This is only a preview of the December 1988 issue of Silicon Chip. You can view 44 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Articles in this series:
Articles in this series:
Articles in this series:
Articles in this series:
|
I
I
How diesel-electric locos killed off steam
$3.50 DECEMBER 1988
NZ S4.95 ~Ng
High Performance In
Your Shirt Pocket!
3 l /2 digit LCD Display
Ranes
Max Res Accurac
Vdc
Vac
Ade
100µV
1mV
100µA
10mA
100µA
10mA
0.Hl
200mV-1kV
2V-750V
200mA
10A
Aac 200mA
10A
Ohms 200O-2Mf.l
0.5% + 1dig
0.75%+5dig
0.75%+ 1dig
1.5%+5dig
1%+5dig
2%+7dig
0. 75%+ 1dig
Display also has
Low Battery &
Over-Range
Indication
Built In Diode Check,
Lo-Power Ohms &
Continuity Test Beeper
Memory Function for
Relative Readings
(DM6235 & DM6335)
Autoranging
Manual Ranging
Over-Ride
(DM6235 & DM6335)
One Year Warrant
Hold Reading Function
(DM6335)
10A Range
Automatic
Current
Limiting
Overload Protected to
1000Vdc/750Vac
$88.80
$99.60
Look At The Low Pricesl
DM6135 Autoranging
3 1/2 digit 10A ac/dc
DM6235 As above
with Memory
function and Range Hold
Prices include 9V Battery and High Quality Silicon
Rubber Test Leads with Screw-On Alligator Clips
DM6335 As above
with Data Hold
l0MQ Input
Impedance
Gotta
Gatta
GoldStar
Dealer enquiries welcome. Call (02)736 2243
Recommended prices only including Sales Tax
$118 • 80
You 've Gotta Getts Goldstar from :
M.,L John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355
N.S.YI', Ames Agency 699 4524 • J Blackwood & Sons• George Brown 519 5855 Newcastle 69 6399
• Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebson 707 211 1
• Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Pty Ltd 698 4776
• Petro-Ject 569 9655 • David Reid 267 1385 • Digitel 709 6511 • Geoff Wood 427 1676
N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999
QUEENSLAND Auslec (07) 8541661 • G. Brown Group (07) 252 3876 • Petro -Ject (075) 91 4199
• St Lucia Electronics 52 7466 • Cliff Electronics 341 4655 • L.E.Boughen 369 1277
• The Electronics Shop (075) 32 3632
• Thompson Instruments (Cairns) (070)51 2404 • Nortek (Townsville)(077) 79 8600
S.AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688
• J Blackwood & Sons 46 0391 • Petro-Ject 363 1353
TASMANIA George Harvey (003) 31 6533 (002) 34 2233
VICTORIA Radio Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301
• A.W.M. Electrical Wholesalers• Petro-Ject 419 9377 • J Blackwood & Sons 542 4321
• Factory Controls (052) 78 822 • Mektronics Co 690 4593 • Truscott Electronics 723 3094
W AUSTRALIA Atkins Carlyle 481 1233 • Dobbie Instruments 276 8888 • Protronics 362 1044
DECEMBER 1 988
THIS IS THE VIEW inside our
rugged new 120W public address
amplifier. This month, we
describe the circuit and show
you how to assemble the PCBs.
See page 26
FEATURES
4 Electronics & Holden's V6 Engine by Leo Simpson
The end of the distributor
18 Harman Kardon P~665Vxi Amplifier by Leo Simpson
A high power, high current design
42 Kit Clinic & the 1 00W Power Module by John Clarke
How we solved one reader's problems
76 The Evolution of Electric Railways by Bryan Maher
Pt.14: Why diesel-electrics killed off steam
PROJECTS TO BUILD
WANT REALISTIC SOUND
effects for your model railroad
layout? Our new diesel sound
generator has all the desired
features. Construction starts on
page 50
26 120 Watt Public Address Amplifier by Bob Flynn
The microphone preamplifier and mixer stages
34 Simple Car Antenna Adaptor by John Clarke
Use your rear window demister as an antenna
50 Build a Diesel Sound Generator by Greg Swain
The sound follows the locomotive
SPECIAL COLUMNS
14 Vintage Radio by John Hill
Restoring the dial mechanism
44 The Way I See It by Neville Williams
Would you please pass the salt? I need a few grains
62 Serviceman's Log by the original TV serviceman
The customer has no idea
70 Amateur Radio by Garry Craft
Simple SSB adaptor for shortwave receivers
OUR INTREPID SERVICEMAN
this month battled both the set
and the customer. His
frustrations with both begin on
page 62
DEPARTMENTS
2 Publisher's Letter
3 Mailbag
59 Circuit Notebook
83 Subscription Page
84 Product Showcase
90 Ask Silicon Chip
92 Back Issues
96 Market Centre
96 Notes & Errata
FED UP WITH REPLACING
you car radio antenna? This
gadget will let you use your rear
window demister instead. We
show you how on page 68
DECEMBER 1988
1
SILICON CHIP
Publisher & Editor-In-Chief
Leo Simpson, B.Bus.
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Advertising Manager
Paul Buchtmann
Regular Contributors
Neville Williams, FIREE, VK2XV
Bryan Maher, M.E. B.Sc.
Jim Yalden, VK2YGY
Garry Cratt, VK2YBX
Jim Lawler, MTETIA
John Hill
David Whitby
Photography
Bob Donaldson
Editorial Advisory Panel
Philip Watson, VK2ZPW
Norman Marks
Steve Payor, B.Sc., B.E.
SILICON CHIP is published 1 2 times
a year by Silicon Chip Publications Pty Ltd. All material
copyright (c). No part of the contents of this publication may be
reproduced without prior written
consent of the publisher. Kitset
suppliers may not photostat articles without written permission
of the publisher.
Typesetting/makeup: Magazine
Printers Pty Ltd, Waterloo, NSW
2017.
Printing: Masterprint Pty Ltd,
Dubbo, NSW 2830.
Distribution: Network Distribution
Company.
Subscription rate: currently $42
per year (12 issues) inside
Australia. For overseas rates,
refer to the subscription page in
this issue.
Liability: Devices or circuits
described in SILICON CHIP may be
covered by patents. SILICON CHIP
disclaims any liability for the infringement of such patents by the
manufacturing or selling of any
such equipment.
Address all mail to: Silicon Chip
Publications Pty Ltd, PO Box
139, Collaroy Beach, NSW
2097. Phone (02) 982 3935.
ISSN 1030-2662
• Recommended and maximum
Australian price only.
2
SILICON CHIP
PUBLISHER'S LE'1·1'ER
End of volume one;
start of volume 2
Every month the production of SILICON CHIP is a matter of following
a tight schedule as all the various articles are prepared, written,
typeset and laid out. It's a lot of work as you might imagine but most of
it is largely routine; it has to be that way to keep to the schedule. Some
tasks are not routine though, especially if they have not been done
before.
One such task this month was the preparation of the index for our
first volume which spans 14 months, from November 1987 to this
month, December 1987. Inevitably, the preparation of an index must
cause a review of what has been done in the past and when we look
back it is with a certain amount of satisfaction.
Our · first volume contains over 1000 editorial pages, with an
average of around 600 words per page. That adds up to over 600,000
words and millions of keystrokes to prepare the editorial material.
There are hundreds of diagrams, photographs and cartoons and, of
course, the core articles which are our constructional projects. All
told, there were over 60 constructional projects, with some running
over more than one issue.
·
The numbers merely emphasise the large amount of work which has
gone into SILICON CHIP. All this work would be for nought though, if it
was not for the large amount of positive feedback we have received
from you, the readers, in literally thousands of letters. These have
been very encouraging.
In the first few months after we launched SILICON CHIP a number of
readers expressed doubts as to whether we could maintain the high initial standard. Now, there seems to be general agreement among
readers that not only have we maintained the standard, we have improved it. Thank you to all those who have written in with constructive
criticism. We are striving to do even better.
We have some great projects planned for the new year. Some of
these are already finished and are merely waiting for the day when
the semiconductor companies can supply production ICs. In fact, that
is one of the traps in using new semiconductors in our constructional
projects. Sometimes the devices are so new that the semiconductor
manufacturers have yet to put them into full production. Innovation
sometimes has its price.
When all is said and done though, we look back upon our first year
as having been an enjoyable challenge. We look forward to our next
year with great anticipation.
Leo Simpson
MAILBAG
Noisy motors in model locos
After reading your article in the
April issue of SILICON CHIP on the
W alkaround Throttle for Model
Railroads, I purchased a kit from
Jaycar.
Although I know little about electronics I found it very ~asy to put
together due to your excellent
diagrams and explanations. After
overcoming a minor problem, it worked and did everything it was supposed to except I had motor growl.
Then, in the June issue, I read
where a reader from WA asked how
to change the pulse frequency. I
followed your suggestions but the problem is still there.
I've had my controller checked out
by an electronics technician and he
confirms that I have everything
where it should be, so I'm hoping you
could throw some light on how to
overcome this growl.
My layout has taken a back seat for
a few months and now I would like to
blow the dust off and give it another
go. Thank you for an interesting
magazine.
Chris Simons
South Melbourne, Vic
Comment: Motor 'growl" is a
characteristic of pulse power control,
so your unit is working as intended.
For further details, see our answer to
another reader in the Ask Silicon Chip
pages.
Optical tachometer danger
Your May 1988 magazine has an
optical tachometer project to build
which, I have no doubt, is excellent in
· itself.
As a state qualified instructor in
the sport of flying model aeroplanes
by radio control, I would point out to
you the danger of tuning an engine
from in front of the propeller.
This is lesson 1 (often repeated) until a beginner learns to start an
engine at low throttle and move
behind the propeller before opening
up or removing the glowplug connection or adjusting the mixture.
Your photographs clearly show someone at risk if a propeller breaks.
With a tip speed in the vicinity of 150
to 200 metres per second, you don't
have time to duck.
Also if the helper loses grip on a
vibrating, generally slippery surface
and the aircraft surges forward, the
prop would make short work of the
tacho and possibly the hand holding
it. (A modern 10cc standard engine
develops 1.8HP, a competition engine
3HP or more).
For the competition flyer, ground
running rpm is not the only indication
of correct tune. Perhaps your contributors could come up with an
adaptation using a cheap microphone
insert to acoustically measure rpm.
With the advent of ducted fans
there is no access to a rotating part.
This could also be used to determine
rpm in flight, at a point perpendicular
to the line, as this is of more interest
to a competition flyer than ground
rpm. A switch could be added to
select either 4-stroke or 2-stroke.
Stephen Vickers
Denistone, NSW
Comment: Yes, there is some risk in
the procedure we show but no more
risk than occurs during starting or
throttle adjustment.
Smell of an oily battery
All of us who fiddle with and think
about small battery powered electronic devices are constantly trying to
squeeze the desired functionality into
the minimum possible volume. During
my experience with pagers a couple
of years ago, I was continually amazed at the performance the Japanese
could get out of a single AA-size
penlite battery.
I think a lot of professional and
amateur readers would be interested
in:
(1). A review piece along the lines of
the miles/gallon marathon which
perhaps looked at highly efficient
battery-powered DC-DC power converters. I am thinking specifically of
pagers, watches, digital thermometers, digital display vernier
calipers, and digital humidity and pH
meters etc.
(2). A construction project which offered a design for a single AAA or AA
battery source which could be efficiently stepped up to 5V, 6V, 9V or
12V DC. This could cover a lot of
home and mobile electronics applications (both analog and digital).
