all component
and performance details are given.
ABC's of Vacuum Tubes. Dealing in the main with
the construction and action, both dynamic and passive,
of valves from the diode to the multigrid family.
Biasing and classes of operation are covered and the
final two chapters deal with miscellaneous and special
purpose valves. Altogether a painless introduction to
valve technology.
Bridges and Other Null Devices. Measurement is
fundamental to all sciences. In electronics the bridge
type circuit predominates in this application and this
book sets out to explore its various forms for specific
measurement purposes. From basic bridge circuit
theory the reader is introduced to most of the equipment
found in a test gear laboratory. Although the illustra-
tions are of American equipment, the principles and
measurement capabilities are universal.
G.G.
COLD CATHODE TUBES
By J. B. Dance, M.Sc.
Published by lliffe Books Ltd.
125 pages, 8fin x 5£in. Price 35s
In a world largely dominated by the semiconductor,
glass enveloped devices are becoming increasingly
rare. But one group of tubes seems to have gained a
new lease of life due, indeed, to the general expansion of
electronic techniques brought about by solid state
devices. For visual displays of data, or indication of
the operational condition of circuitry, there is no real
substitute for the cold cathode tube. This can be a
simple neon lamp (which may double as a voltage
regular), or a rather more complex numerical or
character indicator tube. The orange-red glow of neon
is the outward manifestation of electronic sophistry, as
we well know.
But the cold cathode tube family includes the well
known CM. tube for nuclear radiation detection,
stepping tubes for counting circuits, and other
important specialised types, besides.
The electronics enthusiast who is "genned up" on
solid state may be lacking in knowledge about cold
cathode tubes. He can now find the basic facts of gas
discharges and straightforward descriptions of those
tubes he is most likely to encounter in modern electronic
apparatus in this book. Some experiments with neon
diodes and trigger tubes are described and there are
many practical circuits which show typical applications
of the various devices. A good practical introduction
to the subject, with a minimum of maths.
D.D.R.
346
Transistor Amplifier
SUC1H
NEGATIVE
FEEDBACK
By A.Foord
Hi
'-.--.'-■ :J "' -•',;"-' ■
■V',-:-
Negative feedback occurs when a proportion of
the output voltage of an amplifier is fed back to
the input in such a way as to reduce the overall gain,
so that the gain with feedback is less than the gain
without feedback. Feedback can be used to:
(1) Give a predictable mid-band gain, the greater
the amount of feedback the less sensitive the
amplifier is to changes of transistor character-
istics.
(2) Increase bandwidth or to give a shaped fre-
quency response curve which depends almost
solely on the passive components forming the
feedback network, and does not depend on an
accurate knowledge of transistor parameters
(which may vary between one specimen and the
next of the same type).
(3) Increase or decrease input or output impedances;
by using different feedback arrangements it is
possible to obtain input or output impedances
higher (or lower) than those normally associated
with transistor stages. In particular it is possible
to arrange for a high input impedance and a
low output impedance, so that amplifier stages
can be cascaded without interaction.
(4) Reduce the distortion which normally occurs in
the final stages of an amplifier, where current
and voltage swings are highest.
BASIC PRINCIPLE
Any study of negative feedback begins with a func-
tional block diagram, Fig. 4.1.
The circuit has two signal paths: the forward path,
which is usually an amplifier and contains all the
active devices, is marked with its voltage gain A ; the
feedback path B which has a gain less than unity.
The bar above the symbol A indicates that there is a
phase reversal in the amplifier, while B represents the
fraction of the output voltage fed back to the input.
The phase reversal to obtain negative feedback
occurs in the amplifier; the arrows in the block diagram
reassure us that the feedback is in fact negative. In a
simple case this is obvious, but for more complicated
arrangements a check will ensure that we do not
accidentally use positive rather than negative feedback.
Take a simple example, Fig. 4.2. Without feedback
we require an input of OTV to the amplifier for an
output of — 10V. If negative feedback is added
making B equal to 01 times, 0-1V is still required at
the input of the amplifier itself to obtain an output of
-10V.
The input to the addition point needs to be 1*1 V, so
that when the — 1 *0V is added to the input we are left
with 0-1V to give an output of I0V. The overall gain
with feedback is now
G' =
-10
11
9-1 limes
The negative feedback has reduced the gain from its
open loop value of 100 times to a closed loop gain of
91 times, therefore the closed loop gain is approxi-
mately XjB times (1/5 = 10).
A more detailed examination will show that the
gain with feedback is approximately \jB provided the
closed loop gain is much less than the open loop gain,
Fig. 4.3.
Starting at the input to the amplifier (call this V)
then the output of the amplifier is A V, the voltage fed
back is A VB, and the input k V + A VB. Then the
overall gain with feedback is given by
C
Vo
Vi
AV
-1
AVB
1 4- AB 1 r _
A + B '
If B is much greater than If A (i.e. A is much greater
than \jB) then G = l/B.
«*>+
r fb
*-<?■
Fig. 4.1. Functional dia-
gram of an amplifier with
negative feedback path
fig. 4.2. A simple example
of negative feedback
3VB
V x *V + AVa*V{\+AB)
Fig. 4.3. Voltage relation-
ships between the amplifier
and the feedback circuit
347
1111 ."
^
A
FREQUENCY
FREQUENCY
Vv-
/^
SATISFACTORY
UNSATISFACTORY
Fig. 4.4. Gam and phase
characteristics which would
cause instability
Fig. 4.5. instability shown
by "ringing" cycles
Fig. 4.6, The practical
example of a high gain
amplifier with feedback re-
sistor and "anti -ringing"
capacitor C
Therefore, the ideal gain with feedback (C) is equal
to 1/B, if the gain without feedback (A) is much
greater than 1/5.
To confirm this, compare the results using the
accurate formula and the approximate formula; drop
the minus phase sign since we are interested in magni-
tudes rather than the phase reversal we know occurs in
the amplifier.
Actual closed loop gain
Ideal closed loop gain
C ■>
1 -f AB
r l
G =_
Calculation will show that, if the required gain with
feedback is one tenth of the gain without feedback,
then we do not need to use the accurate formula, since
errors in assuming G equal to 1 IB are small enough to
be discounted.
STABILITY
Having assumed that the design of the amplifier is
such that the feedback will always tend to reduce the
gain, but unfortunately this will not always be so, any
practical amplifier will contain reactive elements which
will introduce a phase shift in the signal as it passes
through the amplifier (quite apart from the 180 degree
mid-band phase shift required to obtain mid-band
negative feedback). The gain and phase characteristics
of the amplifier might appear as Fig. 4.4.
Above a certain frequency f, gain falls and an extra
phase lag is introduced. If we applied 100 per cent
negative feedback to an amplifier with this character-
istic, to give an overall gain of unity, the amplifier would
oscillate.
While there is still greater than unity voltage gain
around the loop, there is an extra 1 80 degrees of phase
shift to cause the feedback (which was negative below
/) to become positive at /'. The system would there-
fore oscillate at the frequency f.
Designing for stability is complicated when a con-
siderable amount of feedback is applied, instability
in a feedback amplifier is shown by a peak in the
frequency response curve and ringing on a square
wave signal (see Fig. 4.5).
Feedback over one or two stages is normally safe,
although later on, when considering the use of 100 per
cent feedback to raise input impedance, a non-mathe-
matical approach will be applied to the stability
problem. For most purposes, it is in order to see that
the frequency response curve does not have a peak of
more than a couple of decibels in it, and that the square
wave response is satisfactory, i.e. free from ringing
effects.
The photographs show results obtained with a high
gain amplifier, this had a gain of 1,000 times (60dB)
without feedback, and a gain of 10 times (20dB) with
feedback (see Fig. 4.6).
Photo A shows the leading edge of the I kHz square
wave input ; photo B shows the ringing on the output
waveform without the capacitor C, and this was con-
sidered unsatisfactory. The capacitor was adjusted in
value to obtain the acceptable response of photo C.
Since for clarity the photographs only show the leading
edge of the square wave, the time scale was extended to
show the leading edge more clearly. The capacitor
was increased to reduce the bandwidth to 20kHz
which increased the rise time to that shown in photo D.
Feedback around one stage only is called local feed-
back, and since only the common emitter stage pro-
vides a phase reversal of its output signal with respect
to its input, it follows that local feedback can only
be applied around the common emitter stage.
There are two basic ways of applying feedback to
the common emitter stage; one arrangement is con-
sidered next, and the other is dealt with later, in the
section on virtual earth amplifiers.
SERIES LOCAL FEEDBACK
Referring to Fig. 4.7, the resistor Rv. in series with
the emitter accounts for the applied feedback, this
resistor enables a feedback voltage Vt proportional to
load current, to be fed back in series with the input
voltage V\. The base-emitter voltage of the transistor
is reduced by the feedback so that Kn E is less than V\.
If Rf. is small and of the same order of value as the
internal emitter impedance rn (say 100 ohms or so),
then the amount of feedback is small. Distortion is
slightly reduced and bandwidth is increased very
slightly, at the expense of a small decrease in gain.
If Re is large then the gain is given by
G - n ~ m
The input impedance is given by
Zi = htcRiz
348
INCREASING * E
FREQUENCY Hz
Fig. 4.t. Strict local Fig. 4.8. The effect of Rf
feedback by the unby- on gain and frequency
passed emitter resistor response
Fig, 4.9. Emitter follower output to prevent undue
loading on the amplifier stage
In practice for a single stage amplifier biased in the
normal way with a divider chain on the base, this
increase In input impedance is masked to some extent
by the shunting effect of the chain. The effect of Re
on gain and frequency response is as shown in Fig. 4.8.
To avoid loading J?l and to maintain a high gain
without feedback, the output can be taken via an
emitter follower, a practical circuit is shown in Fig. 4.9.
Since the transistor is used in common emitter we
must work out approximately the bandwidth we would
expect. For TR 1 the collector current is of the order of
0-5mA. Suppose the transistor current gain is typically
50 at 0'5mA. The 3dB down point in common emitter
is given by
1,000
J Ate
50
/ = 20kHz.
One would expect the response to roll off somewhere
at this frequency, the exact point depending on Are and
ft for the particular specimen of transistor. Since
TR2 acts as an emitter follower the overall frequency
response is limited by TR1 since an emitter follower
has a 'frequency response far better than that of a
common emitter stage.
Photo A. Leading edge of the I kHz square wave
Photo C. Ringing is brought down to an acceptable level
by selection of a parallel capacitor across the feedback
resistor
Photo 8. Ringing caused by non-selective feedback
Photo D.
rise time
Larger value of capacitance increases the
349
The results without feedback (C2 connected) and
with feedback are:
Gain without feedback
Bandwidth
Input impedance
Output impedance
Maximum output
310 times 50dB
30kHz
IkO
300 Q
1-5V r.m.s. no load
500mV r.m.s. into lkH
The frequency response was measured under no load
conditions at lOOmV r.m.s. Up to 50kHz or so, the
amplifier will provide 500mV r.m.s. into 1 kilohm, but
above this frequency the emitter follower current gain
starts to drop and the waveform distorts, so that
500mV would only be obtained without distortion into
a load greater than 1 kilohm.
The gain without feedback appears high until we
remember that the collector load is 27 kilohms rather
than the 1 kilohm or so we would expect for another
common emitter stage and a high gain transistor is
being used.
Gain with feedback — = 10 times = 20dB
Bandwidth
Input impedance
Output impedance
Maximum output
27
2-7"
68kHz
7k a
300fi
500mV r.m.s. into
(up to 50kHz)
IkO
The actual measured gain was 19*5dB, which is
probably an error in measurement or tolerances on the
collector and emitter resistors. Since the open loop
gain is 30 times the closed loop gain, one might expect
the gain of 20dB to be independent of variations in
characteristics between one OC75 and the next,
although the bandwidth might alter slightly.
Although the gain has been reduced by a factor of
30 times, bandwidth has only increased twice. Series
local feedback is often used inside another overall
feedback loop, where a predictable stage gain is
required rather than an unpredictable (though higher)
gain.
With an input impedance of 7 kilohms and an output
impedance of 300 ohms, these amplifiers can be cascaded
GAIHdB
A1 AZ 40
A1 OR A2 20
12<ffi/0CTAVE
6dB/0CTAVE
&
"\
FHE0UEMCY
M
Fig. 4.(0. Combining
two identical amplifiers
Fig, 4.11. The response of
each amplifier is added
to give overall response
^***y R R R **\^ R
- GAiM>YWYSAAfWS- t c *$ > ~t' w t~
T T T T J -L
Fig, 4.12. Equivalent cir-
cuit of a transistor looks
like that of a transmission
line at high frequencies
Fig. 4.13. A single CR
conversion of Fig. 4.12
without interaction. Bandwidth is also extended at
the low frequency end, but since this is within our
control (coupling and decoupling capacitors) the main
benefit of this type of negative feedback is the pre-
dictability of mid-band gain rather than the small
extension of bandwidth.
TRANSFER FUNCTIONS
The amplifier can be represented as a block, so that
two amplifiers in series could be represented by adding
the two separate gains in decibels (see Fig. 4.10).
A,
■= 10 times
20dB
A, A.,
= 100 times
A ?
-= 10 times ■
20dB
= 40dB
Working on the frequency response curve and adding
decibels this would result in the response shown in
Fig. 4.11.
20
IS
10
At
AZ
1
-3
3
3.
m_
i SLOPE 6d»/ OCTAVE
IZOaa/DECADEJ «
35
30
l 25
\ 20
to
>*
AWROXIMAI
E CUR
VE
!■"!
B
»■
"* m
^-^S^
"^J
^
i
h-^
ACCURATE CURVE —
>s
_
$!
s
0-1 1 t lOf
Kg
res
ret
FREQ
. 4.14. Appro xi'm
pome, then der
ponse (solid line)
UEHCT
oting t
iving t
he freqt
he ace
iency
urate F
t 2 5 10 20 50 U
FREQUENCY (kHz)
fg. 4. 1 5. Summing the response of two amplifiers in cascade
n
350
Where each amplifier was 3dB down (at /), the
response is now 6dB down (for two identical amplifiers),
and the new 3dB down point is lower down at/i, as one
would expect. The slope of the curve for a single
amplifier is approximately 6dB per octave, and for
two amplifiers in series this will be 12dB per octave.
In the equivalent circuit of a transistor (Fig. 4.12) it
appears as a transmission line for high frequencies, but
as a first approximation it can be considered as a
single CR network, Fig. 4.13.
Taking the CR network or single time constant on
its own, at low frequencies C has a high impedance
and Vq = V. At a frequency when C has a reactive
impedance equal to R, V Q is 3dB down with respect to
V, and continues to fall at 6dB per octave (20dB per
decade) with increasing frequency, as in Fig. 4.14.
The solid line curve is the accurate frequency res-
ponse, while the dotted line is the straight line approxi-
mation. The point / where the impedance of the
capacitor is equal to the resistor is called the "turnover"
or break point. The maximum error between the
accurate and straight line approximation is 3dB which
occurs at the break point. In practice the approximate
curve is drawn; /is 3dB down, 0-5/ and 2 /are ldB
below the approximate curve; the accurate curve is
drawn from this information.
For two amplifiers in cascade the procedure just
outlined is shown in Fig. 4.15. The bandwidth of the
two amplifiers in series is almost identical, but the
ultimate slope is now 12dB per octave rather than the
6dB per octave for a single common emitter stage.
RELATION OF RISE TIME AND
BANDWIDTH
A square wave can be considered as the sum of a
number of harmonically related sine waves; these
include a fundamental sine wave at the basic repetition
frequency and frequencies of three, five, seven times,
and so on (odd harmonics of the basic frequency).
If a square wave of 1kHz is fed into an amplifier with
a sharp cut off at l-5kHz all the harmonics are filtered
out, leaving only the 1kHz fundamental, Fig. 4.16.
If the response of the amplifier is extended to 20kHz
the output would consist of the fundamental and
harmonics up to 19kHz. Harmonics at 21kHz,
I\I -
INPUT OUTWIT
Fig. 4.1 6. * A square wave signal can be filtered to
give the fundamental frequency only
_TLP-
INPUT r OUTPUT »
1kHz 1kHz
Fig. 4.17. Increase in the rise time of the square
wave by loss of harmonics
23kHz upwards would be attenuated according to the
roll-off of the amplifier response curve. The square
wave would hardly be degraded at all, since the ampli-
tudes of these harmonics (relative to the fundamental)
are small. The loss in harmonics increases the rise
time of the square wave, Fig. 4.17.
To determine the bandwidth of an amplifier we would
feed in a square wave with a rise time better than we
would expect the amplifier to handle, and measure the
degradation on the output.
Suppose our square wave had a rise time of 5/ts and
after passing through the amplifier this was degraded
to 25/fs, then our amplifier has a rise time of \/(25 3 - 5 2 )
or 24-5/ts and its bandwidth is given by:
/-
0-35
_0-35
rise time 24-5
x 10« = 143kHz
This method is only an approximate means of deter-
mining bandwidth, it would tell us if our amplifier had
a bandwidth of 20kHz- or 10kHz, but we could not rely
on discriminating between bandwidths of 20kHz and
17kHz.
However the edges of the square wave do represent
the type of signals present in a transient, Which simple
sinewave testing cannot do, so that we can see immedi-
ately any instability or excessive overshoot or ringing
in the amplifier. The disadvantages are that we do
need a square wave of good rise time, and an oscillo-
scope capable of showing it.
Next month: Negative feedback applied to prac-
tical circuits.
BETTER SOUND
The BBC announces that four programmes in a new
series "Better Sound" will be broadcast on Fridays
at 7.00-7.30 p.m. in Study Session, Radio 3 from May 3
to 24. Listeners will be invited to send questions of general
interest, or requests for more information on particular
topics covered in the series and these will be dealt with in
two extra programmes which will follow the repeat of the
series later in the year.
The series will be repeated on Radio 4 on Saturday
mornings at 11. 00-1 1 .30 a.m. from August 17 to September
14. There will be no programme on August 31 (Bank
Holiday weekend), but there will be two additional pro-
grammes on Saturdays, September 21 and 28.
Each programme will focus attention on one area of this
wide field. A number of topics (e.g. microphones, loud-
speakers, stereo) will therefore be treated in more than one
programme. Advice on particular makes cannot be given
and the construction and repair of equipment will not be
dealt with.
Programme 1 : Transmission and reception of radio,
including stereophonic broadcasting. Explanation of
AM and FM, etc.
Programme 2: The nature of sound, and room
acoustics, with demonstrations of the effect of different
placings of microphones and loudspeakers.
Programme 3: The reproduction of music in mono
and stereo; hi fi equipment.
Programme 4 : Tape-recording for the amateur.
The diagrams in the Study Notes (BBC Publications,
2/6 plus 5d postage) will be helpful in following the broad-
casts and the explanations in the text of the basic principles
of the transmission, recording and reproduction of sound
in mono and stereo will be useful for reference, particularly
for the less knowledgeable listener.
351
1?^^.
«f
ERIMENTER
*£
• By M.L. Michaelis M.A
/^RADIOACTIVITY MEASUREMENT; STRACE RADIATION METER
Previous articles in this series have discussed nuclear
radiation, atomic structure, and the practical
applications of nucleonic measurements; measuring
methods and various kinds of detectors have been
considered in a general Way. A distinction lias been
made between activity measurements and energy
measurements, and electronic methods for sorting
electrical pulses sfrom a spectroscopic, i.e. energy-
distinguishing, nuclear radiation detector explained.
Mow theiPoint is reached where wc have sequences of
pulses, ready for activity determination, i.e. for counting
the numbers arriving per unit time, corresponding to the
numbers of radioactive atoms disintegrating per unit time!
This counting process is the function of the actual radiation
meter unit in any nucleonic equipment. This month, we
will discuss the basic requirements and electronic circuit
techniques which are involved. It is quite immaterial
whether the pulses originate from a non-spectroscopic
detector like a G.M. counter, or from a spectroscopic
detector such as a scintillation detector with kick-sorter
amplifier.
In the former case, the mean pulse frequencies may
correspond to the gross activity of a mixture of different
kinds of radioactive atoms, whereas in the latter case, the
activity of a particular species of radioactive atoms can be
observed selectively, to the exclusion of others which may
be; present at the same time in the radioactive sample.
However, the principles of making activity measurements,
and the structure of the radiation meter used for the
purpose, are the same in both cases.
ACTIVITY AND DETECTION EFFICIENCY
The activity of a radioactive sample is the number of
atoms disintegrating in it in unit time, irrespective of the
type of disintegration or the energy of the emitted nuclear
radiation. We have already seen {in Part 3) that the unit
of activity is the curie (Ci), corresponding to 2*2 x 18 12
distintegraiing atoms per minute. This is the activity of
I gram of pure radium, by definition. Convenient prac-
tical units for amateur measurements are the pko-curie
(pCi), corresponding to 2-2 disintegrating atoms per
minute in the given sample, and the nano-curie (nCi).
corresponding to 2,200 distintegraiing atoms per minute
in the given sample.
ft is customary to take one minute as the time unit for
radiation meters, so that their essential function is to
determine the pulse counts per minute. The abbreviation
c.pm. is conventionally used for "counts per minute"
STRACE
RADIATION
METER
352
It is not possible to calibrate a radiation meter directly
in pCi or nCi, but only in c.p.m. This is because the
ratio of c.p.m. to pCi depends on the numerical detection
efficiency of the radiation detector employed. The ratio
is 2-2 only if every disintegrating atom in the radioactive
sample produces an electrical response pulse in the de-
tector. This is rarely the case in practice; a greater or
smaller proportion of the radiations will miss the detector,
so that the ratio c.p.m. /pCi is practically always con-
siderably less than 22. Of course, it is the aim of any
detector and sample arrangement to achieve as high a
numerical detection efficiency as possible. This is also
referred to as the geometry factor.
TWO EXAMPLES
Two examples will make this point clear.
In the first case, consider a radioactive sample lying on
a large flat radiation detector, i.e. G.M. counter. The
nuclear radiations may be emitted in any direction by
chance. Thus, on the average one half of them will fly
upwards or obliquely upwards, and miss the detector.
The other half will travel downwards or obliquely down-
wards, and enter the detector to produce a pulse. The
ratio c.p.m. /pCi would be M in this case.
In the second case, consider the sodium iodide crystal
of our scintillation detector {see Part 5), with the radio-
active sample placed at the bottom of the axial sample
well. Nuclear radiation emitted in almost any direction
will then strike the crystal, so that we would expect very
nearly the ideal value of 2-2 for the ratio c.p.m. /pCi.
In practice, we actually find values considerably smaller
than 1*1 and 2*2 for the respective cases, because two
further factors reduce the detection efficiency. Firstly,
some quanta of radiation may be absorbed within the
sample, or other insensitive material, before reaching the
sensitive detector region. Secondly, some quanta may
pass straight through the detector without getting absorbed
to produce a pulse. Thus the ratio c.p.m./pCi is only
about 0-1 for a liquid sample in the Mullard MX124/01
G.M. counter tube specified for our equipment (see
Part 4). The scintillation detector possesses a considerably
greater detection efficiency, under some conditions
approaching closely to the ideal value of 2-2 for the ratio
C.p.m./pCi.
RADIOACTIVE DECAY
Since the activity of a given radioactive sample is a
statement of the number of atoms disintegrating per unit
time in that sample, this activity must necessarily diminish
with the progress of time, because the number of atoms
left over is continuously decreasing. For any given
species of radioactive atoms, the activity is strictly pro-
portional to the number of atoms of that species which
are present in the sample, i.e. the rate of decay is directly
proportional to the amount present.
This is the basic characteristic of any exponential
process (the rate of fall of the voltage across a capacitor
discharging through a resistor is always proportional to
the actual voltage left across the capacitor at the instant
considered, or the rate of growth of a sum of money on
compound interest is at all times proportional to the
accumulated capital). Thus the activity of a simple
radioactive sample decreases exponentially with time.