SILICON CHIP,
PO Box 139,
Collaroy Beach 2097.
Maybe it could be run as a competition to see how far a little "mouse" or
"carriage" could run on a single
fresh battery on a flat surface.
Ian Rowatt
Koolewong, NSW
Wants TV reception on
FM antenna
I have just purchased the October
issue of SILICON CHIP and it is yet
another fabulous issue. I particularly
liked the 5-element FM antenna article by Leo Simpson and Bob Flynn.
I would be interested to know if the
antenna could be used to pull in a
good signal for ABC Channel 2. I have
little knowledge of technical radio,
however I do recall ABC TV being on
(or near) the FM waveband and I
wonder if the antenna would be
suitable for this purpose.
Samuel Venning
Port Melbourne, Vic
Comment: The FM antenna was not
designed for TV reception although it
should perform well on channels 3 and
4. For channel 2 reception you would
probably get better reception from a
3-element Yagi cut specifically for the
job.
Project suggestion
As a very keen fisherman there is a
project I would like you to consider one which would not only be appreciated by fishermen but by all people who "go down to the sea in
ships". I am referring to a "tide
clock".
The tides on the east coast are approximately 24 hours & 50 minutes
from one tide (high or low) to the corresponding tide the next day (eg, from
high to low to high to low to high).
There are a number of commercial
units available but cost from $110.00
to $185.00. Most use a quartz movement that has been adjusted to give
one complete rotation of a single hand
every 12 hours and 25 minutes.
The more elaborate types show
both actual time and tide time but I
feel a single hand showing the tide only would be sufficient. I hope you can
develop such a project.
J. Harvey
Port Macquarie, NSW
DECEMBER
1988
3
By LEO SIMPSON
Released on to the Australian market only
a few months ago, the Holden VN Commodore
represents another stage in the integration of
electronics into automobiles. It is a large car with
a big motor but electronics enables it to give a high
level of performance with improved fuel economy.
It must come as a surprise to
many people to learn that the new
VN Commodore has the biggest six
cylinder motor ever fitted into a
Holden. It is a whopping 3.8 litre
V6. As you might expect, it offers
sparkling performance but it is
lighter and more compact than
previous Commodore engines and
4
SILICON CHIP
gives better fuel economy.
The reason it does give better
fuel economy is because of electronics, in the engine management
system and in the ignition system.
General Motors has certainly
had its ups and downs in recent
years in the Australian market.
Some years ago, rather than spend
the money to develop an improved
engine, the company committed
itself to using the Nissan 3-litre fuel
injected engine. This was featured
in the VL Commodore.
Unfortunately, the relative movements of the Australian and
Japanese currencies then made
that engine far too expensive.
Holden's new 3.8 litre V6 motor does not have a distributor or
conventional ignition coil. Instead, it uses Direct Fire Ignition, a system
with no moving parts. Three double-ended coils, mounted on a module
at the front of the engine, fire the six plugs directly.
General Motors then had to find a
cheaper engine but one with at
least equivalent performance to the
Nissan unit. Fortunately, they were
able to use one employed in the
compact American Buick.
This 3.8 litre V6 unit had
originally been cut down from a
larger VB and in its first version
had been a rough running engine.
This was because the angle between the cylinder banks was 90°
whereas 60° is the ideal angle for
a V6. This rough running was one of
the reasons that General Motors
had not originally adopted it for
Australia.
Fortunately, a later model of the
engine incorporated a balance
shaft, similar to that first used on
the Mitsubishi Sigma 4-cylinder
engine, and this led to very smooth
running.
The engine is now being assembled in Australia, from American
parts, although the inlet and exhaust manifolds are made here.
Engine installation
The engine bay of the new
Holden Commodore is notably clean
and uncluttered. This makes a pleasant change from the "chock a
block" installations on most modern
cars with their complex plumbing,
multiple belt drives for all the accessories and a huge air cleaner
hiding it all.
Since the V6 engine is so short, it
sits well back in the engine bay,
which incidentally leads to improv-
DECEM BER 1988
5
--
+12v------.
CONTROL
CIRCUIT
CAPACITOR
POINTS+
.,.
Fig.1: a conventional transistor switched
ignition system uses one coil and a distributor.
The plugs are negatively polarised to lower
the required firing voltage. The arrows show
electron current flow.
ed weight distribution in the car.
Apart from its more compact size
though, there are several reasons
why the V6 looks less complicated
and cluttered than engines in other
modern cars.
First, it uses direct fuel injection
into each inlet port so instead of a
complicated multibarrel carburettor there is a simple throttle body
(containing a large butterfly valve
linked to the accelerator pedal).
The throttle body is linked via a
large diameter duct to the aircleaner which sits on the righthand
side of the engine bay.
Second, it uses a long "serpentine" belt to drive the accessories
rather than the multiple belts used
in other cars. The one long belt
drives the water pump, alternator,
power steering pump and airconditioning compressor. The
radiator fan is electrically driven
and controlled by the engine
A Hall Effect sensor and magnet
system generates timing pulses from
these toothed wheels mounted behind
the harmonic balancer.
6
SILICON CHIP
Fig.2: this diagram shows one of the three
coils in Holden's Direct Fire Ignition.
Each coil simultaneously fires two plugs,
one with positive polarisation, one with
negative polarisation.
management system which we'll
talk about later.
Third and perhaps of most interest to readers of SILICON CHIP,
the usual ignition coil and distributor is not present on the V6
engine. Instead, it uses a new computer controlled ignition system
with no moving parts at all. General
Motors call it "Direct Fire Ignition"
(DFI} and it is made by their AC
Delco division.
Direct Fire Ignition
Commodores have had solid state
ignition systems since 1980 while
more recent models such as the VK
and VL had electronic spark timing
(EST) via sensors mounted on the
flywheel. However, they still
employed a more or less conventional ignition coil and HT distributor.
In the new model with V6 engine,
all that has gone out the window
and is replaced by a system which
is housed in one module adjacent to
the alternator. All six spark plug
leads plug into this module. Its
workings are quite different to conventional transistor switched ignition systems.
Inside the module are three
double-ended ignition coils, each
driving two spark plugs. Each pair
of spark plugs is fired simultaneously by its associated coil
which means that while one plug
fires at just before TDC (top dead
centre) for the power stroke
another plug fires at just before
TDC for the exhaust stroke.
This brings up a number of in-
teresting points. In a conventional
ignition system, as shown in Fig.1,
the spark plug is polarised so that
its centre electrode is negative with
respect to the outer core. In this
way, the voltage needed to fire it is
reduced by 30 % compared to the
alternative connection whereby the
centre electrode is positive.
Spark plugs in series
This situation cannot be obtained
in the Commodore V6 though,
because of the double-ended ignition coils. The circuit configuration
is as shown in Fig.2. Effectively, the
coil secondary is connected in
series with the two spark plugs.
One plug is fired with the "correct"
negative polarisation as in a conventional system while the other
plug has positive polarisation of the
centre electrode.
In practice, this makes no difference to the reliability of the ignition since the coil has more than
enough secondary voltage to fire
both spark plugs. Open circuit
voltage is more than 40,000 volts.
The only real consequence of the
differing polarisation for each pair
of spark plugs is that after a long
period of use, those plugs with
negative polarisation will have erosion of the centre electrode while
those with positive polarisation will
have erosion of the outer electrode.
Even this is of no importance
since General Motors recommend
that the spark plugs be replaced
after 15,000 kilometres. After this
period of use they will have negligible wear but the additives in lead
vance or centrifugal advance
system. All the engine timing information comes from the main electronic control module (ECM) which
performs all the engine management functions. However, the ECM
still requires basic timing information to derive the spark timing.
On previous Commodores with
electronic spark timing, this information was derived from a sensor
driven by magnets on the flywheel.
On the V6 motor, timing pulses are
produced from a double Hall Effect
sensor which monitors concentric
toothed rings on the harmonic
balancer (at the front of the engine).
The outer ring has 18 equally
spaced teeth while the inner ring
has three "windows" of differing
length at 120° intervals. The electronic control module determines
the crankshaft position by measuring the number of voltage transi
tions from the sensor on the
18-tooth ring during the period the
other sensor "sees" a window on
the inner ring. This crankshaft position information is fed from the DFI
module to the ECM which then provides precise timing of the three ignition coils.
0
The electronic control module (ECM) uses surface mount custom
microprocessor and co-processor ICs. The specially programmed EPROM
module to suit it to the V6 engine is mounted on a socket at the bottom.
Engine management
Electronic instruments are used in the Commodore Calais. This is the back of
the instrument panel showing the flexible printed wiring and three sockets for
connection to the harness.
free petrol (to replace the lubrication effects of lead tetra-ethyl)
eventually cause contamination of
the ceramic insulator which encloses the centre electrode.
This contamination will lead to
plug misfiring, hence the recommendation to replace plugs at
15,000km intervals.
Claimed advantages of the AC
Delco Direct Fire Ignition include
no moving parts, less maintenance,
no mechanical load on the engine,
elimination of mechanical timing
adjustments, more coil down time
between sparks, and more time
available to allow the ignition coils
to saturate.
As in previous Holden Commodores, there is no vacuum ad-
Having explained how the double
Hall Effect sensor monitors crankshaft position, we can list the other
parameters monitored by the electronic control module. They are
listed as follows:
• Engine speed;
• Manifold absolute pressure;
• Manifold air temperature;
• Engine coolant temperature;
• Throttle position;
• Exhaust gas oxygen content;
• Battery voltage;
• Park neutral switch position;
• Vehicle speed;
• Air conditioning 'on' or 'off';
• Engine detonation (using a
knock sensor);
• Cranking signal;
• Auto transmission sump temperature;
• Auto overdrive clutch 'on' or
'off'.
With continuous monitoring of all
the above parameters, the ECM
controls the ignition system, as
already mentioned, as well as the
following systems:
DECEMBER 1988
7
to 1 by monitoring the signal from
an oxygen sensor mounted in the
exhaust manifold and then optimising the amount of fuel fed via the
solenoid-operated fuel injectors .
In electronic terms, the engine
management system is therefore a
"closed loop" feedback system
although at times it does operate in
"open loop" mode. This can happen
during idle, deceleration and
starting.
The electronic control module
uses a custom microprocessor in
conjunction with a a 16-bit
coprocessor and 16K of random access memory. The module is the
same as fitted to the current Group
A Commodore V8, the JD Camira
and the LD Astra/Pulsar series. It is
customised to suit the V6 engine
with a plug-in ROM (read only
memory) module which General
Motors refer to as a "Mem Cal"
unit.
Inside the cruise control module: on the left is the stepper motor which
operates the throttle valve while at right is the microprocessor and stepper
motor drive circuitry.
The zirconia element oxygen sensor screws into the stainless steel exhaust
manifold to provide feedback signals for the engine management system.
It generates an output voltage at temperatures above 360°C.
•
•
•
•
8
Fuel system, consisting of the
fuel injectors and electric
fuel pumps;
Idle air control;
Auto transmission torque converter clutch;
Air conditioner compressor
clutch;
SILICON CHIP
• Radiator fan;
• Diagnostics.
The major purpose of the electronic control module (ECM) is to
control exhaust emissions while
maintaining good driveability and
fuel economy. The ECM maintains
the air/fuel ratio at precisely 14.7
Information sensors
We've already talked about the
Hall Effect sensor and toothed rings
on the harmonic balancer. As well
as providing the crankshaft position information for ignition timing,
they also provide a measure of
engine speed (RPM) for engine control as well as a signal for the
tachometer which is an option on
some vehicles.