This is a very important principle, known as the radio-
active decay law.
Different species of radioactive atoms decay at different
rates, which are specifically characteristic of the respective
species, just as different capacitor/resistor combinations
discharge at different rates according to the produce of
capacitance and resistance (time constant) of the circuit.
DECAY HALF-LIFE
For radioactive samples, we specify a decay half-life.
This is the time taken for one half of a large initial number
of atoms to disintegrate. If we wait a further equal period
of time, one half of the remainder will have disintegrated,
i.e. the number of atoms still left over is halved during
each successive half-life period. The process theoretically
never goes to completion. The smaller the number left
over becomes, the greater the random departures from
One of the rotemeter
modules of the
STRACE Radiation Meter
smooth exponential decay. Ultimately, when only one
atom is left over, it is inherently impossible to predict how
long it wilt continue to remain intact.
A similar indeterminacy prevails already at the outset,
when we had a very large number of atoms. If we were
to single out any particular atom for close observation,
there is no way of predicting, in which successive half-life
period it will meet its fate. This is subject to pure chance.
Thus whilst we can be pretty sure that almost exactly one
half of a large number of atoms will disintegrate in a
half-life period, we are unable to determine in advance
which particular atoms will belong to the decaying half.
STATISTICAL FLUCTUATIONS
The inherent unpredictability of the lifetime of any
single radioactive atom introduces random fluctuations in
the predictable mean behaviour of a large number of
similar atoms. If the smooth exponential decay law
would ideally demand that n atoms should disintegrate in
a given sample within a certain time of observation, then
the actual number of atoms observed to decay within that
time will in all probability differ from n. It may be
smaller or larger. If we repeat the experiment numerous
times under identical conditions, the average of all observa-
tions will approach ever more closely to n. Regarding the
discrepancies of individual results, we will find that these
average to ± \'n. This is called the mean uncertainty of
the count n.
As far as practical measurements are concerned, this
means that if we want our activity reading to be reliable
to within 1 part in n, we must count at least « a pulses
before we stop the counter and divide by the total time
taken. Otherwise random fluctuations will exceed our
tolerance limit and the readings are meaningless to the
envisaged accuracy.
It is common practice to specify four accuracy classes,
namely 1, 5, 10, and 20 per cent. These correspond to
desired reliabilities of 1 part in 100, 20, 10 and 5, so that
we must respectively count at least 10,000, 400, 100 or
25 pulses.
Note carefully that it is solely the total pulse count which
determines the statistical accuracy, quite irrespective of the
time taken for clocking-up this count. The radiation
meter must simply be left running until the required
number of pulses have arrived, and if this takes a very
long time in the case of low activities, the circuits must be
designed with adequate long-term stability.
RADIATION METER TIMING
The relationships explained in the previous section
dominate the design of practical radiation meters. In the
case of digital counting, there are few basic problems as
far as long-term stability is concerned. Professional
equipment often adopts count timing here. In other
353
PULSE INPUTS FROM BftOIATtON DETECTORS
Fig, 7.1, STRACE RADIATION METER: Circuit diagram of the ratemeter module
words, the time taken to achieve a predetermined count
is measured. Suppose we desire a statistical accuracy of
1 per cent. The clock will then be zeroed and the counter
set to 10,000. The clock is then set running forwards
and the counter backwards. When the counter reaches
zero, it stops the clock automatically.
In the case of analogue counting, more special con-
siderations are required. We remember that analogue
counting establishes the activity reading as the voltage
developed across a capacitor. Each pulse pumps a
definite small electric charge into the capacitor, whilst the
capacitor at the same time discharges through a precision
resistor. The resulting voltage across the capacitor is
directly proportional to the rate of arrival of the pulses.
This voltage will fluctuate in a random manner, due to the
random fluctuations of the pulse rate. The meter reading
thus fluctuates over a certain range of the scale, instead
of being steady.
RATEMETER TIME-CONSTANT
Consider the lowest range of the ratemeter in our
STRACE equipment, which is 100 c.p.m. for full-scale
deflection. The design figure is the 5 per cent statistical
accuracy class, which calls for 400 pulses in the "counting
time". These take four minutes to arrive at 100 c.p.m.,
so that the product of the integrating capacitor value
(pF) and its discharge resistor (megohms) should be 240
seconds.
If the value of the capacitor is kept constant, but the
value of the discharge resistor halved, then a given pulse
rate will produce only half as great a meter deflection.
The full-scale deflection c.p.m. value is thus doubled. But
the statistical accuracy is unchanged, because although the
time constant has been halved, the rate of arrival of the
pulses for full-scale deflection has been doubled, so that
the same number of pulses arrive within the time-constant
period.
In general, this leads to a simple rule. The various
desired c.p.m. ranges are obtained by switching corre-
sponding different discharge resistors across the same
integrating capacitor, whereby the same statistical accuracy
is then obtained on all ranges. This is most fortunate,
since only one capacitor is thus required. The capacitor
must be of immaculate quality, above all, it must have
very low leakage and excellent long-term capacitance
stability, so that it is rather expensive. Precision resistors
are much cheaper, and only these are required in quantity
according to the desired number of ranges.
STRACE RATEMETER MODULE
Fig. 7.1 shows the complete circuit of the ratemeter
module for the STRACE radiation meter unit.*
The components within the broken-line rectangle are
accommodated on a 4in x 6in printed circuit board.
Layout is in no way critical.
Almost any silicon npn transistors are suitable for
TR2, 7, 8, 9, and almost any silicon pnp types for TRI, 3,
4, 5, provided collector voltage ratings are at least 12V
working in all cases. TR6 may be any small germanium
pnp audio power transistor, e.g. OC72 is also suitable.
The small diodes may be any silicon type with small self-
capacitance and at least 100V p.i.v. rating, D7 is a 5V
miniature Zener diode, D8 is a 500mW dissipation (at
least) 12V power Zener diode. Resistors should be
±10 per cent, except those connected to S2B, which must
be ±5 per cent, or better still ± I per cent. The specified
prototype semiconductors are all S.T.C./Intermetal types,
but in no way imperative.
TRI is a polarity inverter for those radiation detector
types feeding negative pulses to PLI. DI suppresses
positive pulses or components while D2 prevents overload
of TRI on excessive negative pulse amplitudes at PLI.
TR2 is the main pulse amplifier stage. It is fed at the
base with the positive output pulses from TRI collector,
as well as with the inputs of positive-pulse radiation de-
tectors connected to PL2 and/or PL3. D9 is included
here to prevent short-out of PL3 input by the low-
impedance output stage of a detector connected to
PL2, thus it is not necessary to disconnect the cables of
switched off detectors.
• (Ref to Fig. 2.1 for block diagram of STRACE Radiation Meter Unit.)
354
THRESHOLD LEVELS
VR1 is the collector load of the main pulse amplifier.
It is preset to give the response threshold levels marked
against PH to PL3. D4 suppresses negative pulses or
components at TR2 base, and D3 prevents overload of
TR2 if excessive positive pulse amplitudes are applied to
PL2 or PL3. The diodes Dl to D4 associated with TR1
and TR2 thus make the circuit very tolerant of large
differences in input pulse amplitudes. The performance
is still perfect even if the pulses fed to PL] , PL2 or PL3
are ten times larger than the specified threshold values.
Gain controls are thus not necessary on the front panel.
PULSE EXPANDER
TR3 is a driver emitter follower, to feed the pulse ex-
pander from the necessary low source impedance. The
pulse expander TR4/TR5 is a transistorised equivalent of
the valve-operated pulse expanders already introduced
last month in the gamma ray spectrometer kick-sorter
amplifier.
TR4 normally rests cut-off, and TR5 conducting.
When a trigger pulse arrives via C4, the roles of the two
transistors change over for a time determined by C9 or CIO
in conjunction with R19. Thereafter, the transistors
revert to the resting state of their own accord. The
duration of conduction of TR4 in response to each trigger
pulse from TR3 is independent of the form or duration of
that trigger pulse, being determined solelv bv C9, CIO
and R19.
PUMP INTEGRATOR
During each conduction pulse of TR4, a definite quantity
of positive charge is pumped via D6 and R20 into the
integrating capacitor C14. S2B switches the appropriate
discharge resistor across CI 4, to establish the different
c.p.m. ranges as discussed previously. The other wafer,
S2A* of the range switch selects C9 or CIO for determining
the pump pulse duration. On the lowest range (f.s.d.
100 c.p.m.), C9 is in circuit and gives a long pump pulse,
whereas the short pump pulse with CIO is used for all
other ranges.
The value of the integrating capacitor CI4 is 40>F, and
the net value of the discharge resistance (R32, VR4 and
the input impedance of the read-off voltmeter TR7, 8, 9)
is 4 megohms for both range 1 and range 2. Due to the
different pump pulse duration, range 1 is 100 c.p.m. and
range 2 is 250 c.p.m. for full-scale deflection, so that the
statistical accuracy is in fact somewhat poorer than 5 per
cent on range 1 but somewhat better than 5 per cent on
range 2 and all other ranges. This is a compromise made
to avoid unduly high values for CI 4, or unmanageably
high circuit resistances.
READ-OFF VOLTMETER
The read-off voltmeter for the integrator capacitor C14
comprises the remainder of the circuit on the right of
Fig. 7.1. The design figure is for a ImA fsd meter and/or
chart recorder connected to the output.
TR7, 8, 9 are cascaded current amplifiers to reduce the
current drain on the integrator capacitor CI 4 for the
voltage read-off process. VR3 sets a d.c. bias voltage
in series with C14 on ranges I and 2, to overcome the
silicon threshold of TR7, 8, 9. TR6 is in parallel with
VR3 and possesses a compensating temperature co-
efficient to cancel thermal drift of the threshold level of
TR7, 8, 9. TR6 must be positioned close to TR7, 8, 9
to sense the same temperature as the latter components.
VR6 and VR7 fulfil the same function as VR3 for the
other ranges. VR5 sets the meter sensitivity for all
ranges. D8 stabilises the supply voltage for all stages.
D7 limits the maximum voltage developed across CI 4, to
prevent damage to the meter Ml or TR7, 8, 9 if the range
switch is set to a range too low in relation to the input
pulse rate.
Next month: The remaining circuitry for the STRACE
radiation meter; this includes the pip generator, audio
amplifier, and power unit.
next month !
Build this
Radio-controlled
A pleasure to construct and a joy to run, this 34in
kit-built diesel-powered high speed craft carries a
multi-channel control system which will make it the
king-pin of any water on which it is sailed. Incor-
porates proportional rudder and progressive throttle
control for good manoeuvrability, with simultaneous
or one-at-a-time operation of these systems. Full
how-to-build instructions, with details of transmitter
and receiver (including control gear). Begins in next
month's issue. Don't miss it !
Other Constructional Projects include :
DRUMMER'S WHOOSH UNIT
CAMERA TRIGGER
PRACTICAL
ELECTRONICS
$55
SEMICONDUCTOR
ofltoiui
This serrt
used mej
6-OTHER SEMICONDUCTORS
By 6. |. KING
>iso far dealt with the more commonly
Ira of the semiconductor family, and in
this concluding article the aim is to consider briefly
some of the more recent developments using semi-
conductor materials.
TUNNEL DIODE
The tunnel diode action differs considerably from
the conventional diode. The main difference concerns
the reverse current characteristic which reveals that the
diode is highly conductive for all values of reverse
voltage (see Fig. 6.1 ); the forward current changes with
increasing forward voltage.
Initially, the forward current increases with forward
voltage in the normal way up to current f P due to
forward voltage V v . As the voltage is further increased
the current starts to fall, and subsequently falls into a
deep valley before it starts rising again to follow the
normal diode forward characteristic. This is called a
negative resistance characteristic because it is opposite
to ordinary resistive current flow.
NORMAL
FORWARD
CHARACTERISTIC
HICH
CONDUCTIVITY'
[REVERSE
i CURRENT
Fig. 6.1. Characteristics of tunnel diode. Note the negative
resistance zone and that high conductivity occurs in the
reverse direction
QUARTZ TUNNEL
CRYSTAL DIODE
Fig. 6.2.
diode
Simple crystal -controlled oscillator using tunnel
The depletion layer (potential barrier or "space
charge" region) is much narrower than in conventional
junction diodes due to a very high concentration of
/?- and n-type impurities in the basic crystal. Hence,
electrical charges are encouraged to traverse the
junction by an action called tunnelling.
In most applications the tunnel diode is biased so
that the operating point is established in the negative
resistance region, and it is suitable for use as an ampli-
fier, detector, oscillator, high-speed switch and rectifier.
This latter aspect may seem strange in view of the high
reverse conductivity.
Conventional rectifiers are arranged for substantial
current flow in the forward direction, but extremely
small in the reverse direction. Tunnel rectifiers, on
the other hand, are arranged for substantial reverse
current flow at very low voltages and much smaller
forward current due to the negative resistance effect.
This means that tunnel diodes can provide efficient
rectification at much smaller signal voltages than con-
ventional rectifiers, but note the reversed polarity
requirements (for which reason they are sometimes
called "back diodes").
Their amplifying attributes are particularly valuable
at microwave frequencies (above 300MHz) due to
low noise operation and low current demands.
Stabilisation assumes great importance when the
device is arranged as an amplifier, for it has a great
tendency to oscillate more freely than to amplify
without oscillating. This results from the wideband
negative resistance characteristic which, when the
amplifier is really well designed, can yield gain over a
bandwidth in excess of an octave without variable
tuning.
There is no trouble at all in getting a tunnel diode to
oscillate, even with only a fraction of a volt bias.
A basic oscillator circuit using a quartz crystal as con-
trol is given in Fig. 6.2. This yields a high range of
harmonics because as the diode oscillates it swings
continuously from the low voltage state, through the
unstable negative resistance region to the high voltage
state.
INTEGRATED SCREEN TRANSISTORS
Early transistors were troubled with a high output/
input feedback capacitance which called for neu-
tralising techniques in high gain amplifying applica-
tions to prevent the amplifier from changing into an
oscillator.
In ordinary transistors the unwanted feedback
capacitance stems from the comparatively large bonding
areas required for the emitter and base leadouts. The
+ 35V
4Tkfl
SATE Ifl GATE ID
^^ISOURCE ^-^SOURCE
(a) n-cbannei type (b) p-ehannel type
OUTPUT
INPUT
50pFS <IOkfl
CATHODE
N
6ATE
1
ANODE
Fig. 6.3. F.E.T. symbols
Fig. 6.4 F.E.T. audio amplifier circuit
Fig. 6.5. Make-up of silicon
controlled rectifier (see text)
effect of this causes a portion of the output signal to
get back to the input of the transistor in phase with the
real input signal, thereby creating conditions for
positive feedback. Even though oscillation may not
actually occur the effect can distort the response
characteristics of the amplifier.
The "integrated screen" is a section of diffused semi-
conductor beneath the base bonding area. Feedback
capacitance is considerably reduced making them
suitable for intermediate-frequency amplifiers in par-
ticular, Their use ensures that the response character-
istics retain a close tolerance even when the equipment
is mass produced.
FIELD EFFECT TRANSISTORS
The field effect transistor differs from the type of
transistor that we have looked at so far, in that it is a
voltage amplifier (as is the thermionic valve) rather
than a current amplifier. It has a very high input
impedance (millions rather than thousands of ohms)
stemming from reverse biasing of the input junction
required for normal operation. It will be recalled
that the ordinary transistor is biased on the emitter/base
junction for forward conduction, and it is this which
endows it with the relatively low input impedance.
Basically, the f.e.t. consists of a slice of high resistance
semiconductor sandwiched between two wafers of low
resistance semiconductor having either p- or //-type
characteristics. One end of the high resistance slice is
called the source and the other end the drain. The
two wafers are connected together to form what is
called the gate.
The f.e.t. also differs from the ordinary transistor in
that its action is governed only by one type of current
carrier — either the electron or the hole — and for this
reason it is sometimes termed "unipolar". Its symbol,
too, is different, as shown in Fig. 6.3, where (a) is an
n-channel type and (b) a /(-channel type, the carriers
being electrons and holes respectively.
Sectional view through a typical Texas f.e.t.
Fig. 6.4 shows basic f.e.t. amplifier stage, using an
n-channel device. While the drain polarity is positive
on the //-channel type, it is negative on a /^-channel
device, and the latter often incorporates a resistive
potential divider across the supply, with the junction
connected to the gate.
THYRISTOR
The thyristor (or silicon controlled rectifier) is a
junction diode with four semiconductor layers in npnp
formation, as shown in Fig. 6.5. The end /7-type is
called the "anode" and the end /j-type the "cathode".
The sandwiched p-type is the "gate" or triggering
electrode.
Owing to the four-layer make-up, current will not
flow from cathode to anode (or vice versa) under
ordinary conditions. However, when a pulse is
applied to the gate, current is allowed to flow in the
forward direction from anode to cathode.
When the polarity of the applied source is reversed
the thyristor, like an ordinary diode, only passes a
small leakage current. Unlike an ordinary diode, it
will not pass forward current again when the polarity
changes back, that is. not until it is once more gated
or triggered.
The gating pulse controls the instant during a
forward input pulse at which diode conduction starts.
Once triggered, conduction is maintained as long as
the supply polarity is correct and until the forward
current falls below a small holding value, fn this way,
the thyristor is considered as the semiconductor version
of the thyratron trigger valve.
STRAIN GAUGE PRINCIPLE
Finally, a word or two about the semiconductor
strain gauge principle. While the inherent resistivity
of a piece of semiconductor like silicon depends on the
various factors that we have already discussed, like the
addition of impurities, heat and light, it also depends
on mechanical strain. That is, by twisting, bending,
or straining a small chip of semiconductor the crystal
lattice is "distorted" and a change in resistivity occurs.
This is the basic strain gauge principle, currently
employed in various commercial and domestic devices.
A very interesting and fairly recent application of
the principle is adopted in the strain gauge pick-up
cartridge. The well-known crystal cartridge employs
the strain gauge principle, but more recently has been
replaced by the ceramic type. Very recent strain
gauge pick-ups use a very small chip of silicon, less
than 001 in long and less than 0000! in in cross section.
[MoMfi Owl ItetPMi QtDtp
AN ELECTRONIC SWITCH
Last month's beginners project explored the light
dependent resistor (I.d.r.) and its use as a "light-
operated switch". This month's project demonstrates
another "electronic" switch, namely the multivibrator.
The multivibrator is basically a two transistor circuit
in which one transistor is switched on and the other off,
i.e. the circuit 'has two distinct "states", and may. be
regarded as an electronic two-pole on/off switch,
sometimes referred to as a "Flip-Flop".
To demonstrate the action of the multivibrator, two
lamps have been inserted in the circuit and these flash
on and off as first one transistor is switched on and then
the other.
CIRCUIT
The circuit diagram (Fig. 1) has numbered circles,
which represent the terminal strip connections; these
are also indicated on the wiring diagram in Fig. 2.
The two transistors TR1 and TR2 employed in this
circuit are inexpensive npn types 2N2926 readily
available from most components shops, and advertised
elsewhere in the magazine.
The collector of TR1 is capacitively coupled to the
base of TR2 by CI, and the collector of TR2 is coupled
to the base of TR1 by C2. These capacitors are
electrolytic types and the polarities must be adhered to,
see Figs. 1 and 2,
The cross-coupling of the multivibrator circuit
produces what, in effect, is an oscillator, due to the
feedback action of the capacitors. Oscillation is
started by the unbalance in each half of the circuit due
to component tolerances. The output waveform at the
collector of each transistor is almost square.
THE OPERATION
When power is first applied to the circuit from the
battery the unbalance between each half of the circuit
RY1.
9V.
Mm oritur
^ronvstor c . e «|kclor
°°* b-tMM
2H2«6
pushes one transistor towards current cut-off and the
other towards full conduction.
Let us assume at the start that TR1 and LP1 is
switched on and TR2 is off; the voltage at TR1 collector
charges CI because the collector end of CI is less
negative than the base of TR2. At the same time, the
base of TR2 becomes negative bringing it into con-
duction from its off state and switches LP2 on.
The capacitor CI discharges through VR1 and C2
starts charging, making the base of TR1 go negative.
The result is alternative conduction through TR1
and TR2.
The flow of current in the base of the transistors
causes a larger flow of current in the collectors and it is
this larger current which drives the lamps.
The timing of the switch-over is determined by the
values of the capacitors, the amount of charge on them,
and the value of resistors Rl, R2, and VR1, through
which the charge leaks away.
SWITCHING TIME ADJUSTMENT
By adjusting the setting of the potentiometer VR1,
the value of the resistance affecting the discharge of each
capacitor can be altered to change the switching time,
so that one bulb will be on for a different period of
time compared with the other. In fact, as one bulb
comes on for a longer time, the other does so for a
shorter time.* This is called altering the mark-to-space
ratio of the generated waveform.
Fig. I . Circuit diagram of the multivibrator. The numbered
circles represent the terminal strip connections
Fig. 2 Constructional and wiring details. Note the transistor
and capacitor connections
Low consumption 6V lamps are used with a current
rating of 0-06A (60mA), but lamps rated at 01 A
(100mA) will work just as well. Higher ratings should
not to be used unless the transistors are changed for
higher current types.
USING PNP TRANSISTORS
If the reader wishes to use pnp transistors the
capacitor polarities must be changed round, i.e. the
positive ends are connected to the bases of the transis-
tors. Also, the battery connections will have to be
reversed, i.e. negative terminal connected to the lamps,
CONSTRUCTION
Commence the construction by cutting a softwood
baseboard Sin x 5in x |in. The next stage is to wire
the 12-way terminal strip before mounting this in
position on the baseboard. A plastics sleeved link
wire should be inserted between terminals 1 and 12.
The two resistors Rl and R2 should be positioned
between terminals 3 and 6; 8 and 10.
The outer leads of the subminiature potentiometer
VRI should be carefully bent so that they can be
inserted in terminals 6, 7, and 8, see Fig. 2. The
electrolytic capacitors CI and C2 are positioned in
terminals 2 and 10, 3 and 11. It is important that CI
and C2 are wired to the correct terminals; reference
should be made to Fig. 2.
Finally, before mounting the terminal strip on the
baseboard, the transistors should be mounted on the
strip, see Fig, 2. Particular care should be taken to
ensure that the transistor leads are wired to the correct
terminals, as they can be damaged if wired incorrectly.
FINAL ASSEMBLY
The terminal strip and m.e.s. bulb holders can now be
screwed to the baseboard, see wiring diagram for
relative positions. The terminal strip should be
checked against the wiring diagram and screwed to the
baseboard with two |in No. 4 countersunk woodscrews.
The m.e.s. bulb holders are screwed to the baseboard
with four iin No. 4 countersunk wood screws.
COMPONENTS
Resistors
Rl 2-2kQ R2 2-2kO
10%, £ watt carbon
Potentiometer
VRI lOkO linear subminiature preset
Capacitors
CI, 2 50/xF electrolytic, 12V (2 off)
Transistors
TRI.2 2N2926(2off)
Lamps
LP I, 2 6 V 0-06A (60mA) (2 off)
Miscellaneous
BY I 9 V type PP9 battery
One 12-way plastics terminal block
Two m.e.s. bulb holders, batten mounting
Wooden baseboard Sin x Sin X ^in
Two miniature crocodile clips or battery connectors
Six fin No. 4 countersunk wood screws
Plastic covered, single core copper wire
Total cost £1 approx.
A lead from terminal 1 1 is taken to LP2 bulb holder.
Two leads are taken from the other connecting screw
and wired to terminal 8 and LP I bulb holder, see
Fig. 2. The other connecting screw of LP1 should be
wired to terminal 2.
Finally, the battery leads should be wired in circuit.
The negative lead is taken from terminal 1 and clipped
on the battery negative connector by a miniature
crocodile clip. The battery positive lead is taken from
terminal connecting both lamps together.
The crocodile clip acts as a simple switch if removed
when not used. All the wiring should be given a final
check before making the final battery connection.
The multivibrator lamps will start flashing or switching
on and off as soon as the supply is connected.
All components wired to
the terminal strip. Note
the link wire
Fixing a connecting lead to one of the m.e.s. bulb holders
The completed multivibrator 1
The detailed explanation concerning the operation of
UNIT "A" is continued in this month's article,
with further practical examples.
We resume by considering the use of the operational
amplifier as an integrator.
An operational amplifier will be handling time as well
as voltage when acting as an integrator, so some means
must be found of inserting intervals of time onto the
computer. One method is to employ external oscil-
lators to provide known functions of time in terms of
frequency. An input to an integrator might consist
of a steady d.c. voltage which is switched on for a time t
(step function or square wave), or alternatively, a sinu-
soidal voltage of frequency /and period 1//.
If a graph is drawn of the resulting integrator output
function, and this is the form that answers to problems
involving change or motion will usually take, the X axis
of the graph will be calibrated in intervals of time, with
voltage on the Y axis. It follows that an oscilloscope,
which also uses time on the X axis and voltage on the
Y axis, can provide a convenient form of output dis-
play, especially when an integrator is operating at high
speed.
The operational amplifier is converted to an inte-
grator when a capacitor Cr is inserted, in place of a
resistor, in the feedback path; see Fig. 5.1, When an
input voltage —E- in is applied to the integrator by
means of a simple switch S for a time f, the output £
will take the form of an increasing ramp voltage pro-
portional to t with slope
~F t J—
-KinCf
Note that the operational amplifier will continue to
invert an input voltage even when used as an integrator.
THE INTEGRATOR IN EQUATION
SOLVING
The electronic analogue computer does provide a
powerful technique for obtaining rapid solutions to
problems involving calculus, which cannot be equalled
either by numerical methods or by a digital computer.
If differentiation and integration are regarded as
straightforward mathematical operations, it will be
found that the terms of, say, a second order differential
equation can be manipulated on the computer in much
the same way as the terms of a "steady state" algebraic
equation.
For example, whsn an equation term y is differen-
tiated against time its derivative dyjdt is obtained, and
a second differentiation yields the second derivative
d 2 yjdt 2 . The reverse process is where integration of the
second derivative d 2 v/df 2 produces the first derivative
dyldt, and another integration gives y as the result.
Fig. 5.2 shows how a simple integrator can handle
equation terms. Combined operations are made
possible by cascading integrators, while using coefficient
potentiometers and computing component ratios for
summation, multiplication, and division (Fig. 4.1).
The process of differentiation, although feasible if
care is taken, is generally avoided on analogue com-
puters because it gives rise to unstable operational
amplifier configurations, but this imposes only a slight
limitation since integration can be employed— in the
majority of cases — in place of differentiation.
INTEGRATOR ACCURACY
The transfer accuracy of an operational amplifier,
when it is used as an integrator, will be theoretically
limited by its finite value of open- loop gain. However,
©©^[Ptyjir
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per 100.
TRANSISTOR BABO AIH SALE I
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OC71, OC72 equivalent
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Transistor Driver Transformers 8/6 each!
Transistor Output Transformers (nil bible for our kits above I . . . . 8/6 each!
0C28 Equivalent til- each!
BYZ13, S amp rretJtters 8/6 each:
Light Benaltlvltv transistors similar to OCP71 ■ ■ V- each!
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RECORD PLAYER CARTRIDGES
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TER0B0ARD. All sixes in .took
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," in 0-15 matrix
2frin 0-la matrix
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51u
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3!ln
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31 in
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til tnatri.x
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(! 1 matrix
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Through this ICS
3- way Training Method:
H
MASTER THE THEORETICAL SIDE
From basic principles to advanced applications,
you'll learn the theory of electronic engineering,
quickly and easily through ICS. That's because
each course is set out in easy-to-understand terms.
MASTER THE PRACTICAL SIDE
ICS show you how to develop your practical
abilities in electronic engineering— alongside your
theoretical studies. It's the only sure way to
success. All training manuals are packed with
easy-to-follow illustrations.
MASTER THE MATHEMATICAL SIDE
To many this aspect is a bitter problem. Even
more so because no electronic engineer is complete
without- a sound working knowledge of maths.
But new ICS teaching makes mathematics easier
to learn.
Wide range of courses available include:
Radio/TV Engineering and Servicing, Closed Circuit TV, Electronics,
Electronic Maintenance, Servo mechanisms, Computer Engineering,
Numerical Control Electronics, etc.
EXPERT COACHING FOR:
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Build your own radio, tranttttor portable, and profeulonal-type test
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supplied. For details past coupon below.
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PRINTED CIRCUIT KIT
BUILD 40 INTERESTING PROJECTS on m PRINTED CIRCUIT
CHASSIS with PARTS and TRANSISTORS from your SPARES BOX
CONTENTS: (I) 2 Copper Laminate Boards 4±- x 2i". (2) I Board for Match-
box Radio. (3) 1 Board for Wristwatch Radio, etc, (4) Resist. (5) Resist
Solvent. <6) Etchant. (7) Cleanser/ Degreaser. (B) 16-page Booklet Printed
Circuit! far Amateur;. (9) 2 Miniature Radio Diatj SW/MW/LW. Also free
with each kit. (10) Essential Design Data, Circuits, Chassis Plans, etc. For
40 TRANSISTORISED PROJECTS
A very comprehensive selection of circuits to suit everyone's requirements
and constructional ability. Many recently developed very efficient designs
published for the first time, including 10 new circuits,
EXPERIMENTER'S
PRINTED CIRCUIT KIT
8/6
Postage & Pack. 1/6 (UK)
Commonwealth:
SURFACE MAIL 2/-
AIR MAIL B/-
Australia, New Zealand,
South Africa, Canada
(I) Crystal Set with biased Detector. (2) Crystal Set with voliage-quadrupler
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Audio Amplifier. (SJ Carrier Power Conversion Receiver. (6) Split-Load
Neutralised Double Reflex. (7) Matchbox or Photocell Radio. (8) "TRI-
FLEXON" Triple Reflex with self-adjusting regeneration (Patent Pending).
N§ Solar Battery Loudspeaker Radio. The smallest 3 designs yet offered to
the Home Constructor anywhere in the World. 3 5ubminiature Radio Receivers
based on the "Triflexon" circuit. Let us know if you know of a smaller
design published anywhere. (10) Postage Stamp Radio. Size only 1-62* X '95*
x -25-. (II) Wristwatch Radio 115* x -80' x -55*. (12) Ring Radio -70* x
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Control Tone Receiver, ( IS) Transistor P/P Amplifier. (I6> Intercom. (17)
I -valve Amplifier, (IB) Reliable Burglar Alarm. (19) Light-Seeking Animal,
Guided Missile. (20) Perpetual Motion Machine. <2I> Metal Detector. (22)
Transistor Tester. (23) Human Body Radiation Detector. (24) Man/Woman
Discriminator. (25) Signal Injector. (26) Pocket Transceiver (Licence required).
(27) Constant Volume Intercom. (2B) Remote Control of Models by Induction.
(29) Inductive-Loop Transmitter. (30) Pocket Triple Reflex Radio. (31) Wrist-
watch Transmitter/Wire-less Microphone. (32) Wire-less Door Bell. (33)
Ultrasonic Switch/Alarm. (14) Stereo Preamplifier. (35) Quality Stereo Push-
Pull Amplifier. (36) Light-Beam Telephone "Photophone". (37) Light-Beam
Transmitter. (38) Silent TV Sound Adaptor. (39) Ultrasonic Transmitter,
(40>Thyristor Drill Speed Controller,
PHOTOELECTRIC KIT
CONTENTS: 2 P.C. Chassis Boards. Chemicals, Etching Manual, Cadmium
Sulphide Photocell, Latching Relay, 2 Transistors, Condenser, Resistors,
Gain Control, Terminal Block, Elegant Case, Screws, etc. In fact everything
you need to build a Steady-Light Photo-Switch/Counter/Burglar Alarm, etc.
(Project No, 1 ) which can be modified for modulated-!! ght operation.
PHOTOELECTRIC KIT
39/6
Postage & Pack. 2/6 (UK)
Commonwealth;
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AIR MAIL £1.0.0
Australia, New Zealand,
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Alto Essential Data Circuits
and Plans for Building
12 PHOTOELECTRIC PROIECTS. (I) Steady-Light Photo-Switch/Alarm. (2)
Modulated-Light Alarm. (3) Long-Range Stray-light Alarm. (4) Relay-Less
Alarm. (5) Warbling-Tone Alarm. (6) Closed-Loop Alarm. (7) Projector Lamp
Stabiliser. (8) Electronic Projector Modulator. (9) Mains Power Supply.
(10) Car Parking Lamp Switch. (II) Automatic Headlamp Dipper. (12) Super-
Sensitive Alarm.
INVISIBLE BEAM OPTICAL KIT
Everything needed (except plywood) for building: I, Invisible-Brain Projector
and I Photocell Receiver (as illustrated). Suitable for -ill Photoelectric Burglar
Alarm*,, Counters, Door Openers, etc.
CONTENTS: 2 lenses, 2 mirrors, 1 45*degree wooden blocks, Infra-red filter,
projector lamp holder, building plans, performance data, etc Price 19/6*
Pottage and Pack 1/6 (UK). Commonwealth; Surface Mail 2{-; Air Mail 8/-.
JUNIOR PHOTOELECTRIC KIT
Versatile Invisible-beam, Relay-less, Steady-light Photo-Switch. Burglar
Alarm, Door Opener, Counter, etc., for the Experimenter.
CONTENTS: Infra-Red Sensitive Phototransistor, 3 Transistors, Chassis,
Plastic Case, Resistors, Screws, etc., Full Size Plans, Instructions, Data
Sheet "10 Advanced Photoelectric Designs".
Price 1 9; 6. Postage and pack. 1/6 (UK).
SUBMINIATURE SOLAR BATTERY. 10/6. Post and pack. I/-,
Output in Bright Sunlight: 7 v./2S0 microamps.
Build that Sun Powered Wristwatch Radio for your Holiday and amaze
your friends. Plans supplied free with each battery.
YORK ELECTRICS, 333 York Road, London, S.W.11
Send a S.A.E. for futi dettfjJx, a brief description and Photographs of all Kits and
alt 52 Radio, Electronic end Photoelectric Projects Assembled*
SILICON RADIATION DETECTOR
The NUTRONICS semiconductor radiation
detector ND7 is a compact, low cost, versatile
radiation detector with a window area of
7mm2 and Alpha energy resolution of 50-100
Kev, FWHM, which has been expressly
designed for use in educational establishments
and by amateur experimenters.
The NUTRONICS semiconductor radiation
detector ND7 detects Alphas, Beta, Gamma
Radiation, Fission Fragments, X-rays and
Protons.
Send for technical data sheet,
SOLID STATE NUTRONICS LTD. t.i.
SA Voltaire Road, London, S.W.4 01-874 8608
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362
TABLE 5.1
c f
Rin
t
IjttF
tOOkfi
i ok a
2-8sec
800ms
O-I^F
lOOkQ
ioka
280ms
80ms
0-0 VF
lookn
28ms
Maximum value of
t for an error
of
%
the situation is much more complicated than with, for
example, a summing amplifier (Fig. 3.8) since the
amplifier error can no longer be defined in terms of the
simple relationship between closed-loop and open-loop
gains.
As a guiding principle, integrating amplifiers may
have very large values of closed-loop gain provided
that the time t of an input function remains small.
Closed-loop integrator gains of 1,000 or more are not
uncommon in transistor computers, since low voltages
and low impedances discourage the use of computing
resistors of more than 100 kilohm, and capacitors of
more than 1/*F are too bulky. Table 5.1 is calculated
for UNIT "A" amplifiers, and sets out the maximum
allowable interval / for selected values of Ct and Ri n ,
where the amplifier transfer error must not exceed
one per cent.
Errors due to unwanted drift voltages also become
significant when t is long and Ct is small. The greatest
care must be exercised when zero-setting integrators to
eliminate offset voltages, for good accuracy at long
time intervals. Also, the computer should not be
subjected to fluctuations of ambient temperature when
computations cover several hours of integrator use.
COMPUTING CAPACITORS
The computing capacitors used for PEAC will
normally He within the range 001-1/tF, and the three
values most commonly employed are 0-01/iF, 01/fF,
and 1/fF. Polystyrene is the preferred capacitor
dielectric, for high insulation resistance, but polyester
makes an acceptable second best. Mica, paper, and
ceramic capacitors should be avoided.
Small value polystyrene capacitors of ±1 per cent
and ±2 per cent tolerance are easily obtained, but
0-1 fi¥ and I/*F precision components are rare and
expensive. To get around this difficulty, the bridge
circuit of Fig. 5.3 was devised to allow computing
capacitors to be made up from specially selected low
cost ±20 per cent capacitors.
The circuit of Fig. 5.3 can be constructed in bread-
board form on Verobojird or s.r.b.p., with miniature
sockets to take C x and Rl. If an audio signal gener-
ator is not available to supply the bridge with about
10V r.m.s. at 1kHz, a signal could be obtained from a
transistor multivibrator powered by the 25V computer
power supply. Headphones serve to detect the null
point when the bridge is in balance, and should have
an impedance of about 2 kilohms.
The method of making up a computing capacitor of,
say, 1/iF is as follows. A capacitor panel of plain or
perforated s.r.b.p. is fitted with small turret tags as in
Fig. 5.4. A ±20 per cent capacitor of about 0*68^F is
wired into position on the capacitor panel before it is
plugged into the bridge C x sockets, and a 1 kilohm
f •"*"* In a. V V0LT5/SEC
Fig. S.I. The operational amplifier as an integrator
BASIC OPERATIONS IN CIRCUIT FORM
fl in
yo Wr
AY
-4^> I o
^ -a/Cd/
RtG
fW
fi
INTEGRATION
SYMBOL
yo— a
-oyv it
*{r>*
Fig, S.2. The handling of equation terms by a simple
integrator
■ nlft"!
10V RMS.
Q-ljiF 10Mi±1%
IjtF lkfi + 1%
I
111!
ci
t0,000pF
100kfl
i O O n
HIGH I
TTT
* 1000 XR1
n
Fig. 5.3. Bridge circuit used for making up computing
capacitors
TURRET TAGS
20 S.W.G. TINNED
COPPER WIRE
Fig. 5.4. Computing capacitor plug-in panel
363
resistor is inserted for Rl. Assorted polystyrene or
good quality polyester capacitors of lower value are
then temporarily connected across the capacitor panel
to increase Cx by small increments, while listening on
the headphones for a drop in the level of the 1kHz
tone as Cx approaches 1/*F.
A typical computing capacitor might finally consist of
a parallel combination of the following values, 0*68/tF,
0-22/iF, 002/xF, and 0005/tF.
If the required value of C x is exceeded, the note in
the headphones will increase in volume when the null
point is passed. Allow capacitors to cool off after
soldering, and before making a measurement, as heat
can cause a temporary or permanent change in capaci-
tance. With the Fig, 5,3 bridge circuit it is possible
to detect increments of less than OOl/^F in a nominal
1/aF capacitor.
DIFFERENTIAL ANALYSIS WITH
UNIT "A"
A second order linear differential equation with
constant coefficients has become firmly established as
the "classic" introduction to differential analysis on
the analogue computer.
The equation describes an oscillatory system with
variable damping which can be used to simulate
indirectly many physical systems, such as the spring
pendulum, a tuned LC circuit, or a servomechanism.
Also, the equation is easy to set up on the computer,
and does not necessarily demand the use of integrator
mode switching.
In general form the equation is,
aS + 6^ + cv=/(/)
df s
dt
(Eq. 5.1)
where a, b, and c are the constant coefficients, y is
unknown, and /(/) represents some function of time.
Equation 5.1 can be rewritten to suit a particular
system by substituting appropriate terms.
Spring pendulum
m d? + /t d7 + ^ =/( ' )
(Eq. 5.2)
where m is the mass of a weight suspended on a spring
of constant k, which is damped by friction fi. The
weight is displaced by an amount v when subjected to a
force dependent on/(/).
Tuned LC circuit
j €®
** dr*
*§ +*<>-/«
(Eq. 5.3)
where L is an inductance tuned by a capacitance C, and
damped by a series resistance R. Q is the charge in
coulombs on C at any instant of time. The current
flowing in the tuned circuit is given by dQIdt, and /(f)
represents an input function.
Ser vomechanism
d 2 o , ,„ dd a .
w 2 0i (Eq. 5.4)
where o is the angular displacement of the output
shaft, £ the damping factor, m the angular velocity, and
0i the angular displacement of the input shaft.
The obvious similarity between the above equations is
emphasised when, in Fig. 5.5, it is seen that they all have
virtually the same problem layout on the computer.
Furthermore, as the computer will allow operation at
almost any fraction or multiple of real time, a spring
pendulum and a tuned LC circuit can be simulated
simultaneously, and interesting electro-mechanical
parallels can be seen to exist between the properties of
inductance and mass, resistance and friction, and capa-
citance and elasticity.
The only real difference between the analogous
behaviour of a weight on a spring, a servo shaft, and a
tuned LC circuit is that the LC combination will nor-
mally resonate at a much higher frequency.
PROBLEM EXAMPLE 3.
TUNED CIRCUIT ANALYSIS
UNIT "A" will simulate any series tuned circuit by
solving Equation 5.2, and will give answers in the form
of a.c. meter readings or oscillograms. Tuned circuits
resonating in the MHz region are catered for by slowing
down the problem to some convenient decadal fraction
of real time, so that a simulated circuit on the computer
which is, for example, resonating at 300Hz, will serve
as a model for a real circuit resonating at 30 MHz, with
suitable rescaling of L, C, and t.
To initially determine the relative values of L, C, R,
voltage V, and current /, without too much paperwork,
it is helpful to start with a representative tuned circuit
which allows computer operation in real time, at
frequencies convenient for display by an a.c. voltmeter
or an oscilloscope. 50Hz is a good frequency to
employ as a datum because it can be readily obtained
from the mains supply, and rounded values of L = 1 H
and C = 10/fF will also offer resonance at 50Hz.
Taking the circuit of Fig. 5.6a as a starting point,
from the knowledge that a series tuned circuit will
exhibit an impedance equal to R at resonance, the
r.m.s. current flow at 50Hz will be Ei[R, or 20mA when
E\ - 2V r.m.s. and R = 100 ohms.
It is necessary to rearrange the basic equation.
Equation 5.2, for the computer by dividing through by
L, and solving for the second derivative.
Substituting known values from Fig. 5.6a,
d z e 100R dQ I
Q +
dt 2 ' 1H dr 1H x 10- 5 C~ ' 1H
(Eq. 5.6)
f{t) in the present case represents a sine wave input of
2V r.m.s. In other circumstances the input function
could be a square wave of amplitude E\ n and period 2/.
Equation 5.6 is solved on the computer by successive
integration. Looking at the symbolised diagram of
Fig. 5.6b, it can be seen that there are two closed-loops,
one linking the output of OA1 viaCPl to OAl/Input 1,
and the other passing through OA1, OA2, and OA3,
v4a CP2, and thence back to OAl/Input 3. The
coefficient of CP1 will be multiplied by the gain factor
associated with OAl/Input 1. CP2 coefficient is
multiplied by the product of gains OAl/Input 3, OA2,
and OA3, i.e. 1,000 x 100 x 1 = 100,000.
d 2 Q/dt 2 , obtained from the sum of the voltages
present at the inputs of OA1, is initially assumed to be
present. After one integration OA1 provides an
output dQIdt, and from this all the terms on the right
hand side of Equation 5.6 are assembled. So, dQjdt is
multiplied by R/L = 100, using CP1 set for a coefficient
of 0*1, and is taken back to OAl/Input 1 where it is then
added to f(t)/L = 2V r.m.s.
364
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Moving in the other direction on the symbolised
diagram of Fig. 5.6b, dQjdt is integrated by OA2 to
obtain +Q. Inverting amplifier OA3 changes the
sign of Q before passing it on for multiplication by
1/LC = 100,000 (CP2 coefficient of I). - (]/LC)Q is
then added, at OA1 /Input 3, to
L d/ + L
and the sum of all OA1 input voltages yields the re-
quired d 2 Q/df 2 . Because there are two closed-loops
in the computer set-up the equation will be self-
enforcing.
Routine. Switch on UNIT "A" power supply and
allow a warm-up time of at least 1 5 minutes. Ensure
that the three operational amplifiers are disconnected
from their summer networks, and have no feedback
components. Apply 10V d.c. voltmeter leads to
OA1/SK13 and an earth socket, and zero-set OA1 for
an output voltage of less than ± 1 V from the back of the
UNIT "A" box, by means of VR1 (Fig. 3.7). Repeat
for OA2 and OA3.
Set up the problem according to the patching circuit
of Fig. 5.6b, but omit the feedback capacitors and the
patching link between OA3/SK13 and CP2/SK1.
Set CP1 dial to approximately "1". Connect the volt-
meter to miniature socket OA1/SK6 (Fig, 2.9) and
zero-set OA1 again, but this time using the front
panel control VR15.
Next, zero-set OA2 using VR16, and OA3 using
VR17. Insert 0-I/tF computing capacitors into OA1/
SK11 and SK12, and OA2/SK1I and SK12, and make
good the link between OA3 output and CP2. Set CP2
for a dial reading of "10". Apply the voltmeter to
OA2/SK.7 and zero-set the complete assembly of
amplifiers by adjustment of VR15(OAI) only.
The problem layout will now be ready for dynamic
checks and should not need to be re-zeroed for several
hours if UNIT "A" is being operated in stable ambient
temperature conditions.
_A iy
a it
rOH
77* a it a r o
o
COMPUTER LAYOUT FOR S0LUTI0H OF SECOND ORDER EQUATION
dH m it *> i»
'\Jjl_TI\w: — 1\-,
a
LAYOUT TO SIMULATE THE MOTION OF A SPRING PENDULUM
R iO
L it
to
M 1
O 1
-m°
4Q
it '
rg _ « do i a . *£}
it 1 L it ~LC V L
CURRENT 7-
~^ — l>i
o
LC
CHAffeE |
I o V>-|
LAYOUT TO SIMULATE A TUNED CIRCUIT
it 2 dSp i _^ I
~P^> * dr IX ^ *** r^y*''
<yL
LAYOUT TO SIMULATE OVERSHOOT IN A SERVO SYSTEM
Fig. 5 .5. A second order differential equation applied to physical systems
367
TABLE 5.2
SHOWING HOW COMPUTER OPERATING FREQUENCIES ARE
RELATED TO CP2 SETTING AND AMPLIFIER CLOSED-LOOP GAINS
Resonant
Frequency
f
Typical
Values
L C
CP2 J_ Amplifier Gains
Coefficient LC OAI OA2 OA3
Input 3
005Hz
I.000H
I0,Q00 M F
1
0-1
to
10
0-1
0-5Hz
I00H
I.OOO^F
10
10
10
10
01
5Hz
I0H
I00^F
001
I0 3
1,000
100
10
to
50Hz
IH
I0^F
10
I0 5
1,000
100
1-0
500Hz
IQOmH
I^F
10
io r
1.000
'.ooo
10
IkHz
lOOmH
0-VF
to
5x io*
1,000
1.000
50
]. —
£in
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C-tOjjF
1H
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*-100fl
— w» —
/-20 mA
TUNEO
CIRCUIT
RESONATES
AT50H*
REPRESENTATIVE TUNED CIRCUIT USED FOR SETTING UP
THE PROBLEM LAYOUT IN "REAL TIME"
fin
INPUT 1
rm N
L INPUT 2
SYMBOLIZED DIAGRAM
INPUT
2V UU
50 Hi
1 0A3
Or!
DYNAMIC CHECK VOLTAGES,
AND POT SETTINGS SHOWN THUS
2V
r.m.i.