Let's now describe some of the
other sensors. To obtain a measure
of air flow in the inlet manifold, the
V6 has a solid state pressure
transducer. It also has a temperature sensor which is a negative
temperature coefficient thermistor.
At low temperatures it has a high
resistance (around l00kO at
- 40°C} while at high temperatures
it has a low resistance (around 700
at 130°C).
The throttle position sensor is a
potentiometer connected to the butterfly valve on the throttle body. As
with most of the sensors in the V6, it
is fed with + 5V from the engine
control module. The output of the
throttle position sensor is zero at
idle (when the butterfly valve is
completely closed) and it increases
to + 4.5 volts at wide open.
The detonation sensor detects
engine knocking. It is based on a
vibration sensor (accelerometer)
which puts out a voltage when it
<at>HITACHI
20MHz/lmV
$830
ExSa!esTax
$996 me tax
·
■·
Wouldn't you pay a bit more for
features like this?
So good we give the full Spee!
Display
CRT
Graticule
Accelerating
Potential
External Intensity
Modulation
Vertical Deflection
Sensitivity
Bandwidth
Rise Time
o
Quality Hitachi engineering
O Two year Warranty
o Includes two quality Hitachi probes
o Tough all metal case and front panel
o Ideal for servicemen - small footprint and
light weight (31 Ox370x130mm 6kg)
o Extensive triggering facilities including TV
sync and vertical mode for steady traces
when input frequencies differ widely
o Free 55 page operating manual with
circuit diagram
MAX. Input Voltage
Input Coupling
Input Impedance
Display Mode
CHl Vertical
Signal Output
X -Y Operation·
Sensitivity
Bandwidth
Phase Difference
Horizontal Deflection
Sweep Time Range
Trigger
Trigger Mode
Trigger Source
Trigger Sensitivity
Order now. Call
(02) 648 5455 32 Parramatta Rd, Lidcombe 2141
Fax (02)6471545 TelexAA24949 P.O.Box14Lidcombe2141
Melbourne (03) 480 0111 72-74 Chifley Drive, Preston 3072
Adelaide (08) 354 0588 Brisbane (07) 277 4422
Perth (09) 325 9333
Sydney
( BELL ]
Bell Test &
Measurement
The measure of quality
A Division of Bell-lRH Ltd (inc in N.S.W.)
Prices subject to change without notice
6-inch rectangular.
Internal , 8 x 10 div (1 div = 1 cm), Horiz onta l and
vertical center lines further marked in 0.2 div
increments, mark ing for measurement of rise tl me
Trigger Coupling
Trigger Slope
Calibrator
Power Supply
Ambient Temperature
Dimensions
Weight
MTBF
Accessories Supplied
2 kV.
Voltage : 5V o r more.
Effect ive bandw idth : DC to 2 MHz.
Max . inpu t voltage: 30V (DC+ AC peak }.
5m V/di v to 5V/div in 10 calibrated steps ± 3%.
lmV/div, 2mV/d iv ± 5% when using
x5 magnifier.
Uncalibra ted co nt inuous control between steps
1 : < 2 .5.
DC t o 20 MHz 1-3 dB }.
DC to 7 MHz (- 3 dB) when using x5 magnifier .
17.5 ns.
50 ns when using x 5 magnifier .
300V {DC+ AC peak) or 500Vp-p AC at 1 kHz
AC,GND, DC.
1Ml1 approx. 25 pF.
CH1, CH2 {n ormal o r invert). ALT. CHOP , ADD
Voltage : appro x . 20mV / div in t o 50!1
Bandwidth : 50 Hz t o 5 MH z (-3 dBi i nto 50!1.
CH1 : X -a xi s. CH2 : Y -a xis.
5m V/div to 5V /div.
lmV/ div, 2m V/div w hen using x5 magnifier.
DC t o 500 k Hz 1- 3 dB ).
3" or less from DC to 50 k Hz .
0 .2 µs/ div t o 0.2s/div in f9 calibrated steps ±3%.
100 ns ± 5% w hen using x10 magnifier
(20 ns and 50 ns uncatib rated ).
Uncalibrated con ti nuous co ntrol between steps
1 : < 2.5.
Automatic {sweep runs in absence of a triggering
signa l and for signal below 30 Hz), Norma l {sweep
runs when triggered ), TV' V, TV-H.
CHl, CH2, V -MODE. Ex ternal, Line.
20 Hz to 2MHz 12 MHz to
20MHz
I CH 1 an d CH 2 i
0 .5 di v
I 1.5 div I
20mV
I E,?C ternal
I
I 800rnV I
AC.
+ or Square w ave. Vo ltage: 0.5 V ± 3%.
Frequency: Approx . 1k Hz
Vol t age
: 100/ 120/220/240 V ± 10%.
Frequency : 50/60 / 400 Hz.
Power consumpti on : approx . 30 W.
Rated range of use : +10 to 35° C.
Limits of operation : 0 to 50° C.
Storage and transport : - 20 to 70°C.
310IW) x 130IH) x 370ID) mm.
12.2 X 5. 1 X 14.6 in .
Approx. 6 kg/ 13.2 lb.
20 ,000 hours for target value.
Two AT-l 0AJ 1.5 pro bes, Fuse , Power cable ,
Operation manual.
I
i
I
the electrical pulse fed to the injectors. This varies between O and 11
milliseconds and happens normally
once every crankshaft revolution.
Control modes
The compact V6 motor sits well back in the engine bay of the new Commodore.
It has an uncluttered appearance due to the use of fuel injection and
Holden's new Direct Fire Ignition system.
detects vibration at around 6kHz
with quite a narrow bandwidth of
500Hz. It is screwed into the lower
front side of the engine block.
If engine knocking (or pinging) is
detected, the ECM responds by
quickly reducing the ignition advance setting by 8 ° . When detonation stops, the ECM slowly restores
the original ignition advance
setting.
The addition of the knock sensor
is quite an improvement on the
engine management of previous
Commodores which had no way of
varying their electronic spark timing if knocking did occur.
The exhaust gas sensor is a zirconia element which is screwed into the exhaust manifold on the
lefthand side of the engine. When
the zirconia element is heated to
temperatures above 360°C, it produces a voltage at its tip based on
oxygen content, as compared to oxygen in the atmosphere.
The vehicle speed is monitored
by a 10-tooth wheel on the drive
shaft. The toothed wheel is
monitored by a Hall Effect sensor
and the pulses it delivers are fed
not only to the electronic control
module but also to the instrument
panel where they drive the analog
speedometer and odometer. In the
10
SILICON CHIP
Calais model, the odometer is based
on a non-volatile RAM (ie, a
memory which is not lost when battery voltage is removed).
Fuel control
The fuel system is based on
solenoid operated fuel injectors
made by Bosch. These are fed with
fuel pressurised at between 235
and 320kPa, as regulated by the intake manifold pressure. A high
manifold pressure, caused by a
wide throttle opening, results in a
high fuel pressure. A low manifold
pressure, which results when the
throttle is closed, gives a lower fuel
pressure.
In effect, the fuel pressure
regulator maintains a constant
pressure difference between the
fuel line and the inlet manifold. This
ensures that the fuel admitted by
the injectors does not vary according to manifold vacuum.
There are six injectors, located
directly in front of each cylinder inlet port. They act as control valves
and spray atomised fuel when they
are electrically pulsed by the ECM.
All six injectors are wired in
parallel and so they are pulsed
simultaneously. The amount of fuel
delivered for each engine revolution is controlled by the length of
We have already mentioned the
"closed loop" control mode
whereby the fuel/air mixture is
maintained at the optimum for best
working of the catalytic converter.
There are times though, when this
mode is not wanted, for example,
during cranking. At these times the
electronic control module works in
open loop mode.
In the starting mode for example,
the ECM ignores the signals from
the oxygen sensor and looks instead
at the coolant temperature, to find
out how hot or cold the engine is. It
then sets the injector pulse width;
ie, the length of time the injectors
are turned on for each engine
revolution. Depending on whether
the engine is hot or cold, the injector pulse length will be between 8
and 115 milliseconds.
If the engine is accidentally flooded with fuel, it can be started by
pushing the accelerator pedal all
the way to floor. The ECM then
pulses the the injectors for only 8
milliseconds every crankshaft
revolution, which has the effect of
clearing the excess fuel. The ECM
maintains this narrow pulse width
as long as the throttle is open more
than 98 % and the engine RPM is
below 300.
Once the engine starts, the ECM
remains in the open loop mode until
the following conditions are
obtained:
(1). The oxygen sensor has a varying output, indicating that the exhaust temperature is above 360°C;
(2). The coolant temperature is
above 44°C.
(3). Engine not at idle.
In the open loop mode the injector pulse width may well give an
air/fuel ratio of more than 14.7 to 1.
This can happen, for example,
when the engine is cold and needs a
richer mixture to drive without
stalling.
Acceleration mode
When high acceleration is called
for, the ECM notes the rapid change
in throttle setting and in manifold
The new Commodore has been completely tested to ensure electromagnetic compatibility for all its electronics.
pressure and provides extra fuel by
increasing the injector pulse width.
If extreme acceleration is called
for, the ECM may provide extra injector pulses during each engine
revolution.
During deceleration, the ECM
can cut off the fuel supply completely for short periods, giving improved fuel economy. Fuel cut off
occurs when all the following conditions are met:
(1). The coolant temperature is
above 56°C;
(2). Engine speed above 1500 rpm;
(3). Vehicle speed above 35km/h;
(4). Throttle is closed;
(5). Park/neutral input indicates
"in gear" (auto transmission only);
(6). Manifold pressure less than
20kPa.
If fuel cut off is in effect, the fuel
will be restored if any one of the
following occurs:
(1). Engine RPM drops below 1400.
(2). Vehicle speed drops below
30km/h.
(3). Throttle open at least 1 %.
(4). Manifold pressure more than
20kpA.
(5 ). Park/neutral input indicates
"in gear" (auto transmission only);
Fuel can also be cut off to protect
the engine against over-revving. It
cuts out for engine speeds above
5400 rpm and cuts back in again
when engine revs drop below 5000
rpm.
Battery voltage correction
Another interesting wrinkle to
the electronic control module is the
battery voltage correction mode. If
the battery voltage is low, the ignition system may deliver a weak
spark and the injectors may be
slower to respond to their short
pulses. The ECM compensates for
these potential problems by increasing the ignition dwell time, if
the voltage is less than 12 volts, and
increasing idle RPM and the injector pulse width if the voltage is less
than 10 volts.
Idle speed is something we
haven't touched on yet but the ECM
has control over this too, by varying
the opening of the electrically controlled "idle air control" which
bypasses the throttle valve when it
is closed. The idle air control valve
moves in steps from 0 to 255, corresponding to an 8-bit control
system.
Cruise control
A trip computer and cruise control are fitted as standard on the
Calais model and are an option on
other Commodore models. The
cruise control offers much the same
facilities as those on competitive
brands but it is of interest because
it does not use inlet manifold
vacuum to operate the throttle. Instead, it uses a stepper motor.
General Motors cite a number of
advantages in using the stepper
motor, among them being the fact
that the cruise control operation is
not affected by changes in engine
vacuum. In reality, since the cruise
control employs a microprocessor,
it is likely that the stepper motor
lends itself better to more precise
digital control.
Driving the Commodore
Part of the fun of preparing this
report was a short test-drive of the
car. Well, naturally the engine
starts and runs extremely well and
offers really sparkling acceleration. No doubt it will be the bestselling Commodore yet.