-0
f
[CPI
INPUT1
INPUT
FUNCTION I INPUT
INPUT 2 lOOkOl f\
. ifcJDJ IT T */\i. A W^
PUT 3 Wkll
C, O-liiF
HI-
2^-= 100,000
Fig. 5.6. Programme layouts
for tuned circuit analysis
1 r
100kQ
C f 0-1uf
-II-
T>
I SUMMER 2 AND
i r
i
i
T
i
I
ttkO.
~l
1>
i SUMMER 3 AND
w^l«l«!!)_of:*MM_. I Lit.* M - p -i I l*!*!!!? I
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SIMPLIFIED PATCHING CIRCUIT
368
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Electronically changes speed
rom approximately 10 revs, to
tsocimum. Full power at
all speeds by fingertip control.
Kit Includes all parts, case,
everything and full Instruc-
tions 10/8, plus 2/6 post
and insurance. Or available
made up 32/8, plus 2/0 post and insurance
SUPERTONE G.C.V.
Saras »ou work—
It's partly bail!
Like Its predecessors this latest Companion
has full ft performance— such aa only a
good wooden cabinet anil billux speaker can
give, and due to its being partly built you will ,
have It going in an evening. Sett Lhea*
features.
• 7 Transistors, superhcl circuit.
• Two-tone Cabinet, size 1 1 ■;< 6 / 3in.
• All circuit requirements — Push-pull out-
put — A.Y.C. and feed back, etc.
Printed circuit board all wired only con-
nections, e.g., to Volume control" W.C",
Switch ami Tuning Condenser,
• Pre-allgned IF stages complete with full trust r*e lions. Pi let nnh- £4.9.8 plus
6/0 post ami insurance.
RADIO STETHOSCOPE
Easiest wiy to lault find - traces signal {rom aerial to
speaker— when signal stops you've found the fault. Use
it on Radio, T.V., amplifier, anything • complete kit com-
prises two special transistors and all parts including probe
tube and crystal enrpWc 298— twin stctiwet III if (mil ot
earpiece 7/6 extra
post and Ins. 2/9.
THIS MONTH'S SNIP"
MICRO-SONIC
7 transistor Key chain Radio in verv
pretty case, size 2 J in :< 2Jin ;: liin "
complete with soft leather zipped bag.
Specification: Circuit— 7 transistor
superhcterotlvuc ; Frequency range —
1530 to l.OOOkc/s; Sensitivity— omV.'di:
Intermediate f re que ney — 465ki '.» . n i
453kc/s; Power output — 40oilV;
Antenna— ferrite rod; Loudspeaker—
Permanent magnet type. In transit
from the East these sets suffered slight
corrosion as the batteries were left in
them but when this corrosion is cleared
away they should work perfectly-
offered without guarantee except ih:<i
they are new, 18/0 plus 2/0 post and
insurance, less batteries.
BATTERY OPERATED TAPE
DECK
With Capstan control. This unit is extretnely
well made ami measures appro*. 6 :< 8 x 2ln
deep. Has three piano key type controls lor
Kecord, Playback and Rewind. Motor Is
a special heavy duty t ype Intended tor
operation off 4/5 volts, .Supplied complete
with 2 spools ready to install. Record,
Replay head Is the sensitive M4 tvpe intended
for use with transistor, amplifier, PrJrv
*4.'16,'-. Post and insurance 4/0.
RECORD PLAYER SNIP
The "Princess" 4 speed auto
mntlc record changer and player
engineered with the utmost pre-
cision for beauty, long life and
trouble free service. Will take
up to ten records which may be
mixed— Tin. lOin or 121n.'Patent
stylus brush cleans stylus after
each playing and at shut off, the
pick-up locks itseK Into Its recess
— a most useful feature with port-
able equipment — other features
include pick-up height adjust-
ment and sfylus pressure adjust-
ment. This truly Is n tine instru-
ment which you can purchase
this month at only (5.19,6, complete with
Post and insurance 7/0 extra.
art ridge and ready to pin
CASSETTE LOADED DICTATING MACHINE
Batter)' operated and tilth all accessories.
Really fantastic offer, a British mad.'
£31 outfit tor only 18/19/6, brilliant Iv
designed for speeil and efficiency- -
cassette takes normal spools, drops In
and out for easy loading— all normal
functions — accessories include Btetho-
scopie ear-piece— cry >ti J microphone
has on/off switch — telephone pick-up-
take reference pad — DON'T MISS
THIS UNREPEATABLE OFFER-
SEND TO-DAY. #,8/19/6, plus 7/0 post
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Spare Cassettes at 7/6 each, three for £1.
SEHSITIVE
HAND MICROPHONE
Dynamic type. Low Impedance, moving
ion, fitted In mutually neat plastic head
with ant i -microphonic coupling to
handle. Extra small size'Wt very sen-
sitive. 15;'- each.
B7GJ ValTS Holders with bottom screen—
p.t.f.e. insulation finest for HP and
VHF, 1/- each : 10/- doz.
Fractional H.P. Motor. 240V o0c/«—
open construction Ideal for ventilation
fan — Mower heater, etc.
Clock Motor. 230V GOc'ft synchronous— self
starling, 6/6.
Pentode Output Transformer— standard siie,
40-1 , ex equipment but O.K., 4/3 each; 48 '- doz.,
post paid.
Jfeon Main* Tester, 1.3 each ; 12/- doz.
MAINS TRANSFORMER. Upright mounting with
primary tapped 200, 220, 240V H.T. secondary is
250-0-26W at 100mA and it has two L.T. secon-
daries of 6-3V 1JA — unused (removed from
equipment), IS/- plus 3/fl poet and insurance.
FLUORESCENT CONTROL KITS
Each kit comprises seven Items — Choke, 2 tube
ends, starter, starter holder and 2 tube clips.
with wiring instructions. Suitable lor normal
fluorescent tubes or the new "Orolux" tubes for
fish tanks and Indoor plants. Chokes are super-
silent, mostly resin Ailed. Kit A.— 15-20W. 19/6.
Kit B-30-40W., 17/8. Kit C— SOW., 17/6.
Kit I>— 126W., B2/-. Kit E— 6oW„ 19/6. Kit
MF1 is lor Sin., Oin. and 12in. miniature tubes
19/8. Postage on Kits A ami B 4/6 for one or two
kits then 4/6 lor each two kits ordered. Kit* C
D and K 4/6 on first kit then 3/0 for each kit
ordered. Kit MF1 3/6 on first kit then 3/6 on
each two kits ordered.
MAINS TRANSISTOR POWER PACK
Designed ttf operate transistor sets and amplifiers.
Adjustable output 6V, »V, 12V for up to 000mA
(class B working). Takes the place of any ot
the following batteries: PP1, FP3, PP4, PP6.,
FP7, PPit, and others. Kit comprises; mains
transformer rectifier, smoothing and load resistor,
condensers and Instructions. Real snip at only
16/6, plus 3/0 postage.
MAINS MOTOR
Precision made — ns used
in record decks and tape
recorders — ideal also for
extractor fan blower
heater, etc. New and
perfect. Snip at 9/6.
Postage 3/- ior first
one then 1/- for each
■-^Ii one ordered. 12
and over post
free,
RELAY SWITCHES. Tbese enable micro switches,
delicate thermostats or other low current devices
to control up to 30A. Ideal to switch thermal
storage heaters — motors, etc., made by the
famous AEI group these arc listed at £25 each —
you can buy if you hurry at a very keen price of
39/6 each and we will include diagrams and data.
Moulded on panel size appro*. 6 x 7 ;■; 2ln deep
THERMOSTATS
Type "A" I5A for controlling room heaters,
greenhouse, airing cupboard. Has spindle for
pointer knob. Quickly adjustable from 30-80°F.
fl/6 plus 1/- poet. Suitable box for wall mounting
5/- P. A P. I/-.
Type "B" ISA. This Is a I7ln long rod type
made by the famous Sunvle Co. Spindle adjusts
this from 30-050° F. Internal screw-
§ alters the setting so this could be
adjustable over SO' to I.fKKPF. Suitable
** *•»> ■ " ' ■■ ! tor con-
trolling
furnace,
oven kiln, immersion heater or to make
flame-start or Arc alarm, B/6 plus 2/6
post and Insurance.
Type "D", We call this the Ice-stat as it cuts in
and out at around freezing point. 2/3 amps. Has
many uses, one of which would be to keep the loft
pipes (rom freezing, if a length of our blanket wire
(IB yds. 10/-) is wound round the pipes. 7/t.
P. A P. 1/1.
Type "E". This is standard refrigerator thermo-
stat. Spindle adjustments cover normal refrigera-
tor temperatures. 7/6 plus 1/- post.
Type "F". Glass encased for controlling the temp,
of liquid— particularly those in glass tanks, vats
or sinks— thermostat Is held (half submerged) by
rubber sucker or wire clip— ideal for nsh tanks-
developers and chemical baths of all types.
Adjustable over range 60'F to 150F. Price 18/-
plui 2/- post and insurance.
Where postage is not definitely stated as an
extra then orders over tt are post free. Below
*3 add 2/9. Semiconductors add 1/- post.
Over 11 post free. S.A.E, with enquiries please.
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369
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TRANSISTOR CHASSIS
5-/6
6 TVantistors, LW/MW, Tele-
seopic Aerial, Brand New.
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(LESS SPEAKERS) P. & P. 4/6.
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£19
STEREOGRAM CABINET
An iltEint 8l»r«o-ram Cabinet
in modern Veneered Mahogany
and cloth covered Front Panel
BLACK LEATHERETTE SIDE PANELS
Dimension' : 52* x I7|" x 1 2*
Speaker positions for Twin
10" x 5" Speakers
OTHER MODELS— SEND FOR LIST
RADIOGRAM CABINETS
ONLY £5.19.6
An attractive discreetly
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TWO SCOOPS FROM "KINGS'
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105/107 DAWES ROAD, FULHAM, S.W.6
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370
Step input. Tuned circuit under-
damped when R is decreased
Fig. S.T. Response of a simulated tuned circuit
Current flow in under-damped
tuned circuit, in response to a
step function
Apply a 2V r.m.s, 50Hz signal to OA1 /Input 2, and
monitor by means of a reliable 10V a.c. meter of not
less than 1 kilohm/volt sensitivity. The input function
should preferably come from a low impedance source
to avoid serious loading errors when the voltmeter is
removed. Next, connect the a.c. voltmeter to the out-
put, of OA1 and adjust CP1 so that OA1 input and
output voltages are exactly equal. CP1 could alterna-
tively be set by the reference voltage and d.c. voltmeter
method mentioned earlier, for a coefficient of 0*1. If
the CP2 setting is altered it will be discovered that the
simulated circuit goes off resonance, and can be tuned
by CP2 between approximately 5Hz and 50Hz.
UNIT "A" will now be ready for analysis of the
Fig. 5.6a tuned circuit, and will also cover a useful
range of other values for L, C, and R in real time.
When handling sinusoidal or step functions, an
amplifier will still have a maximum output voltage
swing of ± 10V, but this will be the peak voltage value.
To check for overloading with an ax. meter, ensure
that amplifier output voltages do not exceed 707V
r.m.s. for a sine wave function, and 5V mean for an
equal mark-space square wave.
RESCALING PROBLEM EXAMPLE 3,
To rescale the problem for larger or smaller values
of L and C, beyond the coverage of CP2, and by
abandoning real time operation, note that a tenfold
increase in tuned circuit frequency corresponds to a
hundredfold increase in 1/LC. For most applications,
where the series resistance R will lie between zero and
just beyond critical damping (R > 2\/[X7C]), the scaling
of RfL can stay as it is for all reasonable values of
L and C, but should anyway only be changed by adjust-
ment of the gain factor at OAI /Input 1 . Similarly, the
/(T)/£ gain of 100 at OAI /Input 2 can remain fixed.
It is not necessary to use inconveniently large or
small input functions when rescaling for new voltages
and currents. 2V r.m.s. could equally well represent an
input function of, say, 02V r.m.s., and from Ohm's
Law the current / will automatically become 2mA,
instead of the former 20mA, even though it is still
represented by 2 computer volts.
If it is desired to extend the computer operating time,
by adjustment of integrator and inverting amplifier
closed- loop gains, refer to Table 5.2, while remembering
that integrator closed-loop gains are calculated on the
basis of 1/RmCi where i? is in ohms and C is in farads.
For reasons of reduced accuracy, it is not advisable
to use computer operating frequencies above 1kHz or
below 005Hz in connection with Problem Example 3.
It should be mentioned that although frequencies in the
region of 005Hz are too low for display on an a.c.
coupled oscilloscope, the behaviour of a system can be
demonstrated in slow motion by the oscillating move-
ment of a d.c. voltmeter pointer (centre-zero).
Some typical oscillograms are given in Fig. 5.7 to
show the response of a simulated tuned circuit. If the
computer oscilloscope is provided with a good graticule,
and has a linear response, amplitude and time measure-
ments which are accurate to within approximately
5 per cent may be obtained straight from the trace.
The behaviour of a real tuned circuit can be evaluated
by comparison with a simulated circuit. A tracing is
made of the real circuit oscilloscope display, and is then
superimposed on the readout given by the simulated
circuit. The computer is adjusted so that time scales
are related by a known factor, and tracing and readout
display are identical, then quantitative measurements
are taken from the computer voltages and dial settings.
Next month: The construction and operation
of UNIT "B"
371
DENTOPHONICS
BY F.R.BERTRAND, BOS.
The term Dentophonics has been applied to the tech-
nique of broadcasting speech from the mouth by the
use of electronics.
Dentophonics works on the same principle as a throat
microphone, where a transducer picks up the sonic energy
transmitted through the tissues as a person speaks.
This is quite distinct to normal microphone techniques
which rely upon air pressure waves.
Dentophonics (DP) is easily demonstrated by the follow-
ing experiment. Plug a sonic probe into the input socket
of an audio amplifier. Press the sonic probe against a
subject's tooth as that subject is speaking, and the voice
of the subject will be clearly heard through the loudspeaker.
TISSUE TRANSMISSION
A sonic probe with a broad surface will pick up sound
from various parts of the head, including the forehead,
temple, cheekbone, and the cheeks themselves. To
obtain good speech reproduction from the cheeks, the
sonic probe has only to be gently pressed against a cheek.
This shows quite clearly that sound is transmitted through
both hard and soft tissues of the body, and it would
therefore be better to drop the term "bone conduction"
and use the term "tissue transmission".
The extent of the tissue transmission of sound is shown
by the following experiment.
A sonic probe was held firmly in a subject's extended
right hand. This sonic probe was connected to the
output of an audio amplifier, and a signal generator was
connected to the input socket of the same amplifier.
The same subject held another sonic probe in his extended
left hand and this second sonic probe was connected to
the input of another amplifier, a loudspeaker being con-
nected to the amplifier output. The subject holding the
probes was in one room, and the loudspeaker was in
another room. When a signal of 1,000Hz was transmitted
through the sonic probe in the subject's right hand, this
signal was picked up by the sonic probe in the subject's
left hand, and was clearly heard by an observer in the
room with the loudspeaker.
BUILT-IN ELECTRONICS
Whilst speech may be picked up by a transducer from
various sites of the head, the mouth offers the most
interesting possibilities, in that there would appear to be
no reason why miniaturised electronic equipment should
not be built-in, at this present time. Already in various
experiments to obtain information on the occlusion of
the teeth, up to six radio transmitters have been "built
into" the mouth.
Any miniaturised electronic equipment designed for
placing in the mouth could be incorporated into bridges
or dentures. The miniaturised equipment could be
designed to be removable, and capable of being switched
on or off.
A dentophonic appliance will have the advantages over
a throat microphone, of being less bulky, and also of
giving better and clearer speech reproduction. A DP
probe will pick up speech from an artificial tooth provided
the artificial tooth is firmly fitted.
The great advantage of dentophonics is the elimination
of background noise. Transducers used for DP are
designed to pick up the transmission of sound in solids,
and should not pick up airborne sound. This means
that the speech of a subject in a high level of background
noise could be heard quite clearly without any inter-
ference by the background noise.
Another advantage of DP is that there will be no need
for the so called "microphone technique" that the public
speaker or performer has to learn.
One objection to DP is that the noise of the teeth
occluding will be picked up; but this objection would
only be valid where a subject has nervous clenching
habits, as normally the teeth mainly occlude during
mastication, the position of rest being with the teeth
slightly apart.
POSSIBLE APPLICATIONS
The applications of DP will be many and varied, but
this technique could certainly be used by the following
persons: outside television and radio commentators,
motor racing drivers, aviators and astronauts, public
speakers, theatrical performers, and deep sea divers.
Where background noise is such that a subject's hearing
may be damaged, the ears could be protected by muffling,
and communication established by using the DP technique.
DP could be used for teaching deaf children to speak,
The DP probe would pick up the sound of the deaf child's
own voice, and even if the child had no hearing whatso-
ever, the child would be able to compare the movement
his or her voice produced with the movement that the
teacher's voice produced.
THROUGH SOLID MASS
Another interesting experiment can be described.
Two audio amplifiers were used, one had a microphone
and a probe connected to it; the other had a DP probe
and a loudspeaker connected to it. A subject spoke into
the microphone, and as he was speaking the probe was
pressed against the wooden casing of the first amplifier,
and the second probe was pressed against the other end
of the wooden casing of the same amplifier. The subject's
voice was clearly heard over the loudspeaker. Thus,
audio sound had been transmitted through a solid and
picked up at the other end.
Perhaps this technique could be applied as a means of
communicating with people who become entrapped in
certain tragedies such as occur in mines or at sea.
Finally, it is apparent that dentophonics in conjunction
with the audiodental technique opens up a new, relatively
untried, but highly promising field of communications.
For Future Reference
An index for volume three (January 1967
# to December 1967) is now available price
Is 6d inclusive of postage.
Easi-binders are available price 14s 6d
9 inclusive of postage. State whether "Vol.
I ", "Vol. 2", "Vol. 3" or-'Vol. 4" is required.
Orders for Binders and Indexes should be
addressed to the Binding Department.
Orders for copies of the Index only should be
addressed to the Post Sales Department, George
Newnes Ltd., Tower House, Southampton
Street, London, W.C.2.
372
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enable assembly in
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PORTABLE CABINET
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standard player £Q If,
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tested with V L8B triode
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ind loudspeaker •'T/O
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Garrard SRF32 18.19.6
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Philips AG1016 Jll.lfl.8
Garrard A70 £14.19.8
Garrard LAB 30 £84.19.8
Garrard 401 £89.19 6
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Better sound! Isolated AC
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Garrard 1000 £8,19.6
BSR Transcription UA.70
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Garrard Stereo Mono
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Garrard AT60 £14.19 6
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Q MAX CHASSIS CUTTERS
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J)0, 14/B Jin. 15/9 liin. 18,'- liin. 80,8 a&in. 37 '9
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PICK-UP ARM Complete with ACOS LF-78 Turnover
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SPEAKER FRET Tyg&n various colours, 52in, wide, from
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EXPANDED METAL Gold or Silver 18 x 18 la B ; -
49/6
99/6
FULL WAVE BRIDGE CHARGER RECTIFIERS ■
8 or 18 T. outputs, 11 amp.. 8/8: 8 a. 11/3; 4 a.. 17.6.
CHARGER TRANSFORMERS. P.&P.5/-. Input 800 850
lor 8 or 12 y„ 1> amai,, 17/6: 2 amps,, 21,'- ; 4 amps.', 30'
MOVING COIL MULTIMETER TK 85.
0-l,000v. A.C./D.C, ohms to 100k. etc.,
SUPERIOR MOVING COIL MULTIMETER
0-2,500*. D.C. 80,000 ohms per volt. 0-l.OOOv, A.C
Ohms to B meg. 60 Mlcroamas. (Full list Meters S.A.E. '
NEW MULLARD TRANSISTORS
OC71 6/-; OC78 6/-; OC81D 6'-; 0C81 6/-; AF115 8/--
AFU4 8/8; 0044 6/-; 0045 6/-; OC171 6.'-; OC170 6/-
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TT45. Push F ul 1 Driver 9 ; 1CT «/-
TT40, Push Pull Output CT 8:1 6-
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TT6B, Output 3 ohmi8Q:l , .,,. si.
TRA1TSI8TOR MAINS ELIMINATORS. FAMOUS "POWER
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DrTTO TRANSFORMER ONLY. SJgeE^:-: l:Vliin....lO:6
WEYRAD PS0 — TRANSISTOR COILS
RA2W 8 in. Ferrite Aerial Spare Cores 6d.
with car aerial coil 12/6 Driver Trans, LFDT4 9'6
O10. P50/1AC 5/4 Printed Circuit. PCAI. ...9/6
I.F,pfiO/8CC 470 kc/s ... 5/7 I.B. Tuning Gang 10/8
3rd I.F, P50/3CC 8/- Weyrad Booklet g/.
Telescopic Chrome Aerials 8in. extends to 23j n . 5/-
Volume Controls
LOUS SPINDLES. MIDGET
SIZE 5 K. ohms to 8 He;:.
LOG or LOT. L/S 3/-. D.P. 67-
STEREO LIS 10/6, D.P. 14/6.
5 g. 8, P. Edge Type 5/-,
80 ohm Coax 8d. yd,
SEMI -AIR SPACED
40yd. 20/-; 60yd. 30-.
FRINGE LOW LOSS I
Ideal BBS lines ■
A
COAXIAL PLUG 1/3, PANEL SOCKETS'1/3. LINE SOCK-
ETS 8/-. OUTLET BOXES, SURFACE OR FLUSH 4/6.
BALANCED TWIN FEEDERS 1,'- yd., 80 or 300 ohms.
CAB AERIAL PLUGS 1/6. SOCKETS 1/3; LINE SOCKETS 2 -
SELMER
TRANSISTOR
AMPLIFIER
QHE WATT
POWER OUTPUT
Portable Cabinet aije 12 X 4
X 8in. fitted 7 X 4ta. Speaker,
Volume Control, Standard
Jack Socket. Uses PP9 Bat-
tery. Will increase to tome and perlormauce
ol Tranalator Radios, Record Players, Tape Recorders, etc.
Ideal tor Guitar practice. OUR lO/i POST
NOTICE
ALL THESE PRICES FIXED TO JUNE 1st, 1968
THE E.A.R. RECORD PLAYER CABINET
Strongly built wooden cabinet covered in Blue and Orey
leatherette size 15 X 17x8 in. Motorboard 14}xl2t in.
ready cut out lor B.3.R. Monarch UA 12/14/15/18/85 decki.
Gilt fittings, strong carrying handle. Amplifier space site 14
X7x3in.il completely en do sed. The baffle board FQ if.
is cot out lora Bi in, dia. speaker. P. St P. 5/8. PRICE 3 ~/ *»
NEW TUBULAR ELECTROLYTICS , |
2/350 v
4/850 T
8/450 t,
16/450 »
38/450 v,
25/25 v.
50/50 v.
100/25 v.
260/85 v. .
500/25 1. .
B-^ 8/450 t.
8^16/460 v.
CAN TYPES
8/600 v 9S
i8'600 t ie/8
16-18,500 ». 7/6
33^38/850 r. 3/8
50-50/350 r. 71-
60 + 100/350 y. 11/6
100^200/275 v.12/6
9 16 + 18/450 v, 4/3
- 32->- 32/350 T. 4/6
SUB-MIN. ELECTEOLYTICS, 1,8.4,5.8,16,85,80,50,100,
850 mid. 15v, 2/-; 500, 1000 mtd. 12v. 3'B 8000 mid. 85v. 9/8.
CERAMIC, 500 v, 1 pF. to 0.01 mid.. 8d. Discs 1/-.