Now, how can we scrape up the
dollars to buy one?
Acknowledgement
Our thanks to Marc Mcinnes of
General Motors Holdens Automotive Ltd and to Jack Stepanien
for their assistance in the preparation of this report.
'~
DECEMBER1988
11
DIC
MITH
Give Yourself A
Christmas Present
.. .from someone who cares!
Includes bonus Mic. cat c-111&
Yaesu's Budget FT747GX:
IDEAL FIRST RIG!
S
1395
Everything you need without the frills! Yaesu recognised the fact that
amateur transceivers were getting out of the reach of the average person.
So they did something about it: the FT747GX.
A full 100 W with all amateur bands between 1.6 and 30MHz SSB CW
AM and optional FM; receiver is 100kHz to 29.9999MHz continuous'. If '
you're looking for value along with performance, there's simply not
a better rig than the FT-747GX: anywhere! Cat D-2930
Yaesu's
Top Ender!
Every amateur band from 50 to 1300MHz: that's some transceiver! It's
All the way ...
up to 1.2 gigs!
Yaesu's superb all band, all mode VHF/UHF FT736R. It comes complete
with the 2m and 70cm modules installed, you add the 6m or 26cm modules as you want them.
Crossbanding and satellite modes - inbuilt. In fact, everything you need
is there: IF shift and notch filters, wide/narrow IF filters for CW & FM,
VOX, RF Speech Processor, Noise Blanker, 3-stage AGC . . . you name it,
the FT736R has it.
s2999
FT736R with 2m & 70cm: Cat D-2920
25W Output
6m plug-in module: Cat D-2921 5599 (10 W)
26cm plug-in module: Cat D-2922 s999 (10 W)
(Introductory Price)
- Stocks due late December.
And the ultimate HF/VHF/UHF
transceiver:
fT767 GX
With BONUS Microphonsl
Combine the best features of the renowned FT757GX with the FT-726
and what do you have? The all band FT767GX. DC to light (well,
almost) covering all HF, VHF and UHF bands up to and including
70cm!
Sure, the FT767GX isn't cheap. In any sense of the word! It has all
the features and performance you'd want from your amateur station because it IS a complete amateur station - in one! Cai D-2935
Nothing extra to buy:
everytliing installed!
s4 750
Save aver $300!
• Every amateur band
between 160m & 70cm!
• A complete amateur station
in one handy package!
Bargain Antennas
Portability Plus/
FT-290Mkll
With BONUS ChargBr!
2M 5/8 Wave Vertical
Tinr 2M HandHelil.
Incredible
performance!!
2M portability, versatility and performance
at its best. The Yaseu FT-290 Mkll is just
what Santa ordered for real amateur value!
Features include All Mode (LSB, USB, CW
& FM), 10 memories, 2.5W
output, twin VFO's
and much more.
Yaesu's outstanding FT-23R puts into
Cat D- 2875 a hand held all the features that once
yllu'd need a monstrous bench model
$
to achieve. Full 144 to 148 band
coverage, 10 memories, fully
microprocessor controlled, repeater
WAS splits, high power and much more.
Cat D-3490
Inc. FNB-10 NiCd
875
s949
Battery holder extra
FT757GX II HF All Mode
Computer aided transceiver technology at its best!
There's no need for options with this one everything is built in ~all modes, all HF amateur
bands, AM/FM, 600Hz narrow CW filter, iambic
keyer, memory, 25KHz marker generator . .. the list
goes on! Cat D-3492
Value plus! Quality whip 1.34 metres. Uses standard
base. Cat D-4207
HF System Antennas
All approximately 2m long, appropriately loaded and
feature adjustable tuning.
SOM Cat D-4310
40M Cat D-4311
20M Cat D-4312
NOW 5469
Heavy Duty Antenna
Base
Up To 5 Watts
Output!
To suit HF Antennas above. Cat D-4313
Just
Save $20 and get up to 5 watts
output from your FT-23R with our
special offer on the FNB-11
600mAH battery pack. Available
with any FT23R purchase!
Save $20
.
s79
If ,eurchased
With FT-23R
NEW
Nearly $60
Valuef
Why go to all the expense of VHF when most of your
boating is close to the coast? Outstanding value and
performance makes the Sea Simba the obvious
choice. With 12 channels (10 fitted) including all
27MHz marine channels, 4 watts output, PA facility,
RF gain control, ANL, etc, etc. Cat D-1718
Only
s139ss
2m mobiles keep on getting smarter - and smaller.
The FT211 RH proves it: and it's versatile! You can
mount it overhead or under dash - and it gives 5 or
45 watts output on the entire 2m band. And this
month only, you'll save a massive $70. What a
great Christmas gift! Cat D-3494
5
1995
Limited Stocks
Due In Shortly!
s1495
12 Channel AM
Marine
FT212RH 2M FM TX
(Cat C-116o)
s3995
All only
Was$499
Cat D-3496
With BONUS
Microphone
s14ss
FREE with any Yaesu over $1001
729
5
High Quality and PBrformancBI
All Mode, HugB Savings/
FRG-9600 VHF/UHF
Receiver
What a way to start your Christmas shopping SAVE $200! The sensational FRG-9600 is the
ultimate scanner covering the complete 60 to
905MHz VHF/UHF spectrum. If ever you've dreamed
about all the features you'd like in a scanner then
this will make them a reality! Cat D-2825
Was $1199 Slashed to
s999
With BONUS ChargBrl
Bearcat 100XL
Scanner
Save $30 and get yourself a top
performing scanner to boot!
Features 16 channels, 9 band
coverage, auto/manual search,
selective scan delay, track tuning,
priority channel, direct channel
access .. . and there's more!
Covers 66-BBMHz, 136-174MHz &
406-512MHz. Cat D-2813
Reduced to
DSE AM CB
Superb quality and performance at the lowest
possible price! You won 't believe the features of this
compact DSE AM CB. Comes with all 40 channels,
full leQal power, built-in noise limiter, easy to read
LED display, mic, mounting hardware ... and more.
$
Cat D-1200
SaveS10
Exceptional
Value!
89
369
5
These pages represent just a
small selection of our amateur,
marine, CB & scanner range. For
the complete range, call into your
nearest Dick Smith Electronics
store today!
• NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 3871444 • Brookvale
(Warringah Mall) 905 0441 • Campbetltown (046)2 7 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill
439 5311 • Goslord 25 0235 • Hornsby 477 6633 • Liverpool 600 9838 • Maitland 33 7866 • Miranda 525 2722
• Newcastle 611896 • North Ryde88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777
• Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 • ACT• Fyshwick 80 4944 • VIC • Ballarat 31 5433
• Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366
• Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088
• Richmond 428 1614 • Ringwood 879 5338 • Springvale 54 7 0522 • OLD • Brisbane City 229 9377 • Buranda 391 6233
• Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863
• Toowoomba 38 4300 • T-nsvHle 72 5722 • Unde!wood 341 0844 •SA• Adelaide City 232 1200 • Beverley 3471900
• SL Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733
• North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977
5W 6 Channel
Hand-Held Marine
Superb 27MHz hand held transceiver from Uniden!
Features maximum legal power, all 6 channels fitted
with marine frequencies - there 's nothing extra to
buy! Plus you can connect it to your boat antenna
and power supply for maximum performance.
Cat D-1125
$20 OFF!! $
169
s&~Jm
VINTAGE RADIO
By JOHN HILL
Restoring the dial mechanism
Almost without exception, the dial mechanism
requires attention when restoring an old radio. The
dial is usually the focal point of the set, so every
effort should be made to restore it to original
condition.
There are three basic types of
dial drive: cord, gear and friction.
All give their fair share of trouble
but can usually be restored to asnew condition with a little care and
patience.
With the cord-drive type, the
cord either rots or wears through,
thus disconnecting the tuning knob
from the dial. The gear and friction
drive types are frequently made inoperative by corrosion, wear and
an accumulation of dust and grime.
These problems must be rectified if
a dial is to work smoothly once
again.
The best approach to any dial
problem .is to completely strip the
mechanism and thoroughly clean it.
A common cause of stiffness in the
mechanism is dried out grease on
the moving parts, particularly on
the track that the dial pointer slides
along. Unless the dial unit is properly cleaned, this stiffness problem
will remain.
Cord dial drives
In the case of cord dial drives, a
sticky dial pointer may cause the
cord to slip on the drive pulley. Proper cleaning really is important!
Cord dial drives can vary from
the simple to the annoyingly complicated. Some have cords and
pulleys running everywhere. One
particular model Radiola has four
pulleys, with the cord making four
passes across the front of the set.
This dial mechanism uses at least a
metre of dial cord.
The dial cord itself is a rather
special piece of string that has little
or no stretch in it. This is an important characteristic because if the
dial cord stretches with use, the
dial pointer will gradmilly shift its
relative position on the dial.
Unfortunately, genuine dial cord
seems to be unobtainable these
days and one has to make do with
substitutes. Although string can
often be used for the job, the results
are not usually very satisfactory.
Dacron fishing line is by far the
most suitable substitute for dial
cord and may well be superior to the
original cord. Many sports stores
sell Dacron fishing line and a cord
of about 0.5mm diameter is ideal.
Perhaps the best advice one can
offer regarding the restringing of
cord dial drives is to make a sketch
of the cord layout before removing
the old cord. Such a sketch can be
of great assistance and makes the
task of replacing a dial cord much
easier.
Gear driven dials
This huge full-width dial is from a post-war Kriesler console radio. The black
and white photograph does not do it justice for it is one of the multi-layer types
with a 3-D effect. Note the cast iron flywheel attached to the tuning spindle.
14
SILICON CHIP
Gear driven dials usually don't
give any trouble that a thorough
clean and a few drops of oil can't
cure, although there can be a few
minor rumbles in the gear train.
Most gear driven dials have a
backlash eliminator of some type or
other. This usually take the form of
a split gear that is sprung in op-
Vintage Radio
Kits & Parts
ORPHEIIS
*RADIO*
Gear driven dials don't usually cause much trouble hut should be given a
thorough clean-up and lightly oiled. The spring on the pinion shaft acts as a
backlash eliminator.
Suppliers of •
•
•
•
•
VALVES
RADIO KITS
CAPACIIDRS
RESISIDRS
BOOKS, ETC.
Please send for our free catalogue
ORPHEUS RADIO
RSD B98 BALLARAT
VICTORIA 3352
Ph. (053) 34 2513. Fax (053) 31 3412
FIX-A-KIT
Kit Repairs - $1 5 per hour.
Normal Rate - $30 per hour.
No charge for kits that can't be
repaired.
3 month Warranty on repairs.
Construction - fixed or hourly
rate .
1 2 Month Warranty on
Manufactured Kits.
This numbered gear driven dial is from the early 1930s and requires a lot of
work to restore the lettering to original condition. Dials with station markings
took over after about 1935.
posite directions. When such a gear
meshes with a normal gear there is
no backlash at normal operating
pressures.
It is important when restoring a
gear driven dial mechanism to
make sure that the backlash
eliminator is functioning properly.
It could be locked up solid with dust
or corrosion. When this is the case
the eliminator must be freed up if it
is to work as it was designed to smoothly and without backlash.
Friction drive dials
On the other hand, friction drive
dials can be very troublesome and
quite difficult to repair.
Most friction types consist of a
large semi-circular disc driven at
its periphery by a pair of small
spring-loaded driving flanges or
washers. These washers eventually
wear and this causes slip in the
drive mechanism. Most old radios
with friction dials will have slip
problems somewhere or other.
Custom Designing,
Manufacturing, Large or Small
Quantitites.
HYCAL
INSTRUMENTS
Design, Manufacture, Repair of
Electronic Equipment.
(02) 633 5897
(02) 92 6309
Fax (02) 925 0840
DECEMBER 1988
15
The dial glass
They don't make them like this any more - an ornate escutcheon from the
early 1930s. If only the rest of the set was still attached.
A "dial-a-station" dial from the· late 1930s. Like the pushbutton dials later
used in car radios, these novelty tuning devices gave trouble and were not
popular due to their additional cost.
Once again, a thorough clean of
the mechanism is an important first
step and could free up the works
enough to overcome the slipping
problem. Nothing could be more
detrimental to a friction drive
mechanism than to force it to
operate while all the parts are clogged up with dirt and corrosion.
The previously mentioned driving
flanges are usually the source of a
slipping dial problem. If the flanges
have not worn too much, they can
be reversed and the dial will be
good for years to come.
However, in many instances, the
16
SILICON CHIP
amount of wear both on the driving
flanges and the semi-circular disc
doesn't allow such an easy repair.
When this is the case, a pair of
slightly larger flanges are required
and these will grip the worn disc in
an unworn section and the dial will
work once again.
Friction drive dials often require
considerable modification to bring
them back to working order again.
If you have access to a lathe, you
can turn up special driving flanges
of any size as well as doing other
jobs that can get a radio restorer
out of trouble.
So much for the dial mechanisms.
Now for the dial itself - ie, the
glass plate with all the stations
marked on it. There are several
variations of the theme.
Vintage dials vary considerably
depending on their age. Early
mechanisms (up to about 1935)
usually have a numbered dial
graduated from Oto 100. The dial is
usually mounted behind a small
escutcheon (dial surround or trim)
with a pointer in it. The numbered
dial itself is made of translucent
plastic material similar to thick
celluloid and will probably be
backlit by a single lamp.
Numbered dials were superseded by dials with the stations marked
in their appropriate positions. The
tuned station was indicated by a
rotating or straightline dial pointer.
These early glass dials were rather
plain but that was soon to change.
Later glass dials made use of colour and were much more attractive
than earlier dials. The stations and
other markings were placed onto
the glass with a multi-coloured
transfer so it's important to treat
the glass with great care when
cleaning it.
During the late 1940s and early
1950s, the glass dials were replaced with plastic dials. These were
very similar to the glass dials except for the use of acrylic sheet instead of glass. Unfortunately,
acrylic sheet is inclined to craze
and crack after 30 years or so and
a radio of this type frequently
shows its age for this reason.
By far the most appealing dials
are those of glass. Provided they
have not been broken, they will look
good for a long time.
Some of the glass dials from the
1940s era were most spectacular.
In some instances, they consisted of
multiple layers of glass with
various parts of the dial printed on
different sections of glass. When all
the layers were assembled, this
technique produced a very pleasing
3-D effect where some markings of
the dial seemed to stand out in front
of other markings.
It is obvious when looking at such
elaborate dials that the dial was
meant to be the focal point of the
set. Restorers should keep this in
Glass dials should be cleaned with care as some station markings can wipe off
quite easily. If the markings are fragile, the best approach is to clean the glass
with a moist cotton bud. It may even be safer not to clean the inside surface if
it is reasonably clean.
This view shows a numbered "peep-hole" dial on a set from the late 1920s.
The dial was made of translucent material and backlit with a single lamp.
mind. If one goes to the trouble of
restoring an old radio, then every
attention should be given to the dial
in order to make it look as near new
as possible.
This means that everything
should be clean and tidy and that
includes the dial glass, its background, the pointer and the dial
surround (or escutcheon).
Cleaning the glass
Cleaning the dial glass can range
from an easy job to a most difficult
one depending on how well the station markings are attached to the
glass. Some dials are so tough they
can be washed under running
water and dried with a towel
without doing damage. But do this
to other dials and all that will be
left is a sheet of plain glass.
The best approach is to test clean
the dial on an outside edge that is
out of view when the dial is installed. Be careful - some dial markings are so fragile they can be
removed with a single wipe.
It is often the older, more
valuable sets that have these super
delicate dials - so don't say you
weren't warned. Believe me, it's a
rotten feeling when you discover
that the station call signs have
relocated themselves onto your
cleaning rag.
Perhaps the best way to clean
,some of these touchy dial glasses is
to gently dodge around the markings with a moist cotton bud. It may
even be safer not to clean the inside
surface if it is reasonably clean.
Many dials are mounted on thin
rubber strips which become hard
and brittle and usually break up
when disturbed. Bicycle tube rubber is an easily obtained replacement. If the glass is remounted on
fresh rubber strips, there is less
likelihood of breaking the glass due
to uneven pressure.
When replacing a dial glass
make sure that it goes back in the
correct position in relation to the
cabinet. Few things look worse than
a crooked or poorly positioned dial.
Dial pointers can always be
brightened up with a touch of paint.
Red, black and white seem to be the
most common colours. Once again,
a simple job such as repainting the
dial pointer will give the dial that ·
new look and make the set more
presentable.
The dial's background is also an
area that can require attention.
This can vary from a simple wipe
with a damp cloth to a dust down
with a fine brush, a coat of paint or
replacing a sheet of coloured
paper. Once more, it is these little
details that make all the difference.
To finish off the job, the escutcheon will need to be cleaned and
polished, whether it be metal or
bakelite. Cleaning with hot soapy
water and a nail brush should be
sufficient in most cases.
A bakelite escutcheon can be
polished by giving it a good rub
down with "Brasso" or some other
fine abrasive metal polish. The
Brasso treatment will restore
bakelite and other plastics to new
again. The fine abrasive action of
the polish removes surface oxidation and brings up a good lustre.
Brasso is also a useful cleaning
and polishing agent for those
moulded cellulose acetate dial
"glasses" that are common on
many old radios. Great care needs
to be taken with these old dial
covers because after 40 years or so
they become very brittle and are
easily cracked or broken if handled
roughly.
Next month's vintage radio topic
will be on IF transformers and
coils.
~
DECEMBER 1988
17
HIFIREVIEW
Harman Kardon PM665Vxi
150 watt stereo amplifier
Harman Kardon is back. Those who remember this
quality brand, originally made in the USA, will be
delighted to learn that Harman Kardon products
are as good as ever and again available in
Australia. To set the ball rolling we review their
top of the line integr·ated amplifier, the PM665Vxi.
By LEO SIMPSON
Harman Kardon refer to their
PM665Vxi amplifier as a high
voltage/ high current design.
Arguably, it is a high current
amplifier, as it is rated to deliver
peak currents to the loudspeakers
of up to ± 80 amps. This enormous
current capability is provided so
that the amplifier can cope with
speakers which have very low impedances when fed with dynamic
signals (ie, music instead of steadystate sinewave signals).
It is also a relatively high power
amplifier, rated to deliver 150
18
SILICON CHIP
watts per channel into 80 or 40
loads. That equal power rating into
80 or 40 loads is interesting
because most amplifiers deliver
quite a lot more power into 40
loads. This is a natural consequence of the fact that a power
amplifier is a close approximation
to a voltage source (ie, it has a very
low output impedance) and therefore delivers more power into lower
impedances.
On the PM665Vxi, Harman Kardon have turned that convention
around by providing two switches
on the back panel, to select the load
impedance, 40 or 80. We did not
have a circuit of the unit at the time
of writing but we deduce that the
switches change the supply voltage
to the output stage: high for 80,
lower for 40.
The reason for doing so becomes
clear after the amplifier has been
running for half an hour or so; it
gets quite hot. Evidently it operates
with a high quiescent current (ie,
the current when no signal is present) as part of the Harman Kardon
philosophy of designing their
amplifiers with a minimum of
negative feedback.
By operating with a high quiescent current the amplifier will effectively be in class-A mode for
most of the time and so will be inherently more linear: hence less
need for negative feedback.
However, because of the relatively high quiescent current the
designers have then sought to
an apparent difference to the
amount of boost and cut available.
In the hands of a knowledgeable
user variable turnovers can be worthwhile but with average listeners
they could be a source of confusion.
For the latter people we'd suggest
they select 200Hz and 2kHz and
leave it at that.
The purists are catered for too,
of course, and the tone controls can
be switched right out of circuit with
the Tone Defeat switch.
Capacitance trimming
The interior of the PM665Vxi is dominated by two large finned heatsinks and
by two large power transformers on the lefthand side. Both the cover and
bottom panels are entirely covered with ventilation slots to dissipate the heat
from the heatsinks.
minimise the increase in power
dissipation caused when the
amplifier is actually driving the
load. To do this, the supply voltage
is reduced when 40 loads are to be
driven.
This also gives a margin of safety
for the output transistors, especially when they are called upon to
deliver the very high currents they
are rated for.
The PM665Vxi is a big beast. It
measures 443mm wide, 134mm
high and 398mm deep, including
knobs, rubber feet and rear projections. It is heavy too, weighing in at
14.2kg.
Harman Kardon styling is strictly
conventional; finished in black,
with fine gold lettering. Along the
lower half of the front panel is a
row of rotary controls while along
the top is a row of tiny pushbuttons
to engage various functions. All the
usual functions are there plus a lot
of others.
In fact, it is probably one of the
most feature-laden integrated
amplifiers presently available.
For example, the tape monitor
switch doubles as a VCR selector so
it switches video signals as well as
the stereo audio signals from hifi or
stereo VCRs. Dubbing between two
VCRs or two tape decks is provided
by the Record Out switch, which is
right next to the Tape Monitor
switch.
Turnover switches
A comparatively rare feature on
integrated amplifiers these days is
the provision of variable turnover
on the bass and treble controls.
"Turnover" refers to the 3dB (ie,
half power) boost or cut frequency
obtained when the tone controls are
set to their maximum or minimum
settings.
On most stereo amplifiers the
bass turnover frequency would be
around 300Hz while the treble
turnover would be around 2kHz.
The PM665Vxi has pushbutton
selectable turnovers at 200Hz and
400Hz for the Bass control and
2kHz and 6kHz for the Treble.
Usually, changing the turnover
frequency will not markedly affect
the maximum amount of boost and
cut at the upper and lower audible
frequencies but it will make quite
An even rarer feature on amplifiers is the provision of capacitance trimming for the moving
magnet cartridge inputs. This is
very worthwhile since the flatness
of frequency response obtainable
from magnetic cartridges can vary
quite markedly, depending on the
load capacitance. To give optimum
flatness in the high frequency
response some cartridges require
200pF of capacitance or less while
others require up to 500pF or more.
Typically, the leads from the
turntable to the amplifier will provide about 100-150pF of capacitance in each channel while the
preamplifier inputs will typically
add another lO0pF or so. By contrast, the "Cap Trim" switch on the
PM665Vxi gives input capacitance
loadings of normal (125pF),
+ l00pF, + 200pF and + 300pF.
This gives a minimum capacitance
of 125pF and a maximum of 425pF,
so if you know the capacitance
recommended by the manufacturers of the cartridge, you can pick
the closest setting.
The Harman Kardon also has a
pair of phono inputs to cater for
moving coil cartridges, as selected
by a small button to the right of the
Volume control.
Some larger integrated amplifiers can be split into separate
preamplifier and power amplifier
stages by pulling out ·a couple of ·
bridging links between two pairs of
RCA sockets on the rear panel. On
the PM665Vxi, the four sockets are
there (labelled Pre-out and Main-in)
but instead of the bridging links
there is a switch on the front panel.