PAPER TUBULARS
350v.-0.1 9d„ 0.5 2'6; 1 mid. 3/-: 2 mfd. 150T, 8'-,
500v. -0.0O1 to 0.05 8d: 0.1 1/-; 0.85 1/8; 0.5 3/-.
l.OOOv.-O.OOi, 0.0083,0.0047. 0.01,0.08, 1/8; 0.047,0.1 2/6.
E.H.T. CONDENSERS. O.OOlmld.. 7kV., 6'6; 20kV., 10/8.
SILVER MICA. Close tolerance (plus or minus i pF.l, 5 to
47 pF.. 1/-: ditto 1°; 50 to 800 pF„ 1/-; 1,000 to 5,000 pF.. 2/-.
TWIN GANG. "0-0" 208 pF. -■■ 176 pF,, 10/8; 385 pF„ minia-
ture 10/-: 500 pF. standard with trimmers, 9/6; SOOpF.
midget less trimmers, 7/6; 500 pF. Blow motion, standard »/-;
small 3-cang 500 pF. 1B/B. Single "0" 385 pF. 7/8. Twin 10/-,
SHORT WAVE. Single 10 pF., 25 pF., 50 pF„ 75 pF.,
100 pF., 180 pF., 5 6 each. Can be ganged. Couplers 9d. each.
TUNING. Solid dielectric. lOOpF., 300pF.,500pF.. 5/- each.
TRIMMERS, Compression ceramic 30. 50, 70 pF., 9d.;
100 pF„ 150 pF., 1,3; 250 pF„ 1,6; 600 pF., 750 pF„ 1/9 .
250 v. RECTIFIERS. Selenium 1 wave 100mA 5,'-: BY10O 10 -.
CONTACT COOLED i wave 60mA 7/6 ; B5mA 9/8.
Full wave 75mA 10*. ; 150mA. 19/6 j T.V. rests, Irom 10,'-.
'S0N0C0L0R' CINE RECORDING TAPE
5* reel. B00' LP with strobe markings also cine light de-
flector-mirror lor synchronisation. Suitable 1 J 1
all tape recorders and cine projectors. List 28.- 11; - each
NEW B.A.S.F. LIBRARY BOXED TAPE
Tin. L.P. i, 800 ft. 45 -; 7 in. D.P. 2.400 ft. 70 -
60 min. Cassette C60 (For Philips, etc.) 17/6
Spare Spools 2/6. Tape Splicer 5/-. Leader Tape 4/6.
REUTER Tape Heads lor Collaro models 8 track 81/- pair.
MAINS TRANSFORMERS
Post
/- each
850-0-350 80 mA, 6.3 v, 3.5 a. 8.3 v. 1 a, or 5 T. 2 a. 80/-
350-0-350 80 mA. 6.3 v. 3.5 a. 8.3 v. 1 a, or 5 v. 8 a. 35'-
MT. 5I0'3OO-O-30O v. 120 mA.. 6,3 v. 4 a, 6.3 v, 2 a. 457-
MINIATORE £00 v. 20 mA., II.3t.1i 12/8
MIDGET 820 v. 45 mA., 6.3 T. 8 a. 17/6
HEATER TRANS. 6.3 v. U a., 8/6; 6.3 v. 4 a 12/6
Ditto tapped sec. 1.4 v., 2, 3, 4, 5, 8.3 v. I! amp. . . 18/6
GENERAL PURPOSE LOW VOLTAGE, Outputs 3, 4, 5,
6, 8, 9, 10, 12, 15, 18. 84 and 30 v. at 2 a 30/-
1 amp., 8, 8, 10. 12, 16, 18, 20. 24, 30, 36, 40, 49, BO, 35/-
AUTO TRANSFORMERS 0-115-230 v. Inpnt Output,
80w. 18 6: 150W.30/.; 500w. 926; lOOOw. 175'-.
CRYSTAL MIKE INSERTS
l: :: tin. 68; ACOS 1} - iin. 8.6, BM3, 1' dia. 9/6
MOVmo COIL MIKE with Remote Control Switch 19/8
ALL PURPOSE HEADPHONES
H.R. HEADPHONES 2000 ohms 19/6
H.R. HEADPHONES 2000 ohms Super Quality 36/'
LOW RESISTANCE HEADPHONES 3-5 ohms 35/>
1968
ORAM
CHASSIS
Post 5/-
Tbree Waveba nds : F i v e V a 1 v es : EC H S 1 . EF88 .
Long., Med., Short. Gram. EBC81, EL84, EZ80,
12-month guarantee. A.C. 200-250 v. Ferrite Aerial
5 waits 3 ohm. Chassis 13 tin. :■ Tin. X Sin. dial size
18in y 4in, Two pilot Lamps. Fonr Knobs. /If) 10
Aligned calibrated. Chassis isolated Irom mains •" ■ V. I T
DE LUXE STEREO GRAM CHASSIS V.H.F., MW, SW
19-50m, SW 60-lS0m. Magio eye, push buttons,/ 10 10
8 valve plus rect. Size 15' at "'." 1 6' high fc I F. I F
VEROBOARD 0.15 MATRIX
8/ :■" 5iu. 3/8d. 8! X 3Jin. 5/8d. 32 x 3;in. 3,'Bd.
EDGE CONNECTORS 16 way 4/-: 24 war 6/-.
PINS 38 per packet 3/4d. FACE CUTTERS 7/6.
S.R.B.P. Board 015 MATRIX 8: in, wide 6d. per lin; 3 iin.
wide 8d. per lin; 5in. wide 1'- per lin. (up to lTin.
BLANK ALUMINIUM CHASSIS. 18 t.w.g. 2! in. aides,
7x4in.. 5'6; 9x Tin.. 6/8: llx3in. 6/6; llx7in. 7/8;
13 x Bin. 9 6; 14*1110. 12/8; 15 <14ia.. 15/-.
ALUMINIUM PANELS 18 s.w.e. 18xl2in. 8/6; 14 - Bin.
5/8; 12 x Bin. 4/8; 10>i 7in. 3/6; SxBin. 2/6; 6>:4itt. 1/6.
THE INSTANT
BULK TAPE
ERASER AND
RECORDING HEA
DEMAGNETISE
800/250 t. A.C
Leaflet S. A.E,
CANCELLED EXPORT
SHIPMENT
15 BAKER
WOOFERS
80-10,000 eps. Bass
Resonance 18-25 eps.
Massive Ceramic
Feirobar Magnet.
Flu density 15,000
lines. Rated 20 watts.
15 ohms. Overall depth
only 61in. Weight 15 lbs
OUR C11 1Q C Carriage, packing
PRICE *l lil «7iO and insnranee 10/6,
"BONDACOUST " Cabinet Wadding 18in. wide 2/6 loot,
BAKER GROUP SPEAKERS— ^J
'Group 25' 'Group 35' 'Group 50'
Jf»-.5gns. ^w a :Hgns. ^; I8gns.
E.M.I. CONE TWEETERS 3J.in. Bfluare. 3-80kc/i. lOw. 17/8.
Smtlity Horn Tweeters 8-18kc/s. lOw. £9/6. Crossover 18/6-
LOUDSPEAKERS P.M. 3 OHMS. 2iin„ 3in.. 4in.. 5in..
7in. X 4in„ 15/6 each; Sin. 22/6; 6 J in. 18/6; lOio. 80/-;
18in. double cone 3 or 15 ohm 35.-; 10 X Bin. 30/-; 8 X Sin. 21/.;
E.H.I. Doable Cone 13J x Sin., 3 Of 15 ohm models, 45/-.
SPECIAL OFFER! 8 ohm. 21io„ 5in,; SO ohm. 2iin.. 2jia.
I C if. 25 ohm. 6in., 6x4in.; 35 ohm. 3in.,5in., 7 x din.
1 J /° EACH TYPE. 16ohm.3in„7 ^5in.,10 X BJin.
JACK SOCKETS Std. open-circuit 8/6. closed circuit 4/6.
Chrome Lead Socket 7/8. DIN 3-pin 1/3, 5-pin 1'6; Lead 3/6,
Phono Plugs 1/-, Socket 1/-. JACK PLUGSStd. Chrome 8/-;
2.6mm.; 8.5mm. 1/8; DIN 3-pin 3/6: 5-pin 5/-.
WAVE-CHANGE SWITCHES WITH LOHG SPINDLES.
3 p. 2- way, or 8 p. 6-way, or 3 p. 4-way 4/6 each.
1 p. 18-way, or 4 p. 8-way, or 4 p. 3-way, 4/8 each.
Wavechmnge " MAKTTS " 1 p. 18-way, 8 p. 6-way, 3 p. 4-way,
4 p. 3-way, 6 p. 2-way, Prices inclnde click spindles, adjustable
stops, spaces, ete„ 1 water, 10/6; 8 water, 15/-; 3 water, 18/8.
TOPPLE SWITCHES, sp. 2/6; sp. dt. 8/6; dp. 3/6: dp. dt. 4/6,
ALL EAGLE PRODU CTS
79/6
EAGLE AM TUNER. Medium Wave.
Transitto rSuperhei. Ferriteaerial.e tc.
EAGLE DE LUXE TAPE SPLICER Cuts, trims, I fit,
joins tor e diting and repaira. With 3 bla des. I */v
EAGLE 4 CHANNEL TRANSISTOR MIXER. Add
musical highlights and sound effects to recordings. Will
mix Microphone, records, tape and tuner with
separate controls into single output.
EAOLE DVSAMIC MICROPHONE. Impe- /£ IZ #,
dance 600 ohm/50K. 70-12,000 ops. Universal ***• I Q.U
mounting , stick, hand or stand. Prolesgiona l qaality,
Siz Transistor. Ready
Calibrated slide dial £Q Inn
EAGLE FM TUNER 88-108 Mc
built. Printed Circuit,
toning. Size 6" x 4'
EAGLE 3 WATT AMPLIFIER. 4 Transistor Z Q If.
Push-pull Ready built, with volume control OF/ a
40- PAGE EAGLE CATALOGUE St- Post Free
■k RADIO BOOKS -k (Postage 3d.)
High Fidelity 6 peaker Enclos ore a a nd Plant 5/-
Traosistor Snperhet Commercial Receivers 7/6
Mullard Audio Amplifier Manual 8/6
Radio Valve Guide, Books 1, 2, 3, or G each 5/-
Practical Radio Inside Out.. 4/6
Transistor Audio Amplifier Manual Book 1, 3/6 ; Book 2, 6/-
Shortwave Transistor Receivers 5/-
Traniistor Communication Set! 6/-
International Radio Stations List 2/0
Modern Transistor Circuits for Beginners 7/6
Sub-Miniature Transistor Receivers 57-
Wirele is World Radio Valve Data 9/S
At a glance valve equivalents... 6/»
Tarvel. Transistors. Diodes equivalents manual ,10/6
Worth Doable! PRICE
RETURN OF POST DESPATCH Minimum P«t and Packing ehorgeTi/6,
RADIO COMPONENT SPECIALISTS
RESISTORS. Prelerred values, 10 ohms to 10 meg.
i w., i w., 1 w., 20% 3d.; li w. 8d,; 2 w. 1/-; * w, 10% Id.
HIGH STABILITY. I w. 1% 10 ohms to 10 meg., 2/-.
Ditto 5%. Prelerred values 10 ohms to 22 meg,,8d.
5 watt -) 0.5 to 8.2 ohm 8 w, f 1/6
10 watt > WLRE-WOUND RESISTORS < 1/B
15 watt J 10 ohms to 6.800 obras L 2 -
10K, 15K, 80K, 85K, 68K, 10W. «/-
WIRE-WODND 3-WATT WIRE-WOUKD 4-WATT
POTS. T.V. Type. Valnes STANDARD SIZE POTS.
10 ohms to 30 K., 3/3, LONG SPINDLE VALUES
Carbon 30 K, to 8 meg., 3/-. ■ 60 OHMS to 100 K„ 7/8,
VALVE HOLDERS. MOULDED Sd; CERAMIC 1'- EACH.
SCREEB1WO CAW3 1.'-; VALVE BASE PLUGS T 8i3.
SANGAMO 3 inch SCALE METERS 45/- e a.
Virions calibrations and movements. 100 Microsmp;
1 MilUamp 50-0-50 Microamps, etc.,, S.A.E. lor Hit.
BRAND NEW QUALITY
EXTENSION LOUDSPEAKER
Black plastic cabinet, 20ft. lead and
adaptors. For any radio, intercom, tape
recorder, etc. 3 to 15 ohm. POST JQ /
Size:
i' I Si' i 3'
C.O.D. Sj. extrc. Full List //-. CALLERS WELCOME
337 WHITEH0RSE ROAD, WEST CROYDON
Written guarantee with every purchase. (Export; Sencf remittance and extra postage, no C.O.D.) Buses 133, 68 pass door.S.R. Sin. Seihurst. Til. 01-6384-18(5
373
4 STATION INTERCOM
SoItc your communica-
tion problems with tais
*-SUrton Trumitor Intercom system (1 matter ami
8 Sabii, in de-luxe pl.ieitc cabinets [or desk at wall
mounting. Call/talk/lletcn Irom Muter tn Suit ami
Sub! to Hsiter, Meal lj- suitable (or Business, Sur-
gery, Schools, Hospital, Office and Home. Operates
on one 9V battery. On/oft switch. Volume control.
Complete with 3 connecting wires curb fiOIt. ami
other accessories. P. & F. 7/G,
WIRELESS INTERCOM
Ho batteries — no wi«r. Just plug in tlw maius lur
instant two-way, loud and clear
On.'ofl switch and volume control.
T. & r. 7/0 extra,
If!
Same a« 4-Station Intercom lor two-way instant
communication. Ideal as Bahy Alarm asd. Uoor
Phone. Complete with 06ft, connecting wire. Battery
2(8. P. & P. 3/6. -
map
59/6
'Why not boost
business effi-
cieucy with this incredible De-Luxe Telephone Ampli-
fler. Take down long telephone messages or converse
without holding the handset. A uselul office aid. On/
oft switch. Volume control. Battery 2/0 extra. P. & P.
2/6. Full price refunded it not satisfied In 7 days.
WEST LOrTDOH DIRECT SUPPLIES (P/E5)
169 KEHSraGTOrf HIGH STREET, LONDOJT. W.S
CRESCENT RADIO LTD.
(electronic component specialists)
For all regular components try
40 Mayes Road, Wood Green, N.22
For surplus components
and equipment try
1 1 Mayes Road, Wood Green, N.22
BARGAIN BOARD NO. I
7in x Sin board with the following compo-
nent) attached:
2 GET872A transistors
2 Mullard OA 10 diodes
2 Mullard OA5 diodes
(2 Midget iW Resistors various values
8 Midget Capacitors various values
Including postage in Great Britain 4/- each
BARGAIN BOARD NO. 2
Siin -, 4in printed board with the following
long lead components: 20 diodes, including
Mullard OA73 and OA86; 12 5% jW resistors.
Including postage in G.B. 3 - each
TRANSISTORS AND DIODES
2/6 each
5/6 each
5/- each
5/- each
2/6 each
3/6 each
4/- the pair
1/6 each
2/6 each
AAI20
BYI05
ACI67
ACI6S
2N397
2NI308
Matched 2G37BB and 2G339B
2G339A
2G40I
SPECIAL LINES
Power transistor heat sinks 7tn X 2lr> I/- each
Double transistor copper cooling clips 9d each
2jin transistor speaker, B0 ohms 5/6 each
Double pole rotary ON/OFF mains switch
2/- each
On one bracket 2-500WQ pre set pots plus
! D.P, rocker mains switch, 1/9
250k(l pre set pot linear I/- each
Midget Skll pot with D.P. switch 2/6 each
PRINTED CIRCUIT BOARD
9±in .-: Bin 2/6 each
Bin x Sin I /I I each
I2in v. 3in 1/3 each
A. M. RADIO TUNER
2 valve Medium and Long Wave tuner with
power supply, will give good reception through
any amplifier. Price on this item includes
Postage and Packing, tA. 0. 0.
PLEASE INCLUDE POSTAGE WITH
NEW RANGE BBC 2 AERIALS
AU U.H.F. aerials now fitted with tilting bracket
and 4 element grid reflectors,
JjOtt Mounting Arrays, 7 element, $71*.
11 element, 45/-. 14 element, S2/6. 13 element,
«/-. Wall Mounting; with Cranked Arm,
7 element, «0/-. 11 element, 87/-. 14 element,
75/-. 18 element, 83/6. Mast Mounting with
2ln. clamp. 7 element, 42/8; 11 element, 55/-;
14 element, 62/-; 18 element, 70/-. Chimney
Mounting- Arrays, Complete, 7 element,
72/6; 11 element, 80,'-; 14 element, B7/6;18 element,
«/-. Complete assembly Instructions with every
unit. :Low Loss Cable, 1/8 yd. U.H.F. Pre-
amps from 75/-. State clearly channel number
required on all orders.
BBC • ITV AERIALS
BBC CBaad 1). Telescopic
loft, 3*/-. External S/D, »/-.
"H", £2.15.0.
ITV (Band 3). 3 element loft
array, 30/-. 5 element, 410/-.
7 element, 50/-, Wall mounting,
3 element, 47/6. 5 element. 52/6.
Combined BBC/ITV. Loft
1+3, 49/-; 1 + 5, 50/-; 1+7,
60/-: Wall mounting 1+3, 57/6;
1+5, 67/6; Cnlmney 1+3. 67/6;
1+5,75/-.
VHF transistor pre-amps,
75/-.
COMBINED BBC1— ITV— BBC2 AERIALS
1+3+9. 70/. 1+5+9, 8*-/. 1+5 + 14, It/-.
1+7+14, 100/-. Loft mounting only. Special
leaflet available.
F.M. (Band 2>. Loft S/D, IS/-, "H", 32/6, 3
element, 55/-. External units available. Co-ax.
cable, 8d. yd. Co-ax. plugs, 1/4. Outlet boxes, 5/-.
Dlplexer Crossover Boxes, 13/6. C.W.O. or CO.D.
P. & P. 5/-. Send 6d. stamps for Illustrated lists.
CALLERS WELCOME
OPEN ALL DAY SATURDAY
K.V.A. ELECTRONICS (Dept. P.E.)
27 Central Parade, New Addinaton
Surrey— CRO-O J B
LODGE HILL 2266
J
p\-'*i3^'
HOME RADIO (MITCHAM) LTD. Dept. PE, 187 London Road, Mitcham, Surrey, CR4 2YQ Phone 01-648 3262
CAPACITORS, Hon Electrolytic
CAPACITORS, El
(ctrolytic
Lilt No.
Opacity
Voltage
Price
1SGI
1.500mF
50V
6/-
IBG2
SDOmF
25V
4/-
IBG3
500mF
12V
V-
IBG4
lOOmF
50V
2/6
IBGS
32m F
45QV
4/6
IBG6
32mF
350V
%
IBG7
BmF
500V
m
Liit No.
Capacity
Voltage
Price
IBGil
4mF
600V
67-
IBGI2
2mF
BOOV
47-
IBGI3
2mF
600V
4/-
IBGH
2mF
500V
1/6
IBGI5
ImF
600V
>/-
Capacitor Pack I BG 17
Capacitor Pack containing Silver Mica, Moulded Mica and paper condensers. Silver Mica
values 15,25,65,71,80, 160,200.240,330,470, 1,000, 1,500, 1,670,4,000 (the470pFare
750V.) 12 out of the above 14 are included in this pack. Moulded Mica values 68,
820. 1,000, 0-002, 0-005. 0"0I . (The P 002 are 2,250 Volts Test.) Five out of the above
six are included in this pack, plus one 002 paper 750V and 0'lmF Plastiseat 750V.
Price 3/6
CAPACITORS, TUNING
Lilt No. Capacity Gangs Notes
IBGIS lOpF
Air Tune
lacks on
IBGI9 10-IOpF
1BG20 !76 + l76pF
l+xli
F.M.)
3/6
46
1 I+X
(Ideal
1 With screen
and trimmers
lft + l* + l 6/-
CAPACITORS, TRIMMING
Lilt No. Capacity Notes Price
IBG22 IOOO + 300pF Compression 2/-
IBG23 50 + 50x50 1-
S0+50pF
Compression 2/—
CAR SUPPRESSORS
I BG26A Car Plug Suppressor* 4 for 4/6
Every year we acquire a number of exceptional bargains which
we offer first of all to the purchasers of our Catalogue, in the
form of a special bargain list. To give you a taste of these
tempting bargains we reproduce a part of the list here.
The rest of the list consists of many other most interesting bargain
items — Diodes, Neon Lamps, Switches, Transformers, Valves,
etc. We can supply the complete list for a shilling, but better
still, why not buy our 1968 Catalogue and get the list free. The
Home Radio Catalogue is acknowledged as one of the finest
electronic components catalogue available today — its 256 pages
list over 7,000 items, more than 1,300 of them illustrated. And
with the catalogue, in addition to the bargain list, you get five
vouchers, each worth a shilling when used as directed, a voucher
worth another five shillings if used to purchase a Weller Soldering
Iron, an order form and an addressed envelope. All this for 9/6!
(7/6 plus 2/- P. & P.). Why wait?
Send your cheque or P. O. with
this coupon today!
Phase write your Name and Address in block capitals
NAME.
! ADDRESS.
1 HOME RADIO LTD., Dept. PE, 107 London Road, rttttham, CM 2YQ j
374
MODIFICATION FOR PRE- HEATING
THE LAMP ELECTRODES
We have been advised by a well known lamp manu-
facturer that the 6W 9in lamp employed in the
Fluorescent Camping Light (March 1968) is designed to be
used only in circuits which arrange to pre-heat the lamp
electrodes either before, or simultaneously with, the
application of a pulse or steady state voltage across the
lamp in order to start it.
It is explained that the practice of cold starting, as in our
published design, can result in very heavy lamp end
blackening, and a very short lamp life.
We are therefore publishing an alternative circuit by
R. B. Hayle which incorporates a pre-heat facility.
In the modified circuit Fig. 1 the "low" output switch
position is omitted, and a three- pole switch is used in place
of the two-pole switch specified in the original circuit. This
enables the electrodes to be energised via R4, which should
be selected so that, with a 12V supply battery, the pre-
heating current is not less than 160mA.
Under these conditions, switch SI should be held in
position 2 (pre-heat) for at least one second before going
over to position 3. Capacitor C2 is permanently connected
to CI, Rl, R2, and Tl. The switch is now used entirely
for preheating and running. The amount of rewiring in-
volved is not great, and readers will be able to convert their
Camping Lights with little difficulty.
A modified wiring diagram
of SI is shown here in Fig. 2,
Similarly modified versions
of the main unit wiring are
shown in Fig, 3.
The pot-core assembly LAS
can be obtained from retail
outlets of Milliard com-
ponents including Henry's
Radio Ltd. whose address is
on the back cover.
The author does not advise
the circuit to be converted
for a 6 volt battery supply.
The saturation voltage across
the transistor becomes a sig-
nificant factor and leads to
reduced efficiency. A 6V
version would have lead to
undesirable circuit complica-
tions.
Fig. 3. Top and underside
views of the electronics in-
cluding the modified wiring
details
Switdi pottUom 1-OFF
2-PftEHEAT MQ-J50ml"
_. , 3-START 440mA
Fig. *. Modified circuit diagram. An extra resistor R4 Is
needed
r«d orwn LMd5 „((„
TogA TogF onn ToflE
Fig. 2. New wiring details of SI. Resistor R4 is 4 7 LI 3W
wirewound
375
nA
A SELECTION FROM OUR POSTBAG
Traffic delay
Sir — I am interested in the mechanical
delay system employed in car rever-
beration units that I have seen and
heard on recent visits to the U.S.
Radiomobile have done some
research but have since dropped the
idea as they feel there is insufficient
interest over here (or so they say).
One problem appears to be the
harder springing of U.K. vehicles
than that found on U.S. cars, however,
1 hear there is even one delay system
now that allows the car to be driven
off the curb without vibration to the
unit.
I am told that the spring (or
whatever) assembly should be
mounted along the car axis and not
across it.