Other small pushbuttons are provided for Loudness, Subsonic and
High Cut filters, Mode (mono or
DECEMBER1988
19
The PM665Vxi has comprehensive facilities and includes a number of RCA sockets with yellow centres to distinguish
them as video inputs and outputs. Two slider switches (top right) are used to select the load impedance (either
40 or 80).
stereo) and Mute. We should note,
at this point, that it is hard to tell
the settings of these buttons at a
glance, especially if the lighting is
dim, which is normally the case in
typical living rooms. This is not
helped by the very small printing
for -the labelling on the front panel.
We believe this is too small for most
people to read easily.
On the rear panel, there is the
usual array of RCA sockets for input and output signals and there
are a number of RCA sockets with
yellow centres to distinguish them
as video inputs and outputs.
The speaker terminals are good,
being those shrouded binding posts
which will take heavy wires. These
are better than the spring-loaded
terminals found on many stereo
amplifiers.
Ventilation
This amplifier is one that should
not be stacked with other equipment because it needs plenty of ventilation. Both its cover and bottom
panels are entirely covered with
ventilation slots to dissipate the
heat from the large internal
heatsinks.
Removing the top cover reveals
more details of the interior which is
dominated by the two large power
transformers on the lefthand side of
the chassis. These make the unit
much heavier on the left and
somewhat difficult to lift, for that
reason.
20
SILICON CHIP
Specifications
Continuous power output
Rated harmonic distortion
Power bandwidth
Output current capability
Frequency response
Signal-to-noise ratio
(with respect to rated power,
A-weighted)
Phono overload (at 1 kHz)
Filters
Dimensions
Weight
Both transformers are wellshielded to cut down on hum
leakage. They are fitted with copper straps and metal sheathing
over the laminations. This is particularly important in an amplifier
which has to handle video signals
as well as low level audio signals.
As far as we can tell without access to a circuit, the power supply
appears to be quite conventional,
employing 16,400µF of capacitance
for both the positive and negative
supply rails. Gleaning information
about the power amplifiers is more
difficult but the output stages appear to use high power Darlington
1 50W into 40 or 80 (both
channels driven)
0 .08% into 80; 0 .1 % into 40
1 OHz to 1 OOkHz
± 80 amps peak
0.2Hz to 150kHz, -3dB
80dB phono {moving magnet)
76dB phono {moving coil)
98dB video/CD
11 OdB main in {power amp only}
220mV RMS {moving magnet);
12mV RMS (moving coil)
6kHz, 6d8/octave {high cut);
15Hz, 6d8/octave (subsonic)
443 x 134 x 398mm
14.2kg
(ie, bipolar not Mosfet) transistors
which have large plastic encapsulations. There are four such transistors in each channel.
Wide bandwidth
Harman Kardon have a policy of
using discrete components throughout their circuits. This is necessary,
apart from anything else, because
this company is noted for designing
its amplifiers with very wide
bandwidth.
This amplifier certainly follows
that philosophy. The frequency
response from the high level inputs
is quoted as 0.2Hz to 150kHz, at
- 3dB points, at a power level of 1
watt.
Similarly, the half-power bandwidth is quoted at lOHz to lOOkHz.
These figures are quite exceptional. We had no trouble in confirming them.
SPECTACULAR
ELEASE
vHa
Performance
Rated power output from the
PM665Vxi is quoted at 150 watts
per channel into 80 or 40, with both
channels driven. Rated harmonic
distortion is less than .08 % for 80
loads and less than 0.1 % for 40
loads.
Our tests easily confirmed the
power output although the typical
distortion figures were somewhat
better than those claimed. We
measured around .02% across the
board.
Actually, a harmonic distortion
figure of .02 % is not particularly
low these days and competitive
amplifiers would measure considerably better. However, Harman
Kardon's figure is to be expected,
as a result of designing the
amplifier with a mm1mum of
negative feedback. Even so, a figure
of .02% is still very respectable.
Rather than go through each performance parameter we can report
that we were able to confirm all the
other specifications listed in the
separate panel. The telling is much
quicker than the doing, of course,
as it takes almost a whole day to
confirm all the specs in a comprehensive integrated amplifier
such as this.
Sound quality
And what about sound quality?
It's every bit as good as you'd expect a top quality amplifier to be.
With its comprehensive control
facilities, bags of power, solid construction and conservative design,
it is sure to give many years of
musical satisfaction.
If you're in the market for a new
stereo amplifier, you should give
the Harman Kardon range a careful
audition.
Recommended retail price for the
Harman Kardon PM665Vxi is
$1995. For further information,
contact the Australian distributors
Convoy International Pty Ltd, 400
Botany Road, Alexandria NSW
2015. Phone (02) 698 7300.
~
NEWSA-100
SPEAKER KIT
Since the introduction of VIFA speaker kits
in Australia in 1985, thousands of speakers
have been built with superb results. VIFA is
now proud to release four new speaker
kits ranging from a mere $399 to $1199 per
pair including cabinets.
Never before have speaker kits been so
popular in Australia than after the heavy
devaluation of the dollar. Similar fully
imported quality loudspeakers are today
typically 2-2½ times more expensive. And
these speakers may very well be using
Danish VIFA drivers anyway, as VIFA
supply more than 50 of the world's most
respected loudspeaker manufacturers
with drivers.
But why the big savings? Because
fully imported speakers suffer from 25%
import duty, 20-30% freight, 30% sales tax
and 28% handling charges (typically). So if
you would rather put your money into better
quality than in other people's pockets, VIFA
speaker kits are the only way to go.
Are they difficult to build? No, the kits
are supplied with all parts needed including
fully built crossovers and pre-cut flatpack
cabinets ready to assemble. No soldering
or carpentry skills are needed, just a
Phillips head screwdriver, some simple
hand tools and a few hours of your leisure
time.
Are they as good as people say? Read
the reviews, listen and compare with any
other speakers twice the price or more.
Need we say anymore?
VIFA for the quality conscious
audiophile.
For full details please contact
Sole Australian Distributor:
SCAN AUDIO Pty. Ltd.
P.O. Box 242, Hawthorn 3122.
Fax (03)4299309
Phone:
4292199 (Melbourne)
(02 5225697 (Sydney)
(0 3577433 (Brisbane)
(09 3224409 (Perth)
Stocked by leading stores throughout Australia
(O!
Polystyrene capacitors
YES
Made here in Australia?
YES
Made Special to Type?
YES
Where From?
Allied Capacitors Australia
Allied Capacitors Australia specialises in custom made good quality, high
stability polystyrene capacitors . Why design circuitry which requires additional
components to achieve a specific capacitance ; we can wind exactly the
capacitance you need to match your design criteria within the ranges of 1OpF to
1 µF and up to 10,000VDC.
Capacitors are manufactured to 0 .25%, 0.5%, 1.0%, 2.0% , 2.5% , 5%, 10%
and 20% and are priced according to tolerance. All capacitors are tested to 2.5
times the rated voltage.
~--wwwwwwwwww ·
Interested?
Call us now on:
(02) 938 4690
OR Cut out and post this coupon to
Post Office Box 7 40
Brookvale, N.S. W. 2100
I Yes,
I am interested in your capacitors.
I Please post me
details of the following values:
. .. I . .. VDC ... I . . . VDC ... I . .. VDC . .. I . . . VDC .
Name
(Please print)
Address
~-------------~-~~~~~~~~~~~J
DECEMBER1988
21
GEL
BATTERY
SURPLUS
BARGAIN
We have purchased a quantity
of Natklnal brand 6 volt Gel
rechargeable batteries. These are
ideal for burglar alarms, or where
any back-up power supply is n99ded.
Connect two in series to give 12 volt.
Two sizes available:
2.4 AMP 6 VOLT Cat. SB-2490
$9.95 5+ $8.95 ea
8 AMP 6 VOLT Cat. SB-2492
$24.95 5+ $22.50 ea
Japanese made
2.4A size: 98.5(H)x66(L)x33(W)m
BA size: 94(H)x151(L)x50(W)mm
Another surplus stock buy. These are a high quality black thermoplastic PCB
terminal strip. As used by the alarm Industry. Available In 4 way and 1O way.
Units are supplied unasserrbled • I.e. you have to screw the screws In.
Normal
Price
10+
100+
4way
$2.50
$1.50
$1 .30
Cat. HM-3204
10 way
$4.95
$2.00
$1.80
$1.50
Cat. HM-3205
BELOW WH,OLESALE PRICE
'
.
4 WAY PCB TERMINAL BLOCK
Limited quantity, surplus purchase. Solder direct to PCB and
connect wires, NORMALLY $1.75 Cat. HM-3174
SPECIAL PRICE $1.00 each
DIGITAL PANEL METER
CATALOGUE
A brand new 18 page Lascar catalogue Is
available from the Australian representative,
Jaycar Electronics. The catalogue features the
latest Surface Mount Technology DPM's from
Lascar • the world's leading DPM manufaclurer.
Panel meters are available in both liquid crystal
and LED-type displays. All DPM's come
complete with snap-on bezels. Full technical
information Is provided for the 50-odd products
described.
Contact Jaycar branches or
Hea d Off.Ice for a free copy Of
the c:atalogue.
--~p-------------1
A JAYCAR/SILICON
CHIP EXCLUSIVE KIT
PLASMA DISCHARGE
DISPLAY
Ref: Silicon Chip August 1988
Jaycar and Silicon Chip
have corrbined to produce
a klw cost but spectacular
plasma discharge display.
The Jaycar kit of this project
includes the rare-earth
chamber, mounting plinth,
EHT transforrrer and
Inverter electronics.
A 2-3 arrp 12v DC power
supply is required.
(A battery charger is ideal).
Call in to one of our stores
forademol
~(l!)(!Dll!l!J.W8'
~
AA Ni Cads
;~::~~
-
$3.50 each
or 4 for $12.50
A.11J]D)II(O) A.lMIIP'
Til)
J.\
TO)
tM J.\ TTIC'J
Don't waste money.
Buy rechargeable
NiCads, 450mA.
Quality brand.
Cat. SB-2452
.I..C)~l.l,ll'~.!.'-J
Completely built, this module measures 63 x
35mm, has a high Input impedance and high
gain. Runs on 9V and requires a 15 ohm load.
Supplied with full specs and data. Made In
England!
Cat.M-02920NL
4f
OLD NI Cad BATTERIES
ARE DANGEROUS
Y $3.95
Bring in your worn-out NiCads in December
and we will dispose of them safely for you.
As a bonus we will give you a 5% trade-in allowance on new onesl
10+ $3.50 each
We have a small quantity of 15 ohms· x 4"
speakers to suit. Otherwise just use two 8 ohm
speakers in series.
Cat. AS-3013
$3.95
DECEMBER ONLY
(Don't forget • all those toys use lots of
battery power!)
Cat. KC-5035
,.
NEW LOW
PRICE $229
SAVE $70
UHF TUNER
Sanyo Model T1087RA
Yet another scoop purchase
A compact high quality tuner that operates
from 526-814MHz (corresponding to channels
28 thru 63). This tuner is designed for
Australian standard reception (AS1053 1973),
and Is offered at a very low price.
Knob not supplied.
Cat. DM-1000
NORMALLY $29.95
SAVE $15.00
THIS IS RARE!
WAS$299
Savings mad
of mass prod
Tonearm cable. Yes, we've finally been able
to locate a small quantity of 4 core tonearm
cable. This cable is twisted together and
total diarreter is approx. 2mm. 1 metre
length.
Cat. WH-3035
$2
tdoor Inl"ra Red Motion Detector
al for both residentiM ~ a comrrerc1a1 apllcatlons. Completely self contained and
asy to Install. Designed to mount directly
standard round junctkln box.
he unit will automatically turn on two
odlights when sorreone walks within the
elector range. Ideal security system to
rotect loved ones and property. Detection
nge is 40 1881 long by 60 1881 wide. Light
ill stay on for a minimum of 1Oseconds u
15 minutes (adjustable). Works only at
ight. Globes not supplied.
at. LA-5t32
NEW'88
NLY $139
12V CAR ANALOGUE
CLOCK MOVEMENT
MASSIVE SCOOP
PURCHASE!
Grab a quartz crystal car clock with a set of
automotive style hands at a price that will
astonish you I Once again our suppliers huge
loss Is your gain I Convert that broken/
unreliable or inaccurate mechanical clock in
your car to space age precision I
Made In West Germany by VDO, the module
measures roughly 45 x 38 x 40 deep. The
compact size virtually ensures that It will fit In
anyspacel
Quantity strictly limltedl
Cat. XC-0108
ONLY
$9.95
"PLASTI-DIP"
Heavy Duty Flexible
Liquid Coating
BACK AGAIN!
White Cone
Midrange
Our most popular midrange. Large sealed
back with extra clear crsip midrange.
110mm, 80 watts RMS power handling,
95dB sensitivity, 10oz magnet, freq . rasp.
31 Hz• 7kHz, resonant freq . 310Hz.
Cat. CM-2080
1986 PRICE eat your heart out Dickll
ONLY $22.5
Plastic Dip Is an air dry liquid
plastic coating that produces
a tough, thick pliable finish.
It Is Ideal for making a pliable
coating for the handles of tools,
etc.
Supplied In a 470ml dipping
can. WIii do dozens of tools.
Cat. NP-1100
RED IN COLOUR
,,.
0 NL Y
$24 .95
NEW'88
;j
,,-.,,;;:"1""'":"=-.:,...,I
,
.
\;/1','P
:.:.;~..:-:~-·
.~~i;;.::,~
__;.-·
Piezo Tweeter
,"l
Polypropolene
Cone Midrange
6 WAY POWER OUTLET
_WITH MAINS FILTER
We've been able to lower our pri,:e on our
Not only Is It a 6 way power board, it incorporates a voltage surge and spike protector and
noise rejection filter network. Supplied with 2
metre cord and mains plug, safety shutters on
each outlet. Illuminated master on/off switcvh
and even a safety circuit breaker.
Cat. MS-4000
high power midrange. Black Poly cone.
Huge 10oz magnet. 5" diameter.
Specifications:
Power handling
100 watts RMS
system
Resonant Freq.
570Hz
Sensitivity 96dB
Freq. Rasp.
570Hz • 7kHz
Cat. CM-2085
At last, an economical priced quallty piezo
tweeter. Another manufacturers surplus stock
purchase by Jaycar. These are in other
catalogues for $18.951
SPECIFICATIONS
• Frequency response 3.5kHz-40kHz
• SPL 94dB/1W at 1 metre
• lntermiitent peak power 100 watts
• Size 78mm square
• Use with or without crossovers
Cat. CT-1905
UNREAL PRICE
9.9
$59.95
PASSIVE INFRA RED
DETECTOR - PRICE
BREAKTHROUGH
It had to happenll
Jaycar was the first to offer pulse count PIR's
and lately we were the first to offer pulse
count for less than $100. We are proud to
announce another first In PIR's.
A QUALITY PIR FOR ONLY $69.95 FULL
PRICE
Sure, you are probably thinking "but what
about the quality and reliability". There's
nothing worse than an alarm system that
false triggers, you know the old story about
the boy who cried won.
We have extensively tested the units and
have no doubt about their quality and
operation ability.
Features & Specifications
• Dual element pyroelectric sensor
• 24 dual element detection zones In three
layers
• Wide angle 90" multi layer coverage
• 12 metre range
• Operation voltage 7.5 • 16V DC
• TaJTl)0r protected
• LED Indication
• Size 65(H) x 84(WJ x 46(D)mm
• Colour beige
• Relay output
• 3 month guarantee
Cat. LA-5017
NLY$69.95
$30 LESS THAN ANY PIR WE
KNOW OF
NOTE: If you require absolute mains
suppression don't forget our Australian made
Squeaky Clean Mains Filters.
SAVE ON ADCOLA
CONE TWEETER
SOLDERING;· The newest ediUon to our speaker range.
~~!!u~~~~ecs
BASE STATION
NORMALLY $159.50 /
SAVE $20
,
DECEMBER PRICE $139.50
Cat. TS-1475
40W IRON • CT6
NORMALLY $49.95
SAVE$5
NOW ONLY $44.95
70mm cone tweeter.
Norn lrrpedance 8 ohms
Max power
75 watts
Freq. Range
3kHz • 18kHz
Sensitivity
91 .5dB
Flux density
7,200 Gauss
Magnet size
45(dia) x 22(dia) x 9mm
Magnet Weight
47.4 grams
Net Weight
170 grams
Cat. CT-2000
WAS $11.95
Another surplus stock purchase.
The quality is first class, the only problem is
the colour. It would have been totally In
vogue In the 1950's or 60's, but It's not really
suited to the loungerooms of the SO's. If you
have speakers In the rumpus room, garage,
boys room etc.. that require cloth then this
cloth Is Ideal'. Oh, we haven't told you about
the colour yeti
'It Is also ideal if you REALLY want to be
MEGA trendy!
SAVE$2
NOW$9.9
Cat. TS-1478
BOW IRON - CT7
NORMALLY $55.00
SAVE$7.50
NOW ONLY $47.50
Cat. TS-1480
-~~-•I STYLE 1 Gold with black strips at about 1
Jaycar Introduces the Easy way to
Buy
Greencaps
Don't aver run short of that greencap again. 5 easy to buy, low cost packs which
represents a considerable saving over individual prices.
Each pack contains 1O of each value and packs cover the complete range from
0.001uFto0.1uF.
Values: (10of each) 0.001, 0.0012,0.0015, 0.0018, 0.0022
A GREAT
$6.95
TOTAL 50 pieces Cat. RG-5000
Values: (10 of each) 0.0027, 0.0033, o.0039, 0.0047, 0.0056
TOTAL 50 pieces Cat. RG- 5001
$6.95
Values: (10 of each) 0.0068, 0.0082, 0.01, 0.012, 0.015
$6.95
TOTAL 50 pieces Cat. RG-5002
Values: (10 of each) 0.018, 0.022. 0.021, 0.033, o.039
$6.95
TOTAL 50 pieces Cat. RG-5003
Values: (10 of each) 0.047, 0.056, 0.068, 0.082, 0.1
TOTAL 50 pieces Cat. RG-5004
"CRIME STORY"
SPEAKER CLOTH SALE
$9.95
WA y TO
NEVER BE
OUT OF THAT
ODD
GREENCAP
AND KSEATVEATA
SAME
TIME
%i
1/2"1ntervals.Slze5'x1mt
Cat. CF-2756
$3 • 95 SAVE $1 O
STYLE 2 Gold with gold reflective pieces
through It. Size 3' x 1mt.
Cat.CF-2757
$2.95 SAVE $7
STYLE 3 It's a bit more down to earth. It's
brown with red, black and green fleck. Size 3'
X 1ml.
Cat. CF-2758
$3.95 SAVE $6
132 pages of electronic goodl86. tt you doni
have our catalogue or nyoU've lost It call In to
any of our showrooms for a free copy. (And a
lollie n you have to wait). OR send a large
SAE to PO Box 185 Concord 2137 and we'll
post you one.
0.1 MONOLITHIC
CAP SALE
We have available a pack of 0.1 monolithic
capacitors with short leads at a very special
price. The only catch is that they have cut
leads ready for machine placing In PC
boards. The leads are about 1.5mm long •
just long enough to go through a circuit
board.
ONLY $7.95 for 100
NORMALLY $16.50 per 100
00"' -
GOVERNMENT INSTRlJ!\ffNTALl"flES,
SCHOOLS, PlJIIUC COMPANIES
IF YOU WISH TO PURCHASE l'RO'.\I t:s,
SIMPLY SEND US YOUR OFFICIAi ,
ORDER AND WE \\'ILL <;IVE YOli A
COMPl,EMENTARY 30 DAY ACCOl :NT.
CLOCK MOVEMENTS WITH BUILT-IN
MELODY MODULE
No more messy, separate modules. All in
the one easy to mount housing.
TWO MODULES are available. Both
chime the hour after playing their tune.
XC-0106 plays Westminster Chimes
each hour then gongs the hour (I.e. 7pm
- 7 gongs).
XC0107 plays a different melody each
hour then gongs the hour.
Both units are supplied with:
• Clock movement
• Speaker and battery holder
• Hook to hang up
• 3 sets of hands
Cat. XC-0106 Westminster chimes/clock movement
Cat. XC-010712 melodies/clock movement
SAVE$12.95overseparateclockmovementandchimes
SOLAR PANELS
2Models
6 volts <at> 240m.A
12 volts <at> 120m.A
Each panel measures 327(L) x 165(W) x
18mmthick.
Cat. ZM-9008
LOUO!,,J1.AKJJ\ l~C"ll)\"\1"f"
DISICN ANO OON~TkUCT10N
-
$79
Cat. ZM-9009
$79
Solar Battery
Charger
ONL V 18.95 ea
Loudspeaker P.A. Bin Enclosure
Designs Book
-
12 volt panel<at> 120mA
6 volt panel <at> 240mA
Fane Acoustics UK, makers of speakers for the
likes of Pink Floyd, David Bowie, Genesis,
Iron Maiden etc. have produced an absolutely
fantastic book on P.A. bin designs. The book
begins with construction info in general, I.e.
what materials to use, how to join timber,
how to brace the cabinets, sealing, lining,
wiring, crossovers, impedance matching, etc.
The second section includes 22 separate
detailed designs for: reflex cabinets,
horns, wedge monitors, folded horns, w bins etc.
Designs accommodate 1O",
12", 15" and 18" speaker components.
m•
jjM,•-.
The solar panel In the lid will charge up to 4
x M N!Cads In a fairly short time. It is Ideal
for yachts, carrpers or anywhere where
240V Is not available.
Cat. MB-3502
Size: 65(W) x 30(H) x 95(D)mm
WAS$17.95
0.45 VOLT SOLAR
CELL MODULES
SOLAR PLANT
TURNTABLE
No more lopsided plants. WIii handle up to
15 kg of weight. Also ideal for store
windowdisplays.
Cat. YX-2503
$
_
17 95
$14.95
l
Cat. BF-4150
Brand New 240V 50Hz Synchronous Motors
We have made a SCOOP PURCHASE of
Double Pole Squirrel Cage motors with
I 8
rubber shock mounting plate (which can be
removed if necessary). The motor is supplied
with an on/off switch (also removable) and
features a 4mm diameter hard steel drive
shaft, 21 mm long (with mounting plate removed).
These motors are ideal for fans or when
reduced , in applications requiring a fractional
HP drive,
Cat. YM-2708
- •
NOW $14.95
Connect in series or parallel. Two sizes.
0.45V
0.45V
75x45x6mm
96x65x6mm
Cat. ZM-9005
Cat. ZM-9006
$3.95
10+ $3.75
-
$6.50
10+ $6.20
Dear Customer
There are times when due to
circumstances beyond our control
some advertised products may
not be in stock when our ads
appear. We suggest you phone to
check availability.