I am not deterred by hard springing
and am keen to build one and use it in
conjunction with my car radio, and
do not see the electronics posing too
much of a problem.
I am advised that a 2 watt output
from the echo amplifier would be
sufficient against the 8 watt output
of my radio. Control of echo is
normally done from a potentiometer
mounted under the dashboard.
A speaker mounted on the back
shelf (if possible) alongside the main
speaker makes the sound appear to
be 100ft behind you. A marvellous
sensation for relaxing in heavy
traffic.
In conclusion, I should appreciate
any information you or any readers
could give me as to the best drive,
pick-up units (to avoid microphony)
and the best suspension to avoid
rattle.
M. C. Bell,
Henley-on-Thames.
Any suggestions ?
Cranky?
Sir— Whilst this magazine publishes
many interesting and useful projects
it sometimes contains circuits which
are complicated when compared with
the function they are intended to
perform. I feel that there is a real
danger of using electronics simply for
the sake of using them. This could
easily detract from the useful purpose
of the magazine and the good
standing of electronic experimenters.
Any person using a complicated
circuit to perform a simple function
must be regarded as a "crank". For
Impact Counter (March 1968) with
a transducer, Schmitt trigger, twenty
resistors, eleven capacitors, seven
transistors, five diodes, etcetera, why
not connect the electro-mechanical
counter to a pair of contacts and a
battery? The contacts may wear
but the saving on the other compon-
ents would more than pay for them.
As for the steam presence alarm, same
issue, dare I suggest a whistling
kettle?
F. Crimmins,
Folkestone, Kent.
IMPACT COUNTER. To answer this
criticism, it is necessary to explain the
particular problem this device was
designed to cope with,
The originat purpose of the impact
counter was to count small neon lamps,
which weigh J$oz. The contacts must
not close more than once per neon, and
must always close whether the neon wire
leads are upwards or downwards. It is
not possible to use anything but a very
open funnel as the neons tend to bridge.
The closure time must be long enough for
the counter to operate properly, therefore
the monostable pulse is adjusted so that
it allows the neon to bounce inside the
pulse length.
For industrial use reliability and ease
of replacement are important. This
circuit divides readily into four parts
which can be tested independently.
STEAM PRESENCE ALARM. You can
certainty suggest a whistling kettle, but
it would be no use to a deaf person, or if
you are out in the garden. The simple
sensor can be used with an electronic
relay to operate an audible alarm, or even
to switch off the stove if you wish.
May we suggest these are two good
examples of electronics being used
practically?
What's in the box?
Sir — I was very interested by C. F.
Weir's article in the February issue
of P.E. on Cine and Tape Sync. His
suggestion at the end for an all-elect-
ronic version prompted some thinking
on my part because I possess a similar
cine system to that of Mr Weir, but
in 8mm.
It occurred to me that a 1 6 frame/sec
projection has each frame flashed
three times on the screen to avoid
flicker, this being done by a rotating
disc with three sectors in the optical
projection system. Thus the screen
picture flashes 48 times per second.
If the projection rate is increased
to 16i frames/sec, then the picture
flashes become 50 per sec. This
could be synchronised with a 50Hz
signal from the second track of a
tape recorder, if the flashes are
detected by a light sensitive resistor.
At this point I am stumped, because
the next step is to convert any error
in the two frequencies into a signal
which will fire an s.c.r. in the power
leads to the projector. The problem
is set in the following diagram.
Could any readers possibly suggest
a circuit for the black box?
The tape recorder need not be a
full stereo type, but it should be four
track with leads to the head winding
which is not actually playing the
sound track. This is the case with
many Philips/Cossor/Stella machines
which are mono with a stereo outlet
socket. If the model is transistorised,
then the same socket could provide
power for the "black box", since a
few milliamps at about — 20V are
available. Two-track machines could
have a third head mounted to scan
the lower track, which should be pre-
recorded, when the upper track is
recorded with 50Hz from a step-down
mains transformer.
It is important to note that the
s.c.r. will only control an a.c./d.c.
type motor, and the control should
never feed a transformer which is used
to power a low voltage projector bulb.
D. Watts,
Lincoln.
Series of talks
Sir — Your Sussex readers may be
interested in the following announce-
ment, which will shortly be locally
advertised :
"A series of six talks and de-
monstrations on High Fidelity,
Stereo and Sound production will
be given weekly at the Portland
Further Education Centre, 1 1 Port-
land Road, Hove, on Wednesdays,
commencing 24th April, 1968.
Evenings from 7.0-9.0 p.m.
Further details may be obtained
from the Principal for Further
Education at 62 St Leonards
Gardens, Hove, Sussex."
376
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COMPLETELY SAFE ANO A [' PROVED. Brand
netr and rcadv t.i use improved de-luxe model. Price
M 10, i arrhigc and insurance 10, -. C.O.0. 11 required.
Discount itlvcli In Schools, Universities and Research
EataMMmirntc, Free demonstration at our prcmlws.
Dent. F.E.U
MISCELLANEOUS
(continued)
MzamsMHMm
24 C A WOODS YARD, MILL STREET
LEEDS ■ TEL. LEEDS 25593
Cillers weleome
MISCELLANEOUS
CALL OR SEND for list from the most Interest-
inti sliti|> iit LiitUMishire. KJpftrical Mech-
anic-ill and Electronic Goods. JtOGKKS. :ii
Xelsou Sirt-it, Smithport.
"PRACTICAL ELECTRONICS" Rhythmic
Effects Unit, Itnpact Counter. Fluorescent
Camping Light. Giissandavibe. Spring Line
Reverberation Unit. I.e. Tape Recorder.
UombotrOB. Analogue Computer, Photo-
graphic Exposure Meter. Water Level Alarm.
i>'u/,/. Hox. Yodeller Door Monitor. Marmonit!
Distortion Meter. IX. Oram Amplifier.
Thyristor l'ower Controller. Trttnsbtor
Millivolt meter. Screen wiper Delay Unit.
Investigator Oscilloscope. C.R.O. Trace
lii pi idler. Light Operated Stopwatch.
Proximity Detector. Photoflash Slave Unit.
Integrated Stereo Amplifier, and all construc-
tional projects going hack to Issue 1. -Send
s.a.e. for vour choice of itemised price lists.
AJAX ELECTRONICS, 18a llumhold Road,
Fuiham, London, S.W.6.
1 GANG SOOpF TUNING CAPACITORS
New and boxed 7 6 post paid
BIG BARGAIN PARCEL
Capacitors, resistors some high stab, rectifiers,
potentiometers, diodes, transistors, connecting
wire, ere, only 10- post paid.
S.A.E. for (ill J of other bargains
SALOP ELECTRONICS
9a GreyTriars Road, Colehim, Shrewsbury, Salop
BOOKS AND PUBLICATIONS
SURPLUS HANDBOOKS
19 set Circuit, and Notes 5/6 P.P. fid
1 155 set Circuit and Notes .... 5/6 P.P. 6d
H.R.O. Technical Instructions . . 4/6 P.P. fid
38 set Technical Instructions 4/6 P.P. fid
46 set Working Instructions. . , , 4/6 P.P. fid
88 set Technical Instructions . .. - 6,'- P.P. fid
BC. 221 Circuit and Notes 4/6 P.P. fid
Wavemeter Class DTech, Inscr 4/* P.P. fid
18 set Circuit and Notes 4/6 P.P. 6d
BC. 1 000 (31 set) Circuit & Notes 4/6 P.P. fid
CR.I00 B.28 Circuit and Notes 9/6 P.P. 9d
R.I07 Circuit and Notes 6/- P.P. fid
A.R.88D. Instruction Manual 16/- P.P. 1/6
62 set Circuit and Notes 5/6 P.P fid
52 set Sender& Receiver Circuits 7/6. post free
Circuit Diagrams 4/- each post free.
R.lllfi/A, R.I224/A, R.I3SS. R.F. 24, 25, & 26,
A, 1134, T.I 154, CR.300. BC.342. BC.3I2.
BC.348.J.E.M.P. BC.624. 22 set.
Resistor colour code indicator, %l- P.P. fid.
S.A.E. with ail enquiries please.
Postage rates apply to U.K. only.
Mail order only to j
instructional Handbook Supplies
Dept. P.E., Talbot House, 28 Talbot Gardens
Leeds 8
RECEIVERS AND COMPONENTS
BARGAIN PARCELS of new surplus Elec-
tronic Components, 2/6, 6/-, TO/-, post free.
DOLPHIX ELECTRO NMCS, n Pooles Way,
Briar Close, Durntwood, nr. Lichfield.
COMPUTER PANELS
Eight assorted printed
circuit panels with tran-
sistors, diodes, resistors,
capacitors, etc. Guaran-
teed minimum . 30
transistors. Ideal for
Experimenters. 8 boards
10/-. POST FREE.
Trade ond Bulfc enquiries
welcome.
I SO0 + 2000 MFD Electro-
lytes 25 volt DC wke,
3/- each. 9d. P. & P.
KEYTR0NICS, 52 Earls Court Road,
London, W.8, Mail order only
RECEIVERS AND COMPONENTS
(continued)
REPANCO Transistor Coils and Transformer.
for tlie Constructor. Send stamp for lists
RADIO EXPERIMENTAL PRODUCTS
LTD., !W Much Park Street, Coventry.
MICROMINIATURE MICROPHONES
Sensitive dynamic type. Will pick-
up rustle of newspaper from 30 feet.
Size 9 mm. X 9 mm. X 3S mm.
Impedance I Kfl.
ONLY SB/ft
Post frtt — CvV.O.
MICRO DATA SYSTEMS
30 BAKER ST., LONDON, W.I
DUXF0RD ELECTRONICS (PE)
DUX FORD, CAMBS.
C.W.O, P. & P. I/-. Minimum order value 5/-.
(Trade inquiries invited)
CAPACITORS (Tubular, Axial Lead*):
Electrolytic (Mullard): -10% to +50%.
4V: BuF, 32pF, 64uf, ITSuF, 2SQnf. 400uF.
S-4V: 6-4nF, 2SfiF. SO^F, IOOmF, 200; t F, 320^F.
10V: 4*tF, IfifiF, 32/iF, 64uF, I25uF. 200liF.
16V: 2 5/iF. lOjiF, 20(tF, 40nF, BOuF, llS^tF.
25V: |-6 M F. 6-4^F, 13-5^F, 2S/iF, SOuF, BOjiF.
40 V: IjjF, 4uF, 8uF, I6^F. 32>jF. 50uF.
♦4V; 0-64mF. 2-SmF, SkF. lOuF, 20fiF, 31mF.
All values 1 .3 each.
Polyester (Mullard): -10%.
160V: 001 uF. OOISijF, 0022uF, 6d. 0033(uF,
0047fiF, 76. 0068aiF, OluF. 8d. OlS^F. tOd,
0-22aF, ltd. 0-33^F, 1/2. 47^F, 1/5, 0-6BuF,
2/1. I jjF, 1,6.
400V: 0001 uF, OOOISjuF, 0-0022/iF. 00O33mF,
00O47(iF. 00068/iF, OOlfiF, 6d. 0015/iF, 0022^F.
7d, 0033fiF, 8d. 0047mF, 068fjF, 9d. 0'lnF,
lOd. ISuF, 1/1. 0-22mF. I/S. 33»iF, 2/1.
0-47nF, 2/6.
Polystyrene: =5%. 160V: 5pF, lOpF, !5pF.
I2pF. 33pF. 47pF. S6pF, 6BpF, lOOpF, !50pF, 2I0pF,
330pF, 470pF. 680pF, 820pF, 5d. I ,O00pF, I .SOOpF,
2,200pF. 6d. 3,300pF, 4.700pF, 5.600pF, 7d.
ID.OOOpF, Bd. IS.OOOpF, 22,0OOpF, 9d,
POTENTIOMETERS (Carbon): Long life, low
noise. iW at 70°C. -20%£iM, !■ 30% > JrM.
Body dia., Jin. Spindle, lin x iin. 2;- each.
Linear : 100, 250, 500 ohms, etc., per decade to
I0M. Logarithm. c; 5k, I0k, 25k, etc.. per decade
to 5M.
SKELETON PRE-SET POTENTIOMETERS
(Carbon): Linear: 100, 250. 500 ohms, etc., per
decade to 5M.
Miniature: Q-3W at 70°C. 4:20% ^iM, ±30%
> ±M. Horizontal (0-7in x 0-4in P. CM.) or Ver-
tical (0-4in x 0-2in P. C.M.I mounting, I/- each,
Submin. 0IW ar 70°C. ±20% SIM, -J: 30°/ ? >
IM. Horizontal (0-4in X 0-2tn P. CM.) or Vertical
(0-2in x lin P.C.M.) mounting, lOd. each.
RESISTORS (Carbon fltm): Hiah nihility, very
low noise. jW it 70*C. Body 4 in x iin. Value* in
each decade: 10, 1 1, 12, 13, IS, 16. I B, 20. 22. 24, 27,
30. 33, 36, 39, 43, 47. 51. 56. 62. 68, l.S. 82. SI from
4 70 to IM. =5%, 2d each. 1-2M. I-5M. I -8M.
2-2M, 2-7M. 3-3M, 3-9M. 4-7M, 5 6M, 6-BM, 8-2M,
I0M. i 10%, Id. each.
SEMI-CONDUCTORS (All new): OA5. OABI,
1/6. OC44. OC45, 1/9. OC7I, OC72, OC73,
OC6I, OC81D, OCS2D, OCI70, OCI71, 2/1.
OCI40, AFM5, AFII6, AFH7, 3/-.
SILICON RECTIFIERS: 5A at 70°C. 400
P.I.V,, 3/-. 800 P.I.V., 3/3. 1,250 P.I.V., 1/9.
1,500 P.I.V.,4/-.
SEND S.A.E. FOR JANUARY I96B
CATALOGUE
OC22 B/- OC84
4,6
AFZI2
5 6
BYZI0
»/6
NKT674
6/-
RECORDS
OC23 B/-
OC24 B/-
0070
OCI7I
4/-
4 -
BCY33
BCY34
5/6
5/6
8YZI1
BYZI2
8 -
6/6
NKT677
NKT7I1
6/-
5/6
,_
OC25 6/6
OC202
6 6
BCY3B
5/6
BYZI3
5/6
NKT734
5/6
Tnr
OC26 6/6
OA8I
1 6
BCY39
5/9
GET 1 02
41-
NKLT736
6/6
OC28 6/6
OAIB2
»-
BCY70
6/6
GET103
41-
NKT773
5/*
7- r>/p
2,400'
ia.»
OC35 6/6
OA200
2/-
BCY7J
10/6
NKT74I
6/6
NKT78I
6/-
7- UP
1,800'
12.'-
OC36 6/6
OA202
S-
BCY71
6/6
NKT242
6/-
2N696
5/-
7" STD
1,200'
V-
OC44 1/-
AC 107
61-
BFYI8
5/-
NKT244
5/6
2N697
5/-
5j- D/P
1,800'
1,200'
OC4S 2/6
AC 126
4/-
BFYI9
5/6
NKT245
5/6
2N706
4/6
8/9
OC46 1/-
ACI27
41-
BFY50
5/6
NKT26I
4/6
2N706A
4/6
OC70 1/-
ACYI7
41-
BFY5I
5/6
NKT262
4/6
5/-
5/-
sr STD
900'
6/1
OC7I 2/6
ACT IB
41-
BFY52
5/6
NKT264
4/6
2N2220
5'' D/P
1,200'
10/6
OC72 2/6
ACYI9
41-
BSY20
5/6
NKT27I
4/6
900'
91-
OC74 4/-
ACY20
5/6
BSY26
4/6
N KT603
6/6
5/-
5" STD
600'
5/-
1/9
OC7S 2/6
OC7B 2/-
ACY2I
ACY22
5/6
4/-
BSY27
BSY28
4/6
4'6
NKT6I3
6/6
2N2222
51-
OC7BD 1/-
AD 1 40
8'-
BSY29
4 m
VEROBOAF
: 3*- X 2*'
1/6;
3" UP
225'
2/9
OC8I 3/-
AD 149
«/-
BSY38
4/6
3J- X 2i~
4/3; cu
teer, ♦/-.
3' STD
ISO'
Hf-
OC8ID 1/-
AFII4
4/-
BSY39
4/6
DEE GEE
OCB2D 3/-
AFII6
41-
BSY9SA
4/6
16/- each.
SPEAKEI
25/6j 12'.
RESISTC
Spool*:
81 -. 5/6
7",
OCB2 31-
AFI 17
41-
BY 100
4,6
«; 3 t
19/6; 7"
KStiH
ihm, 5', 14/6; 8*
X4", 16/6; 3', 9/6.
.-.tt. 8d; •.■ watt, 6d,
2/3; 5!", 1'-; 3 , *M
3', 9d.
Send S.A.E. for eompl
ete list. P. & P.
1 -
A. MARSHALL & SON ( London ) LTD.
reels 2/9
otherwise
4/6.
28 Cricklewood B
roadway, N.VV.2
ELECTRO LYTI
:S: I5v 1 MFD up
Tel- 01-452 0161:2.
Dept. P.E
.19
to 100 MFD. 1/6 e
ach.
380
RECEIVERS AND COMPONENTS (continued)
MULLARD
AC 1 07
AC 127
AC 128
AC 176
AD MO
AD 1 49
ADI6I
AD 1 62
ACYI7
ACY20
ACY2I
ACY22
AFZII
AFZI2
AFI 02
AFI 14
AFII5
AFII6
AFII7
AFI IB
AFI86
AF239
ASY26
ASY2S
ASY29
AS 22 1
BAII5
BCJ07
BCI08
BC109
BCYIO
BCY12
BCY30
BCY3I
BCY32
BCY33
BCY34
BCY3B
BCY39
BCY40
BCY7I
BCZII
14/6
6/-
41-
6/-
12/8
11/-
7/6
7/6
3/-
3/6
4/-
2/6
10/-
11/9
18/-
4/9
4/9
419
4/9
91-
11/-
12/-
S/-
3/-
6/6
4/-
2/6
ffi
4/3
4/3
20/-
«/-
7/-
9/-
8/-
6/-
■/-
19/-
10/-
16/-
13/-
10/-
BFY50
*/-
BFY5I
s/-
BFYS2
6/-
BSX79
3/-
BTY79-4O0R
24/6
BTYB7-I50R
23/-
BTY91-I50R
33/-
BSX36-IOO
3/-
BTYB7-5Q0R
47/-
BYZIO
M/-
BYZI2
7/6
BYZI3
51-
BZY93 C24
12/-
BY1QO
5/-
BYX20-200
«/-
GET 1 02
5/4
GET 103
4/4
GETIII
10/-
GET573
10/-
OCI9
5/-
OC20
33/-
OC22
11/-
OC23
23/-
OC24
19/-
OC25
7/-
OC26
11/-
OC28
11/-
OC29
IS/-
OC35
»/6
OC36
13/-
OC4I
3/6
OC42
41-
OC43
»/-
OC44
»/-
OC4S
l'l-
OC7I
3/-
OC72
4/6
OC73
3/-
OC7S
3/-
OC76
3/-
OCBI
3/-
oca id
3/-
OCB2
OC82D
OC83
OC84
OCI23
QC 1 39
OCI40
OCI69
OCI70
OCI7I
OC200
OC20I
OC202
OC203
OC204
OC20S
OCP7I
ORPI2
ORP60
ORP63
ORP93
ORP90
OAS
OAI0
OA47
OA70K
OA73
OA79K
OABIK
OA6SK
OA90K
OA9IK
OA9SK
OA200
OA202
OA2I0
SX63I
SX636
SX63B
SZ20C
61 SV
SVC I
4/6
4/3
3/6
4/-
11-
12/-
11/-
*/-
4/-
6/-
6/-
10/-
13 -
8/-
11/-
I 0/6
19/6
97-
8/-
9/-
!•/-
19/6
3/-
41-
1/6
1/6
1/6
1/6
1/6
1/6
1/6
1/6
1/6
1/-
2/-
7/6
7/-
10/-
12/-
13/-
93/-
19/9
2N38 1 9FET 1 1 !-
2N3826 6/-
IB4QK10 19/-
I8I00-MOS 54/-
smcum
ADTI40 12/6
STI4I 5/-
ST140 §/-
NTEGRATED
CIRCUITS
Epoxy T05 8
lead nL 900 Buffer
vD 11/-
,uL 914 Dual Gate
a ii/-
uL923 J-K Flip
Flop Q 14/-
4-page reprint on
tC usage circuits
data, etc. 2/6
J.E.D.E.C.
2N385A
2N1BBA ..
13/-
2N696
9/-
2N706
4/-
2N706A , .
6/6
'2N7II
776
i 2N 1 1 32
10/-
2NI302
51-
2N 1 303
51-
2N 1 304
«/-
2N 1 305
61-
2NI306
8/-
2NI307
8/-
2NI308
10/6
2NI309
10 9
2N2I47 ..
17/-
2N2I60
14/9
2N2646 . .
10/-
2N3436 .,
6/9
PLANAR
BARGAIN
2N2926 Yell
OW
4 for 10/-
NEW G.E.
Over 1,000 tran-
slator and dtodc
types ex stock.
GUARANTEE: All the above-listed semi-conductor devices are Brand New, First Grade, and
guaranteed. We will replace at no charge an/ device found to be faulty. Further: all devices
carry the Manufacturer's name or Trade Hark, type number and batch number. We do not
offer for sale devices often described as "new and tested" or bearing re-marked type numbers,
these often have a short and unreliable life. LST COMPONENTS
Resistors: i Watt 5% Miniature type,
low noise— high stability. 10, 12, 15,
18. 22, 27. 33, 39, 47, 56, 68, 82 and
decades to 820K. 1-25 pieces, 4d ;
25-99, 3d ; 1 00 pieces or over, 2d each,
10% tolerance, i Watt, I Meg, to B-2
Meg., same price.
Preset potentiometers. Standard or
Subminiature types, 20% tolerance,
Lin. vertical or horizontal.
100. 250, 500 ohm, Ik, 2 -5k, 5k, 1 0k,
25k. 50k, 100k. 250k. 500k, I Meg, 2 5
Meg, 5 Meg. All at 1/6 each. Discounts
for quantities over 12 of I value.
COMPONENTS
7 COPTFOLD ROAD
BRENTWOOD ESSEX
BRENTWOOD 7904
24 HOUR POSTAL SERVICE
"X" LINE MODULES
Send for details of
our range of ready-
built solid-state
circuits, amplifiers,
sirens, light flashers,
etc.
FAIRCHILD AF 11
20W SOLID STATE
AMPLIFIER KIT
£8.8.0 Complete
Includes Printed circuits
board, Semiconductor!,
Resistors, Capacitors,
Heat sink and short
circuit protection com-
ponents. S.A.E. for
details.
1968 CATALOGUE
34 pages —
NOW AVAILABLE
send 1/6 stamps
POST * PACKING 9d
per order
EXPORT ENQUIRIES
WELCOME
TRANSISTOR MANUALS
O.K. New Edition 29,<<J
R.L'.A. Latest Edition 87/8
+ 2/8 Post & Packing
RETAIL AND WHOLESALE
SUPPLIED
REDUCED PRICES
2NI073BPNP I20v 60W I.SMHi (TO-41 can)
10,'-. 2NI290 Electrically as 2NI07JB {TO-3 can)
10,'-. Ex-equipment, tested, either type 5/- each,
5 for 20/-. Rechargeable bate, DEAC 12.2v 450
mA/hr 17/S, P. & P. 2/6. P/cct board Edge Con-
nectors, 0.2 matrix, 12 way 2/6, 1 7 way 3/-, 22
way l/o, 30 way 4/6, 32 way 5/-. 2W pots, 1"
spindle, 5k, 2k, Ik, 500, tOO ohms. I/-. Pre-set,
min, pots jW 270k, 1 00k, 330, 270 ohms. 9d.
Terms C.W.O., Min. order 3/-. P. & P. I/-.
S.A.E, for list. Mail order only.
T. L.WILLIAMS
2 CHESTNUT CLOSE, ADDLESTONE. SURREY
STUDENT ELECTRONIC SERVICES
194 Regent Road, Sal ford 5
We stock a wide range of Resistors i and
i watt.
Buy individually OR try the S.E.S. Pre-Pack.
Stocks now include Potentiometers — Log,
and Lin.
Enclose 6d . for complete price list
FANTASTIC OFFER ! ! !
Computer printed circuit boards.
Comprising transistors, diodes, reiiiton,
etc* Ideal for constructing amplifiers,
receivers, etc, etc.
Price: 3 boards for only 10/- P. ft P. 2/-.
TELE-RADIO (1943) LTD.
IS9 Edgware Road, London, W.2
SUPER QUALITY NEW RESISTORS
Carbon fi/m, tow noise, high stops:
Power Range Series Per doz. Per 100
*W S%SIO to330ktl E24 1/10' M/6
iW 10% In to 4-7 [] EI2 +^d per resistor
1/9
2/2
3/3
13/6
17/-
25/10
Jtt iuy i 14, m t r u
W 10% 4 7() to I0MQ EI2
±W 5% 4-7[) to I0MO E24
IW 10% I0Q to I0MQ EI2
1/6 per 100 less in IOC's of one ohmic value.
Please state your choice of values.
Quality Carbon Skeleton Pre-iet*: 1000,250(1,50012, I ko, 2kll, 2-5kfi, 5kO,
IOktl,20kO,2SkQ,50kO, lOOkfl, 250kQ, SOOkfl, I M0.2MO, 2-5MO, 5MO, I0MO.
Available in horizontal or vertical mounting, I/- each.
Low Cost Volume Controls! I00O, to I0MO, I in., 2/3 each: Ska toSMQ.log..
2/3 each.
Log. Stereo: lOOkQ, 250kfl , SOOkO, I M Q. 2Mo, US., 9/-. O.P.sw. 12/6.
Ceramics: 100, 220, 470. 1.000. 2,200, 4,700 P F, SOOV, 5d: 0005. 001. 0-02.
0-OSuF, 50V, 5d.
Electrotytics: S, 10, 25, SOuF, 10V, S, (O^F, 25V, »d; 100, 200^F, (0V, 25,50^F,
2SV. I/-.
Sub- min. C426 range: all values in stock.
PICK OF THE NEW SEMICONDUCTORS
Silicon, many types including;
BCI 07, 45V, I] (25-500. 4/-. BCI67, S0V, 1 25-500. 3/-,
BC108, 20V, 125-900, 3/1 1. BC 168, 20V. ! 2S-9O0, 2/6,
BC 1 09, 20V, 8 240-900. 41-. BC 1 69. 20V, 240-900. 2.'».
BCI09 and BCI69 are low noise types, BCI67, BCI6S and 8CI69 are plastic
Best Value For:
Power: 2N3055, I ISW, I00V/I6/6; 2N3054, £1,
Field Effect: MPFI05, gm 2 to GmAIV, 10/-; 2N3BI9, 14/6,
VHF and Fast Switching: BSX20 ft. 600MHz, 4/6.
High Gain: 2N3390. B400-I.250. 6/-.
Low Noise: 2N3707, 5/-; 2M339IA, 5/6; 2N40S8 (PNP), 5/6.
Sub-Miniature: SCI 22. 30V. 50mA, BOmW. 250MHz. 6/6.
Low Cost: 2N2926, 18V. 120MHz, 1/6 (our colour selection)
Also: 2N3702, 2N3703, 2N3704, 2N3705, 4/- each; BCI09C, 4/3; BFY50 3/3,
Germanium, many types including:
RP, VHF: NKT603F, 6/-; NKT6I3F, 5/9; NKT677F, 4/5.
Low Noise: 2G308, 6/9; 2G309, 7/9; NKT275, 3/8.
PEAK SOUND PRODUCTS
CIR-KIT No, 3 Pack, 12/6. Adhesive copper 5ft >, ±in or .'.in. 2/-; 100ft • Jin
or Am, 30/-. Perforated board 0-ltn matrix Sin x 3Jin, 4/-; 2£in •; 3|in, 2/6;
2in x 3t'm, 2/-. Also SA-8. Stereo Amps at attractive prices .
TRANSISTORISED STEREO AMPLIFIER AND PRE-AMP 5AB-8
Complete kit of this very popular amplifier.
16 watts
total output, £10.10.0
Power supply kit, £3
Cabinet, £1 ,
IS", B DISCOUNT an whole order and post free when pur chasing en SA6-67
The most successful amplifier of its kind yet, A real money saver.
Old-Timers: 2NI302, 2NI303, 3/6; 2NI304, 2NI305. 4,-: 2N1306, 2NI307, 6>;
2NI30B, 2NI309, 7/11.
High Power: NKT403, 14/10; 2N2I47, 16/9; matching, I/- pr.
Complementary Output: AD 16 1 INPN), 9,'-; AD 162 (PNP), 9/-.
Silicon Diodes:
Low cost: IS940. 30V. 75mA. 1/3; OA202. 150V, 160mA, J/-: BY238. 850V,
500mA. 3/11; IN5054, BO0V, IA, 4.9.
Zener Diodes: 400mW. S%, 2 7V to 33V (E24 values), 3/3.
Germanium Diodes: OA47. 1/9; OA70. 1,9: OA8I, 1/6; OA90. l/3;OA91, l/ll
OA95. 1 13.
ALL GOODS BRAND NEW • NO SURPLUS • FAST DELIVERY
Discounts: 10% over £3; 15% over £10.
Post and Packing; I,'-; free on orders over £1.
Catalogue: Send I - stamps — includes data on all types in stock and many
equivalents.
ELECTROVALUE 6 MANSFIELD PLACE. ASCOT, BERKSHIRE
381
RECEIVERS AND COMPONENTS (continual)
ADROI ELECTRONICS
Lord Alexander House
Water house Street
Hamel Hempstead, Herts
OC28
OC3S
OC36
OC44
OC45
OC70
OC7I
OC72
oca i
OCI40
OCJ70
OCI7I
2N696
2N697
2N706
5/- 2N2646
7/4 2N2926
8/6 2N3Q53
1/9 2N3055
1/9 2NI482
2/ J 2NI720
2/- N KTI 24
2/- N KTI 25
1/3 N KTI 26
4/4 NKTI27
2/3 N KTI 28
12/4 NKTI29
4/4 NKTI4I
Sj- N KTI 42
4/3 NKTI43
12/4
5/-
10/-
19/-
5/-
4/4
a/4
s/-
s/-
8/6
S/9
S {~
S/9
5/-
4/9
NKT2! I
NKT2I2
NKT2I3
NKT2I4
NKT2IS
NKT2I6
NKT2I7
NKT2IB
NKT2I9
NKT22I
NKT022
NKT223
NKT224
NKT225
NKT226
4/9
4/4
4/4
J/4
3/4
1/1
'/»
4/1
4/7
4 8
4/-
4/1
3/6
3/6
8/9
NKT227
NKT22S
MKT60I
NKT6I2
NKT6I3
NKT674
NKT675
NKT676
NKT677
TK20C
TK40C
OAS
OA8I
OA200
OA2I0
8/3
4/1
S/9
4/8
4/9
5/-
4/-
4/1
4/1
1/4
V-
1/-
&
«/*
BRAND
NEW
G
U
A
R
A
N
T
E
E
D
Send 94. stamps for complete list* Transistors. Rectifiers,
Integrated Circuits, Etc.
Cosh with order please. Postage 9d.
Airmail extra
R 6c R RADIO
51 Burnley Road, Rawtenstall
Rossendale., Lanes
Tel.s Rossendale 3152
VALVES BOXED, TESTED * GUARANTEED
EBF80
3/-
PCC84
3/-
PY82
^^
EBFS9
3/6
FCF80
3/-
UI9I
4/»
ECC82
3/-
PCF82
3/6
U301
4/6
ECL80
31-
PCL82
4/-
6F23
5/-
EF80
1/6
PCL83
4/-
I0PI4
3/-
EF85
1/-
PCL84
5/-
2QP5
3h
EFI83
3/4
PL36
3/-
30FS
3/4
EFI84
3/6
PL8I
41-
30LIS
*/-
EYB6
4/-
PL83
41-
3DPI2
4/6
EL4I
s/-
PY33
tl-
30CIS
Sh
EZ40
4/6
PYBI
1/6
30PLI3
S/6
EBC41
4/6
PY800
3/6
30PLI 4
5/6
POST, ONE VALVE 9d. TWO TO SIX 6d.
OVER SIX POSTPAID,
BI-PAK SEMICONDUCTORS
(DEPT. E)
8 Radnor House
93/97 Regent St
London W 1
UNIJUNCTION
■ ITJC Eqvt. 2X3846, T /Z
U 140 TIS43, BEN 3000* / °
SIL. REaS TESTED
PIV T40mA 3 A 10 A 30 A
M
toe
•00
800
600
con
ISO
800
;r)'jn
a/o
4/-
4/8
4,9
■/- 4/0 9/0
■/) 3/0 •/- 15/-
2/0 4/0 6,8 20,-
8/- 4/8 •/- 22/-
o/- 9i- ta-
rn 9/6 30,'-
71- 10/- 37,'-
Bj- 18'- 40/-
8'- 10'- 17/6 50,-
SCR's WJWB8T PRICE
* V LARGEST RANQE
PIV 1AMP 7A ISA 30 A
26 — 7/0 — 80/-
50 7/0 8/6 10/8 35/-
100 8/8 10/- 167- 45/-
200 18/8 15/- 80,'- 65/-
300 15/- 20/- 25/- —
400 17/0 29/- 34/- 80-
600 30/- 40/- 46/- 85/-
600 — 40,'- 60/- —
SCR MANUAL 25/-
3rd Edition. P.P. 2,'fi
OfiP 12 Q/£
ORP 60 °/ w
OCP 71 EACH
SYLVAN I A (USA)
IN2I BMR
MATCHED PAIR
MICROWAVE
DIODES
1 IK21B and I IN21BR S
BARD MIXER DIODES
15;- per pair. Brand Sow
in Manufacturers Original
Packages.
* QUALITY-TESTED VALUE PAKS * BARGAINS *
2 DHlt Trims. 2N1226 Germ, FNF lOOMu/e 10/-
B Matched Trans. OC44/45/8I/81D 10/-
[6 Red Spot AF Trnos. PNP . - 10/-
[8 AVhlte Spot RF Trana. FNP 10/-
5 8 II (ton Reels. 3 A 100-400 P1Y 10/-
2 10A Silicon Rcets. 100 F1Y 10/-
2 OC1 140 Irani. NPN Switching 10/-
1 12A SCR 100 PIV 10/-
3 All. Trans. 2S303 TNP 10/-
4 Zener Diodes 250in\V ;(-12V 10/-
■A 200Mc,'a Sil. Tram. NTN BSY26/27 . - ■ 10/-
3 Zener Diodes 400mW 33V 5% Tol. ... 10/-
4 High Current Tran:". OC42 Eqrt , 10/-
2 Power Transiitora 1 OC28 1 OC3S . . 10/-
5 Klllcnn Beets, 400 V1V 260mA 10/-
4 OC75 Transiatom Milliard Type 10/-
1 Power Trans. OC20 )00\ r 10/-
4 OA202 Sll, Diodea Kub-miii 10/-
2 Low Koine Trana. NFS 2N92M/30 10/-
1 Bit. Trana NPN VCB 100 ZT86 10/-
H OAS 1 Diodes Sub-niiii 10/-
4 OC72 Transistors 10/-
4 OC77 Transistora 10/-
3 Metal Alloy Trana lit on Mm. Type 10/-
4 Sil. Recta. 400 PIV OOOmA 10/-
4 OET884 Trans. Eqvt. OC44 10/-
5 rt£T883 Trans. Eqvt. OC43 10/-
2 2N708 Sil. Trana. 300Mc/s N PN 10/-
5 CT41/45 ficrm. Trnns. PSP Eqvt, OC71 10/-
:* OT31 LF Low Noise fierni. Tram. PSP 10/-
8 IN9I4 Sit. Dkides 75 PIV 75mA 10/-
OA95 Germ. Diodes Sub-niin 10/-
3 NPN (Jerm. Trans. NKT773 Eqvt. AC180 10/-
10/-
10/-
10/-
10/-
10/-
10/-
10/-
10/-
10/-
10/-
10/-
OC22 Power Trana. tier"
OC25 Power Tram, (ieriu
OC73 Milliard Trans
AC 128 Trans. PNP High tiain ...
AC127/128 Comp. pair PST/SPS
2S 1307 PSP SwitchinK Trana. ...
CG62K Germ. Diodes Eqvt. OA71
AF118 Milliard Type Trans
Assorted Germ. D^dea Markeil .
AC126 Genu. l'NP Trana
1 A Germ. Beet. 200 PIV
1 ORF61 Phut u -conduct ivo cell 10/-
4 Silicon Reets. 100 PIV 700mA 10/-
3 AF117 Trans. Mullard Tv-pe 10/-
7 OC81 Type Tran* 10/-
3 OC171 Trans. Mullard Tjik: 10/-
8 2K2928 Sil. Eposy Trana 10/-
7 OC71 Tvpe Trans 10/-
!5 Trana. HeatsinkB fit T018, S012, ctt. . . 10/-
2 2S701 Sil. Trana. Texas NPN 10/-
3 12V Zenere 400mW 10/-
3 IW 5.6 Zenera 10/-
4 OA10 Diodes Mullsrd 10/-
5 20417 Eqvt. AF117 10/-
8 OA70 Diodes Mullard 10/-
4 OA47 Gold Bonded Diodes 10/-
2 I0A 600 PIV 811. Recta. 1S425R ...... 15/-
2 Zener Diodes 20W 18 and 22V 16/-
1 2N910 NPN Sil, Trans. VCB100 «0Mc/» 16/-
2 1,000 PIV Sll. Rects. l.SA R8310 AF . 15/-
3 BSY05A Sil. Trans. NPN 200Mc/s .... 15/-
3 OC200 Sil. Trans. 15/-
2 SH. Power Rects. BYZ13 16/-
1 Sil. Power Trans. NPNIOOMc/s TK201A 15/-
8 Zener Diodes 3- 16V Sub-tobi 15/-
1 2N1132 PNP Epltailal Planar Sll, Trnns. 15/-
3 2N607 Epitaxial I'ltuinr Trana. 811 16/-
4 Germ. Power Trans. Eqvt. OC18 Mullard 16/-
1 I'll I Junction Trans , 2N 2646 Eq v t . D5E2 9 16/-
2 Sil. Trans. 200Mc/a 80\'eb ZT83/H4 . . . 16/-
I Sil. Planar Trans. NPN 100 Mc/s BSY25 15/-
1 Tonnel Diode IN 3720 ( TD5) G.E 15/-
1 I"nJiunctionTranB.2N2160TO-5canfi.E. 16/-
2 Sil. Beets. 5A 400 PIV Stud Type 15/-
2 Oerm. Power Trana. OC28 15/-
1 Tunnel Diode AEY11 10o0Mc/h 8TC. . 15/-
3 2N2732 Sll. Epoiy Planar HFE22S nla\. 16/-
6 BY 100 Type Sil. Recti 80/-
25 Sil. and Germ. Trans. Mixed, all marked
New 30/-
10 Xew Power Trans. OEC Eqvt, OC16/26 30/-
FREE
One 10/- Pali ol your own choice
free with orders valued £4 or over
BI-PAK 7
"SPECIAL"
SILICON PLANAR
TRANSISTORS
• SIMILAR 2N706
J^ONLY I/-
each
■«>
NPN FULLY
TESTED
* QUALITY-TESTED DEVICES *
ACI25 2/3
AC176 , 5/6
AF139 10/-
AFZ12 10/-
BC107 5/-
BC108 6/-
BC10B 6/-
BCY3.1 5/-
BCY34 6/-
BCZI0 5/-
BCZ11 «/-
BFYOO 71-
BFY51 7/6
BFYoS 7/6
MAT10O 8/-
M.1T120 8/6
NKT773 41-
NKT781 6/6
OC44 .■■■ 1/8
OC45 1/8
ST140 8/-
ST141 4/-
2N6S0 */B
3N697 5/-
2N1000 4/8
2N1300 4/-
2N2147 15/-
2K2804 8/-
2N3819 16/-
2N3820 - 25/-
2S303 5/-
3S303 */-
•■JS30-1 6/-
ftLUT
10/-
PER PAK
120 Glass sub-mi[i Germ. DIODES
K1N6 OF THE PAKS "SUPER-PAKS"
UNEQUALLED VALUE AND QUALITY
BRAND NEW UNTESTED SEMICONDUCTORS
SATISFACTION GUARANTEED IK EVERY PAK
60 Mixed Germ. TRANS.
75 Gold Bonded Germ. DIODES
40 Lite DC81, AC128 Berm. THAHS.
60 Silicon 200mA sub-min. DIODES
40 Sil. Planar NPN TRANS.
16 Top-Hat Sil. Rect. 750mA
50 Sil. Planar DIODES 250mA
20 ZENERS 1 wan mixed volts
150 Mixed Sil. Germ. DIODES
20 BAY50 charge storage DIODES
12 Epoxy Sil. Rects.
30 PNPSil.PtanarTrans. like2H113Z
6amp Sil. Rect. Sim. BYZ13 Type
30 TO-5 NPH Sil, Trans. BFY50,
2N696 Type
30 Germ PNP AF Trans. TO-5 like
ACY17-22
30 NPN PNP Sil. TRANS.
10 3A Sil. RECTS. (Stud Type)
30 Like BGI08 Sil. NPN TRANS.
12 l.SA Sil. RECTS. Top
30 AF Germ Alloy TRANS.
10 1A Glass Sil. RECTS. high volts
30 MAOT's MAT series PNP TRANS.
20 Germ. 1A REGTS. GJM series
25 3D0M/CS NPN Sil. TRANS.
30 Fast Switching DIODES IN914
Overseas
Our vast stocks change daily with hundreds of Semi- Minimum Order 10/-. CASH WITH ORDER
conductor bargains becoming available. Juit send 2/6 ! PLEASE. Add I/- postage and packing per Order,
to cover 3 months mailing of our latest stock lists, j GUARANTEED by return postal service,
eqvt. charts, circuits, etc. I add extra for Airmail.
BI-PAK GUARANTEE SATISFACTION OR MONEY BACK
382
RECEIVERS AND COMPONENTS
(continued)
Trintiitor larrlte rod aerials, M\v and KW Sm long.
5/- no data.
Smalt 7 traDiittor radios ideal for BpHres. or repair,
in maker* liases with 4 nickel cadmium batteries,
battery charger, leather case, start (Oiled nnd no
nutir.iHirr, bargain •> 22 8 + -2 • P. ,v I' .
Double gang potentiometer!, 250k + 200k log..
500k + 6fi0k I In, 3 - each.
Ferrlte rodi, ,', 31 in, 01 each.
Disc oeramior, l.nOOpf [P.C, type) ehort leads, 3d
each: Hi do* (6TO VWi.
Transistor capacitor*. OlmF 50 VW, 4d each; 8/- doz.
»iiF 8VW. M: 4mF 64VW, SOrriF 8VW, lOOmF
BVW, lOniF 12VW. 6d each; lOOmF BVW. ISOmF
12VW. SSDinF BVW. Sd each; -iOOmF 16VW .
SOOrnF 9VW 1 '-.
Set ol 3 transistor double tuned LP. transformers
UTOk.-m, 10'- with circuit.
Mixed baa ot silver mica capacitors, 100 (or 8 -.
Mixed bar o( silver mica and tabular ceramics,
100 (or 9<- (our selection).
Traniiitors, fiT-lftB (OC45) 1,8 each.
Zener diodes. OAZ247 B,.'8. OAZ224 3,8. IB7051A,
I87076A 8/8.
P.C. board, ilnule sided. ft in. thick, appro*. Sin. :<2in.
4d; 41n.x4>ln., 9(1.
Folfittrene capacitors, 1.000 pF 6%, S.OOOpF 11%,
3d each; g/8 doi. (30VW).
Silver mica capaclton, 25, 30, 47, 40. 75, ?2. 137,
220, 330, 375. 500, l.OOOpF, wire ended, .150 VW;
80. 230. 300. 370. 505, 680, 1,100, 1,600 pF. P.C.
type, 200V W.
Minimum order 5.'-.
POSTAL SERVICE ONLY. Poatane; under £1.
1/8; £\ to «2, 2/3. Over £3 post (rec. S.A.E. (or
lists.
A. J. H. ELECTRONICS (G8A0N)
5BWAVERLEY ROAD, THE KENT
RUGBY, WARWICKSHIRE
STUDENT ELECTRONIC SERVICES
194 Regent Road, Salford 5
Constructional aids — including
Assembly Stand (each individually
made by craftsmen).
LEKTROKIT— the biggest money and
time saver since the
safety pin !
Everything to construct a pro-
fessional job, from a variety of
boards, pins to chassis plates and
rubber feet.
Special introductory kit in 2 sizes.
Write now for complete price list
AND sample resistors, enclosing 6d,
TRANSISTOR CAPACITORS (ELEC-
TROLYTIC)
5 00 mfd 4V 64 mfd 40V l6mM 25V
320mfd 10V SO mfd 10V lum'fd 25V
250mfd 4V 30mfd 10V e-4mfd 64V
200mfd 16V 25mfd 25 V 4mfd 64V
lOOmfd 16V 20 mfd 12V I mfd 25 V
I/- each. 9/- per doz. Min. order 10/-
TRANSISTOR PANELS— OC45 or equiv.,
20 Tor 20/-. JO— IS/-, 50—35/-, 70—45/-, 40—
10/-, 60 — 40c, 80— 50,'- Postage 2/- per panel
Brand new STC sit. EPT planar transistors
300 Mc/s 350 mW, all at 2/- each. 2N743,
2N753. 2N9I6, BSY26. BSY28, BSY6S, BSY18,
BSY95A. BSY29
TRANSISTORS OC4S. TK22C ® I/- each.
OC76. OCI 39, 2G302, OC8I , OC44 8, 2/- each.
GET 1 20, OC83, IN 1 308, OC72, NKT2I6 @
41- each. OC23, NKT452, NKT453 W 6/- each
10 watt heat sink drilled for power trans, 5/-,
I.OOOmfd 30V 4/-. 3.000mfd 10V 2/-, T.V.
capacitors 100 + 200 + 400mfd 27SV 7/6,
100 + 2O0mfd 300V 5/6.
W.W. POTS 5, 10, 25, 50, 100. 250. 500 ohms,
Ik, 2k, 2-5k. 5k, 1 0k. 25k, 50k, 1 00k, not
preset!/- each. Min. order 5/-. Postage 1/-
ZENER DIODES— 2-4, 2 7, 3 6, 4 75, 5 25.
5-75. 6-2, 68, 7-5, 91, 13, 15, 16. IB. 20, 27. 30,
33 volts, 3/6 each, mostly I watt
POLYSTYRENE CAPACITORS 350V: 180.
270, 330, 390, 470, 560, 680, 820pf. 1 ,800, 2,200,
2,700, 3,300, 5.600. 6.800. 8.200
I2SV: 1,200, 1,500. 1,800, 2,200, 2,700. 3,300.
3,900, 4,700, 5,600, 6,800, 8,200. 012, 015.
BOpf ceramic 200pf S.M. any selection 2/< doz.
4-40pf trimmers 41- doz.
BRAND NEW BOXED CHASSIS, contain-
ing 2— OC35, 2— OC29 12 WW resistors JO/-.
Postage 1/6.
STEREO POTS, Less switch, single spindle.
I meg -r I meg log and I meg log -r 1 meg rev/
log, 7/6 each.
NEW CROSS RADIO
6 OLDHAM ROAD, MANCHESTER 4
RECEIVERS AND COMPONENTS
(continued)
RESISTORS
5 watt carbon Film 5%
All preferred values in stock from
10 ohms to 10 megohms 2d. each.
Send S.A.E. for free sample
CAPACITORS
Mullard Miniature Metallised Poly-
ester P.C. Mounting, all 250V D.C.
working. 0-01 mf, 0022mf, 0047mf,
0-lmf. 0-22mf, all at 6d. each
Hunts tubular (mf 200V working
at 3d, each
Send 6d. stamp for extensive list of
low priced Electronic Components,
Instruments and Equipment
Please include I /- postage and packing
on all orders under £1
Dept. P.E.11 -
BRENSAL ELECTRONICS LIMITED
CHARLES STREET, BRISTOL 1
PHOTO ELECTRIC CONTROL
QVQTT1I Comprises a light source unit with
OIuILitI optional Infra Hed Biter and lens
system to force the light. Also a
photo-electric Relay control unit. Both housed in
metal ca&es for bench or wall inn mat hit*, sensitivity
control, mains on-oft switch. Works from 23Q/240V
a.c. Mains, Can be used as a simple on-off switch by
breaking the beam of light (invisible if Infra Red
Alter is asedl and as such It will operate as a burglar
alarm, or will open doors, etc. Also in conjunction
with a counter or other equipment it will per Jam i
many functions ht the factory or /Q I Q A
warehouse. * 1VT. I 7.%I
P.M. WIRELESS MICROPHOHE
84.104Mc/s. Transistorised. Operates from 9V
battery. Complete with arlditiontil secret tie clip
microphone. List £12/ 10.'- ON XV £jL I C A
These cannot be operated In l*.K. a^w, I J.v
TBAHSISTORISED FK TTJHEB
« TKAS8I9TOR MKiH QKALITY USER.
SI2EOSLY6inx 4in X 21 In 3 l.F. stages. Double
tuned discriminator. Ample output to feed most
Amplifiers. Operates on BV batterv, Coven^e
8S-108Mi::b. Ready built ready for tjL I "F f.
use. Fa ntastic value for money "' *
FM MULTIPLEX STEREO ADAPTOR
Printed circuit biscuit, 4 trans. 6 fC IQ i
diodes 9V with lull instructions fcrf " ' '* v
BSR TAPE HEADS
R£« 39/6 pair
BSH TAPE HEADS
■ALL \Q If.
4 TRACK JT /° f 3 "
REFLEX CONE TYPE
WATERPROOF SPKR.
watt. 8 ohm. 300-
lfl.OOOc's PA £A C A
* Music Uelav fc^'J'W
MULTIMETERS \J I
from J ' t /
LOUDSPEAKERS. J'Q
40ohni.21"80ohin. 3/0
IT TWIN CONE 10 M/
watt, la or 3ohm Oil/"
!'29/6
TWEETER 1*i ohm
10 watt, I8K-CPS
CROSSOVER NET- in/
WORK 1« ohm If/"
SUPER SILICOH RECT. T.V., etc, 1.200 P1V
800mA. 8'-; or complete with Instr. resistor,
condenser, 7/B; 400 PIV HW 8A, «;-; 200 PIV HW
6A, t!-.
Stamped envelope fur lull selection an I hargaiu
oilers In Multimeters, Radios, Baby Alarms, Inter-
coms, Walkie-Talkies, Rectifiers ami Eagle Lists.
UNDER £1— P. & ¥. 8d. OVER £1 post free.
C.O.D. 3/6.
DURHAM SUPPLIES
17SF, Durham Road, Bradford, 8, Yorkshire
PLEASE MENTION
PRACTICAL ELECTRONICS
When Replying to
Advertisements
The RADIO AMATEURS
HANDBOOK 45/-
1968 Ed. by A.R.R.L. Postage 4/6
COLO U R TV PAL SYSTEM, by Pateheu.
4M/-. P. & P. 1/-.
F.E.T. CIRCUITS, by Turner. 25/-. P. & P.
I/-
BRIDGES AND OTHER NULL
DEVICES, by Turner. It/-. P. & P. I/-.
ABC'i OF TRANSISTORS, by Mann.
20/-. P. & P. I/-.
RAPID SERVICING OF TRANSISTOR
EQUIPMENT, by King. 30/-. P. & P. I/-.
HI-FI YEAR BOOK, I96S EDITION,
IS/-. P. & P. I/-.
101 WAYS TO USE YOUR OSCILLO-
SCOPE, by Middleton. 21/-. P. & P. I/-.
COMPUTER CIRCUIT PROJECTS
YOU CAN BUILD, by Boichen. 24/-.
P. & P. I/-.
TRANSISTOR SUBSTITUTION
HANDBOOK, new 7th edition. 15/-.
P. S P. I/-.
SILICON CONTROLLED RECTI.
FIERS, by Lycel.- 21/-. P. & P. I/-.
Where possible 24-hour service guaranteed
UNIVERSAL BOOK GO.
12 LITTLE NEWPORT ST., LONDON, W.C.2
(Leicester Square Tube Station)
"PLUS-3" MAINS CONVERTER
Provides three separate
switched output voltages
6v„ 7iv. and 9v. D.C
Suitable for all types
of transistor equipment,
radios, amplifiers, record
players, etc Attractive
case with indicator light,
ma ins lead, output socket,
plug and lead. Size
41' X 3i' X 21*.
P. & P, m
(Extra lead with din plus (or cassette recorders 7/t)
Mains unit for Ft-Cord 202A f4.15.lt. p. & p. 5/,.
R.C.8. PRODUCTS (RADIO) LTD.
(Dtpt P.E.), 31 Ollnr Road, London, E.17
REPEAT OFFER OF CIRCUITS
• NOUGHTS AND CROSSES MACHINE
• BINARY ADDFR MD SDBTRACTOR
• FOOTBALL POOL COMPUTER
• KULTIPLYIN6/0MDING AHALQBUE COMPUTER
• SIMULTANEOUS AND QUADRATIC EQUATION SOLVERS
All these circuits for 4/6 post 6d. Diagrams
(9 pp.) text (26 pp.) parts and price lists. All
purely electrical designs. We are the leaders
in rhis field and can put a dare en the publi-
cation of each circuit to show that we were
the first. Our machines have appeared at
exhibitions in this country and abroad, before
learned societies and the TV cameras and
have even made money Tor charity.
Again showing that we lead, we have under
development a new circuit, which will Add
and Subtract Binary numbers both in parallel
and serially as in a full scale computer. The
formation of the Sum and Carry is shown step
by step. This will prove an invaluable aid to
teaching binary arithmetic and computer
method. Full details available shortly.
PLANET INSTRUMW CO., 25(E) DOMINION AY., LEEDS 7
383
ERSiN
for quick,
Contains 5 cores of non-corrosive flux, instantly
cleaning heavily oxidised surfaces. No extra flux
required. Ersin Multicore Savbit Alloy also reduces wear
of copper soldering iron bits.
&&*
SIZES
HANDY SOLDER
DISPENSER
Contains 10 ft. coil
of 1 8 s.w.g. Ersin
Multicore Savbit
Alloy. 2/6 each.
SIZE 15
SOLDER
DISPENSER
Contains 21 ft. coil
of 60/40 Alloy,
22 s.w.g. Ideal for
small components,
transistors, diodes,
etc. 3/- each.
SIZE 12
jf Ideal for home
~ constructors.
Contains 90 ft.
of 18 s.w.g, Ersin
Multicore Savbit
Alloy on a plastic
reel. 1 5/- each.
BIB MODEL 8
WIRE STRIPPER
AND CUTTER
Strips insulation
cleanly and
quickly, fitted
with unique 8
gauge wire
selector. Plastic
handles. 9/6 each.
*
From Electrical and Hardware shops. If unobtainable, write to:
Multicore Solders Ltd., Heinel Hempstead, Herts.
SHORT WAVE ONE VALVE
RECEIVER KIT
39/6 + 2/6 P.P.
PEAC ANALOGUE COMPUTER KIT III STOCK
UNIT 'A' COMPLETE £26.0.0 + 1 5/- P.P.
Punched aluminium panels and
case for above £4.17.6 + 5/- P.P.
CLUBMAN Mk. I KIT COMPLETE £6.17.6 + 5/- P.P.
Without metal work £4.12.6 - - 2/6 P.P.
CLUBMAN Mk. II KIT COMPLETE £10.17.6 + 5/- P.P.
Without metal work £8.12.6 -;- 4/6 P.P.
EXPLORER KIT COMPLETE £4. 2.6 + 2/6 P.P.
STABILIZED POWER SUPPLY KIT 0-20V. 500ma
COMPLETE £4.17.6 + 5/- P.P.
COMBINED AUDIO OSCILLATOR AND FREQUENCY
METER £17 + 10/- P.P.
PORTABLE TEST UNIT KIT
FLUORESCENT CAMPING LIGHT IN STOCK
S.A.E. FOR TRANSISTORS, SEMICONDUCTORS, FULL LIST
700 TYPES
3 SILICON RECTIFIERS, BY 100 TYPE 10,-
10 MIXED MARKED TESTED TRANSISTORS 10/-
40 UNMARKED UNTESTED TRANSISTORS NEW 10, -
1 LIGHT SENSITIVE CELL ORPI2 8/B '
25 MIXED UNMARKED TESTED TRANSISTORS 10/-
2 TRANSISTOR COMP. PAIR AD 16 1/162 16 -
P.P. I/-
OUR COMPONENTS CATALOGUE 5 - Post Paid with 10;- worth of
discount vouchors.
OLRUS ELECTRONICS LTD.
748 HIGH ROAD, LEYTONSTONE
(NEXT TO GREEN MAN}
LONDON, E.11. Tel. 01-989 2751
CALLERS WELCOME— CLOSED ALL DAY FRIDAY
HTOH SPEED HAGIfETIC COTJHTERS (4X1X1 in). 4 digit. I2/24/4SV. (elate
which) B/8 each, P. 6 P. 1/-.
COPPER LAMINATE BOARD (8 1 X fllX i.in). 2/fl eueb. 5 ior 10/-.
BB-8ETTABLE HIGH SPEED COUNTER (3 x 1 X Sin). 3 digit. 12/24/48 V. (state
which) 8B/B each.
BULK COMPONENT OFFERS
104 Capacitors SOpF to .ifiF.
260 Carton Resistors i & jW. (Transistor types),
360 Carbon Besistors i * IV.
100 Ceramic Capacitors 2— lOOOpF.
25 Vitreous V[W Resistors (0%).
12 Precision Resistors ('1% several standard values Jiidiadctlj.
26 Close Tolerance Caps. (2%).
12 Silicon Diodes 600 p.i.v. 750 HI. a,
4 Silicon Rects. 400 p.t.v. 3 amp.
8 Silicon Beets. 100 p.i.v. 3 amp.
60 Silicon Trans. (2N706/708. B8Y2B/20. BCY41/42 types.) I'uuuirkcd, Untested,
60 Silicon Diodes 200 m.a. 100 p.i.v. Sub. Mm.
ANY ITEM 10/-, ANY 6 ITEMS IS.
8.C.R.. (Thyristors, CRS1/20 S/8; CRS1/40 7/8; CRS3/10 7/S; CRS3/30 8/0;
CBS 3/40 10/-: CRS3/50 12; 6 each.
'WOO' TYPE RELAYS (es. new equip.) 10 for 25/- (our choiie) p.p. 5/-,
PATTRIGK & KINNIE, 81 Park Lane. Romford, Essex
ROHford 44473
PEAK-
SOUND
8 + 8W.
TRANSISTOR STEREO AMPLIFIER in kit form
BoJJd Oil lor £9.10.0 (4/8 post). Power Pack Kit £2.10.0 (4/- post;. Cabinet (tee
ilMttration) 50/- post paid or £14.10.0 the three items pott paid. Parts List Booklet
and loll detallt 1/8 (Eree with kit). A.E.I. Circuil of 14 Trantistori; SW per Channel
Into S to 15 ohm Speaker. 50m V input. Ceramic. Crystal Cartridge, Radio Tuner or
Output from Tape Recorder may be need. 20 to 20,000 Hi ± 3dB. Neg. Peed Back
1MB. 12Jn. X Sin. high X Bin. Cabinet, Clr-Eit Board Construction. Bass. Treble
and Vol. Control, lor A.C. mains of 200-250V. Bast Cat and Lilt; Treble Cut and
Lilt, rally built 13 extra. Delivery by return ol post.
66 ELMS ROAD
ALDER SHOT, HANTS.
Alderebot 22240
CATALOGUE Sd.
GLADSTONE RADIO
(2 mine, from Station and Buses.)
CLOSED WEDNESDAY AFTERNOON
BAKER MAJOR £8
The remarkable quality and performance
of the "Major" makes possible truly
brilliant and rich sound from a single
loudspeaker. It recreates the entire
musical spectrum from 40 to 14,500 c.p.s.
The unit const tt» of the latest double
cone, woofer and tweeter cone together
with a special Baker magnet assembly
Alcomax II having a flux density of
14,000 gauss and a total flux of 145,000
Maxwells. Bass resonance 45 c.p.i.
Plated 20 watts. Voice coils available 3
or 8 or 15 ohms. Price £8, or Module
version as illustrated with tweeter,
crossover and baffle, £10.19,6,
Baker Reproducers Ltd
Bensham Manor Road Passage, Thornton Heath, Surrey. 01-684 Io65
4fl page Enclosure
Manual 5/9 Pose Paid.
rk
WKAH $0 PGOFCSStOAfAL Ttf£
S££F'%Y^Sik YW&W A£ROSOL WAY-
— - #
M/AU/7 HP BLACK WRWKCe
WOW! OR (CRAC K Ce) f;„; s h e$
Yukan Aerosol spray tit contains 16 oats- fine quality, durable easy instant
spray. No stove baklnj required. Hammers available in jriy, blue. gold.
bronie. Modern £j|ihe'l Black Wrinkle (Cut lie) ill at M/ll it our
counter or 15/1 I, carriage paid, per push-button lell'lpny cm. Also
Durable, hoc and water resistant Black Mitt finish (11 on self-spray
tins only) 13/11 carriage pile.
SPECIAL OFFER: I can plus optional transferable inap-on irini'Aiii:!:
(value 5/-) for 18/11. carriage pud. Choice of 13 Sill-iprty plain celourc
and primer (Motor cir quality) alio available. .-_-- --.
Plane ant ota cheque or crossed P.O. for total amount to; l£Z~-
YUKAN, DEPT.PE76 307*. EDGW ARE ROAO, LONDON. W.2.
Wt tuppl y many C ov* r n men t De pi rtmen ti. Mu nici pal Aucno ri tin. tnstitu cu
and Leading Industrlil Organisations — We can jupply you too,
I Op« n all day Saturday, Closed Thursday afternoons, eeeeae
.■San a !-',■''
corr.peid
ZrfK Cntwndte
Citat loceuer
Mttolt'ci Ccr Slut.
tVonie ffrtO Gold-
384
VALUABLE NEW HANDBOOK
ID AMBITIOUS
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"ENGINEERING OPPORTUNI-
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NEW! SOLID STATE HIGH FIDELITY EQUIPMENT British made
POWER AMPLIFIERS— PRE- AMPLIFIERS— POWER
G I idpi i crc W a proudly preie nt this new range ol Audio Euuipment developed irom Dinsdale
OUrrLI to jf]t, tl — each unit or system will compare favourably with other professional
equipment jelling at much higher prices. Briet detail) are below: —
iwnrnK.-sir »■
W m ft # m
— — - -
^ MF3
SP6-2
■ DUO VTffTI IrYMO —
.a- .._. „ r: — — •
iiir-iii- -ii4'- ~'dk" -ii- *>^
•W 1 -ta- .-an- HR -it- «5r— • 1 9
J^-
COMPLETE FULLY ILLUSTRATED
BROCHURE FREE ON REQUEST 11 and 21
V
■J>
Syitcm Compriting Price
•
A
5 watt mono lor /III 1 A
3/S ohm speakers * ■ V.JM
•
1
12 watt rnooo lor /|7 l-l £
3 to 5 ohm ipeaken *■ ■ ■** ■ * ■<?
•
2
IS watt mono lor /|i n /
IB to 18 ohm speakers 61*1. IX. O
•
4
24 watt mono two channel lor /1ft 1 C ft
18 to IS ohm ipeaken t AW, 1 3 .U
*
Q ! 20 watt mono.stereo lor it A A A
O is to 16 ohm speakers WiMM
O 2* watt mono/stereo for f ?£ 1 C 11
7 8 to 6 obo retaken MW. 1 3.W
M 40 watt mono, stereo for f)<t [flft
1 ^ 7! to la ohm ineskers W7.ll/iU
-
MANY OTHER SYSTEMS AVAILABLE
Send lor loll detail!
THE FINEST VALUE IN HIGH FIDELITY - CHOOSE A SYSTEM TO SUIT YOUR NEEDS AND SAVE POUNDS
VHP FH TUNER
87/105 Mc/9 Transistor Superbet. (Joared
tuning. Terrific quality and sensitivity.
For valve or trai»*i&tor amplifiers. 4 N x' ; K
'Jiin. Complete with dial plate. 5 Mullanl
Transistors, Plus 4 Diodcs.
AiL lor Brochure 3
TOTAL COST
TO BUILD £6.19.6 '•*■*'«
FH STEREO DECODER Brochure 4
7 Kullard Transition. Printed Circuit
Design with Stereo Indicator. For use with
my valve or traosistor FH. Uses pot
cores to Hullard design and iter, and silicon
transistors. As used by BBC. and G.P.O.
Complete Kit Price £5^ | Qq P.P. 2,6
BUILD A QUALITY TAPE RECORDER with MARTIN RECORDAKITS
383 DECKS* .
* TWO-TRACK. link £10.10.0. Amplifier.
£14,18.6, Cabinet ami -speaker 7e;ns. Complete
kits with microphone Tin. 1 .200 It. tape, apare
spool.
Today's Value £4&. 29 gns. PP. 18,9
* POCK-TRACK. Deck £13.10.0. Amplifier
£16,18,6. Cabinet and epcaker 7 ens.
Complete kits with microphone Tin. 1.200ft.
tape, spare spool.
Today's -i<* _
Value £50 SI gtlS. P.P. 18/6
\€>
m
Ask tor Brochure 5
MW LW 80ALITY
TRANSISTOR RADIO TUBES
Fully tunable superbet with excellent sen-
sitivity and selectivity. Output up to
i volt peak. Complete with Iront panel,
etc. 9 volt operated. For use with any
amplifier or tape recorder.
TOTAL COST
TO BUILD £3. 1 9.6 p - p - B ' 8
TRANSISTORS - SEMICONDUCTORS
COMPLETELY NEW 1968 LIST OF 1000
typqs available from stock. Send for
your FREE COPY TODAY. (List No. 36)
• S.C.R's from 5/-
■sr FIELD EFFECT TRANSISTORS from 9/4
-k POWER TRANSISTORS from 5, -
* DIODES AMD RECTIFIERS from 2/-
24 page Illustrated Brochure as above includ-
ing Valves and Quartz Crystals. 1 - post paid.
GARRARD DECKS
all the LATEST MODELS
COMPLETE
RANGE IN
FROM £5.19.6 STOCK
Send lor illustrated Brochure 16 ft 17
I<l T AL£ 0ST T0 BUILD 99 GNS.
r Build this instrument stage by stage In your own hor
A truly portable instrument lor all enthusiast*.
ELECTRONIC Art for brochure ?
Also READY BUILT AND
TESTED 128 gns.
Deferred terms
available.
DEPOSIT £36.8.0 and 12
monthly payments of
£9. Total £144,8.0.
KIT ot PARTS Deterred
terms: — DEPOSIT £29,18.0
12 monthly payments ot £7.
TOTAL COST £113,19.0.
ORGAN COMPONENTS
We curry a comprehen-
sive stock of organ cum*
portents for TRANSISTOR
AND VALVE FREE
PHASE desigus. Brochure 10
EXPORT PRICES
Build the PRACTICAL ELECTRONICS
FLUORESCENT CAMPING LIGHT
AS DESCRIBED IN MARCH.I966 Edition
Total Cost including Construction Data
Less Metal work pai/ POST
and Tube >"/0 2/6
All items ovo/loofe separately
ASK FOR PARTS LIST No. 43
TRANSISTOR CAR RADIO
Send tor Brochure 15
(qI^Ji
British Hade G-Transistor MW/1W.
IS volt 3 watt output. Push-button
wove- change. Supplied built, boxed, ready
to use with Speaker anal Haiti.'. Car
fixing kit and iitnnu,facliirers" current
guarantee. Special Bargain Offer. Positive
or Negative Earth.
5 Fush-bultoo ifc-luxc (Q I Q Z P.P.
or — Earth
i a
7-TRANSISTOR
MW-LW SUPERHET
PORTABLE
NEW!
New pi'iutud circuit design with full power
output. Fully tunable on both mw/lw
bands. 7 Transistors plus diode, pusfa-
pull circuit. Fitted 5 inch speaker, large
fertile aerial and Milliard transistors. Easy
to build with terrific results, AH local,
and continental stations. Siic 10 <7X3Jin.
TOTAL COST
TO BUILD £jk I 9.6 PP - 4;8
Send lor Brochure 1
NEW MODELS
TRANSISTORISED
Test Equipment
PRICE "ggf
Power Sopply £14.0.0 33
30 Audio Generator £19.10,0 34
31 R.F. Generator £18.10.0 35
32 C.R. Bridge £10.10.0 26
33 Inductance bridge £20.0.0 29
27 Signal Generator £10.10.0 14
66 Inductance bridge £13.0.0 14
Send lor descriptive illustrated Brochure.
All units POST PAID including Battery.
BUILD THE PRACTICAL WIRELESS
I.C. F.M. TUNER
AS PER DECEMBER, 1967 ISSUE
TOTAL OO I A POST
COST 1/6
Including R.C.A. CA3I04 Circuit and
Layout Diagrams. Parts List No, <tOA
BUILD THE PRACTICAL WIRELESS
SWITCHED F.M. TUNER
AS PER AUGUST. 1967 ISSUE
TOTAL fjit POST Parts List
COST f I JO 2/6 No. 39
I 1 With Circuit and Layout Diagrams.
PRACTICAL ELECTRONICS
GLiSSANDOVIBE
85- P °6 ST
AS PER FEBRUARY. 1968 EDITION
Parts List No. 42
CATALOGUE
LATEST EDITION
240 pages, 6,000 items
1,000 illustrations
-jV 25 pages of transistors and semiconductor
devices, valves and crystals.
•jt 150 pages of components and equipment.
■yV 50 pages of microphones, decks and Hi-fi
equipment.
The most comiirehcnslvc — Concise — Clear com-
ponents Catalogue in Gt. Britain, Complete
with 10/- worth Discount Vouchers Free with
every copy.
Send today 8/6 l°Z
1 itMiMim lit ^^
\M
-3^
tsju
^
..... m;
rfsyi 1 - n
•*■ Fully TRANSISTORISED POLYPHONIC. British deiicu. ON APPLICATION »- ■« a »s . _j , ^J..«*_ CDCC -_ _,._.. a»*
» Call in lor a DEMONSTRATION and see lor Toorse II. ^M ftrrLILHI IW1 f u ff (j e t a ,l s on advertised PfOQUCt? FREE Off reQUCSt
I HENRY'S RADIO LTD. CD
303 EDGWARE ROAD
LONDON, W.2
rtlONi:: 01-733 1008/9
Open Hon. to Sat. 9 a.m.-6 p.m. Tburi.
9 a.m.-l p.m.
WE CAN SUPPLY FROM STOCK
MOST OF THE PARTS SPECIFIED
ON CLRCDITS IN THIS MAGAZINE.
SEND LIST FOR QUOTATION.
-— — -~