•
.
SOLAR, EDUCATION KIT
WAS $10
NOW ONLY $5
Our solar education kit is designed to let you build your
own solar models. This kit comes complete with :
• Solar cell module
• Solar energy booklet explaining
the whys and hows of solar energy
• Small DC motor
• Screws and nuts
• Wire with motor clips
• Coloured spinner discs
• Paper aeroplane and bird models
• Plastic turntables with 4 sizes, 5/8", Cat. KJ-6690
1', 1 1/2" and 2"
• Plastic fan-spinner
~
~
FOSTER DOME TWEETER - BACK IN STOCK!
The D025N25 is a brilliant tweeter. It's probably the cleanest sounding tweeter we sell. It
handles enormous amounts of power and has a very smooth response,
Power Handling
150 watts RMS system
Freq. Response
3kHx-30kHz
Resonant Freq.
1,200Hz
Impedance
8 ohms
SPL
91d8/1 metre
Flux Density
13,500 Gauss
Weight
610 grams
Cat. CT-2018
ONLY $9.95
SOLAR CAR BATTERY BOOSTER
Keeps your battery charged in your car when you are not using it.
Cat. MB-3503
$29.95
$36.50
12" GUITAR
SPEAKER
Finally available, our updated guitar speaker
with extended frequency response. Especially
suited for not only bass guitar but rythm and
lead as well.
Resonant Freq.
60Hz (was 80Hz)
Impedance
8 ohms
Freq. Response
80Hz - 5kHz
Power Handling
100 watts RMS
Magnet Weight
40oz
Net Weight
·, 3610 grams
Sensitivity
\ 102dB
But the best news is the price· NO INCREASE
Cat. CG-2380
DISCOLITE KIT
Ref: Silicon Chip July 1988
Build your own light show
Cat. KC-5032
"EASY ETCH"
Engraver
$159.5Q
"
'
~
'
_,
!¥: r:·-:~-. . ~
" "'
Features
• Pulse count
• 48 beams
• Sliding PCB
• Hallway lens optional
(Cat. LA-5020 $3.95)
WAS $119
CARLINGFORD STORE
HAS MOVED TO
PARRAMATTA AT355
CHURCH STREET
(Cnr Victoria Avenue)
SAVE $20
NOW
$99
- at last a low cost engraver I
Ideal for permanently marking your valuables
with owner identttication. As ideal for that everlasting message on gifts and trophies.
Features: • Supplied with hardened steel
engraving kit• will engrave virtually any surface
• rotary motion of engraving kit eliminates
vibrations • Works at safe 12V (adaptor
supplied) • Diamond engraving bit available
(Cat. TH-1908 $23,95)
. (Cat.
TH-1912 $10.95)
Cat. TH-1920
JAYCAR-Nol
FOR KITS
Protector Car Alarm
Ref: Silicon Chip Feb 1988
About every feature you could ever want In a
car alarm. See our 1988 catalogue for full
details. Extras not included in kit: Back-up
battery Cat. SB-2490 $22.50 ; Piezo siren Cat.
LA-5255 $17.95; 12 volt siren Cat. LA-5700
$26.50.
Cat. KC-5021
$79.50
Remote Control (Full kit)
Ref: Silicon Chip March 1988
Full form version. Kit includes all compcnents
except box for receiver, piezo siren and piezo
transducer and battery for transmitter. These
items are available separately: Transducer Cat.
AB-3440 $2.75; Piezo Cat. LA-5255 $17.95;
Battery (pkt 2) Cat. SB-2420 $3. 75
Cat. KC-5034
JAYCAR BRAND
NEW MINI TOGGLE
SWITCHES
Economy
Soldering Iron
Quallty mini switches with black plattened
actuator. Rated at 6A 125V, available In a
single and double pole styles.
SPDT
Cat. ST-0546
$3.25 ea
DPDT
25 watt general purpose iron. Ideal for
beginners. Generous mains power cord.
Supplied on attractive card with soldering
Instructions on the back.
Cat. TS-1450
10+ $3.00 ea
Cat. ST-0547
ONLY $16.95
$3.75 ea 10+$3.S0ea
ULTRA MINI TOGGLE
SWITCHES
Conical spare tip Cat. TS-1453 $4.95
24 HOUR: Switch an appllance"ON"
and "OFF" up to 24 times In any 24 hoursl
Uses simple analogue dial with program pins
(8 pins supplied which means that extra pins
are required for more than 8 operations/
day). It Is VERY easy to set and operate - as
opposed to programmable digital types I It
also has a manual override that does not
affect original program setting.
12 month warranty.
Cat. XW-0400
$23.95
Ultra small size. Body only 8mm x 9mm (DP
version) and 8mm x 5mm (SP version)
Rated at 3A 125V.
SPDT
Cat. ST-0540
$2.20 ea 10+ $2.00 ea
DPDT
Plug-In TIME
SWITCHES
Metal Stand to suit Jaycar Soldering lorn
Sturdy metal base with sprung stand and
heat resistant ferrule holder.
Cat. TS-1500
Cat. ST-0542
$2.60 ea 10+ $2.40 ea
$10.95
$79.50
Tip cleaning sponge to suit Cat. TS-1552 95e
(Compare that price with the Weller sponge
7 DAY: Can switch "ON" and "OFF" up to
42 times a week al two hour intervals (16
4
--c~t~~~;h~:~~~~~~~:~ ~ ~1 ~ u~ o~:w~ev~- '-: ;r~:·
"'I
Wiioiiri:ks:'.a_n_d
POL YSWITCHES
Low cost reliable speaker protection. Refer
articles In Electronics Australia July '86.
RN3410 is suitable for protection of
tweeters In systems up to 100 watts. It's
rated at 50 volt and 0.5 arrp. Nominal
resistance Is 0.4 Ohms
Cat. RN-3410 (R.D.E. 050)
$6.95 ea 1O+ $6.65 ea
12V ILLUMINATED
PUSH BUTTON
Jaycar 12V 30W
Soldering Iron
Economy push on/push off with large RED
(20x20mm) actuator with a chrome surround.
Perteet for fake car burglar alarms. Rated 12V
1O arrp 3 pole.
Cat. SP-0745
Ideal marine use. Has car cigarette lighter
plug for convenience. Extra long cord.
Cat. TS-1470
ONLY $6.95
ONLY $11.50
•---------------t
Motorised Siren still the ultimate
noise maker
RN3415 will protecl midrange and woofer
upto 100watts. Rated at SO volt and 1.16
amps. Nominal resistance is 0.12 Ohms.
Cat. RN-3415 (R.D.E. 115)
When your car alarm goes off you want
EVERYONE to know about ill Many car alarms
these days make the same 'electronic' noise
that is Increasingly being Ignored. This
motorised siren makes a racket like the old
police cars of the 60's & 70's. You would have
heard the noise when the air-raid sirens came
on In old WWII movies. EVERYBODY takes
notice!
Grab one now at the never-to-be-repeated price
of only $25.
Cat. LA-5280 NORMALLY ABOUT $70
$6.95 ea 1O+ $6.65 ea
RN3418 Is rated at 50 volt at 2.45 amps.
Nominal resistance is 0.039 Ohms. As used
in 100 watt amp.module Cat. KC-5019 from
Silicon Chip December 1987.
$8~95e~D10:A$8.25 ea
1
NEW LOWER
PRICES
ONLY $25
SMOKELESS
ASHTRAY
In this day and age,
cigarette smoking is
becoming socially unacceptable.
This product will help the poor old smoker by
removing all smoke from a cigarette sitting in
the ashtray.
It works like thls:Switch the unit on, and It will just sit there in
the off mode. When you "light up" simply tap
the ashtray and it turns on and rusn for 10
minutes before going back to the standby
mode. The unit has a silent motor which draws
the smoke insidend through activated charcoal
layers to purffy the air. Operates on 2-C size
batteries or a 3V DC power source.
The ashtray section (where the cigarette sits)
is made from Melamine and just lifts out to
empty and clean.
Stock Is expected early In December In time
for Christmas.
Size: 125mm x 125mm x 75mm.
oNXLv:,s14.ss
y
$229
STUDIO 200 HI FI PREAMP
Ref: Silicon Chip June/July 1988. Excellent quality at a modest price
Cat. KC-5033
gr
Ott; 1
_ M ~-· ff
HEAD OFFICE
21 37
MAIL ORDERS
POST & PACKIN
10
5
8
•_[_::_i_i~_1l_~_1_1_:'_::__;_d;_!_}_:_:_!1______~_t_R~-~-1~_~-~s-:~_~_r_i:.:_!_!
. _:_:B___, ....~ER_s_1oo_l_i_H_I_J_oi_o______
■
s
VISA
MAIL ORDER VIA YOUR
ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50
SYDNEY - CITY 117YorkSt. (02) 2671614-
GORE HILL
188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 - 5.30 Sat 9 - 4pm
PARRAMATTA
BURANDAQLD
144 Lo9an Rd (07) 393 0777 Mon-Fn 9 - 5.30 fhurs 8.30 - Sat 9 -12
Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 -12
355 Crorch SI (Cnr. Victoria Rd) (02) 683 33n
Mon-Fri 9 • 5.30 Thurs 8.30 pm - Sat 9 - 2pm
115 Parramatta Rd (02) 745 30n Mon-Fri 8.30 - 5.30 - Sat 8.30 -12
MELBOURNE-CITY Shop 2, 45 A'Beckett St City (03) 663 2030
121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 -12
SPRINGVALE VIC
Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12
887-889 Springvale Road Mulgrave (03) 547 1022
Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2·
120W public
address amplifier
Today's public address amplifiers are a real
challenge to the designer. They need to combine
very high sensitivity for low impedance
microphones, mixing for several inputs, tone
controls and high power output. The high power
design presented here is our response to that
challenge.
By LEO SIMPSON & BOB FLYNN
We have had quite a number of
requests for an amplifier design for
public address applications. Our
first step in meeting those requests
was to design the rugged power
amp module presented in the
November 1988 issue. In this issue,
we present the microphone preamplifier and mixer stages and
show how to assemble them onto a
printed circuit board.
Two low impedance microphone
inputs are provided and they can be
26
SILICON CHIP
connected as balanced inputs via
3-pin XLR sockets or as unbalanced
inputs via 6.5mm jack sockets. In
addition, there are two stereo line
inputs which means that any program source such as a CD player,
cassette deck or FM tuner may be
connected.
Mixing of these four sources (ie,
two microphones and two stereo
line sources) is provided via four
knobs on the front panel. The other
front panel controls are bass and
treble controls and the master
volume control.
With 120 watts RMS power output, this public address amplifier
will be suitable for a wide range of
installations. It could be permanently set up in buildings such as
halls or churches or used in temporary installations where AC
mains power is available.
Performance
Traditionally, public address
amplifiers have not had low noise,
low distortion and a very flat frequency response. They have tended
to be very utilitarian affairs with
more of an emphasis on reliability
than on good sound quality.
We have taken a conservative
approach to the design of this
amplifier, to ensure stability and to
prevent RF breakthrough. Even so,
the overall performance is rather
better than from run-of-the-mill PA
amps.
+20
~
+10
TREBLE
BOOST
BASS
BOOST
~I'-- ...
/
V
'
.....
,/
.,,v
-20
20
..........
/""
"'-....
~
,/
/
,..... ....
-10
,-
I..--'
.........
V
/
--
/
......
_.,,/
---
Fl ~T
-............
'
/
r--.....
'
....,
...
TREBLE
CUT
BASS
CUT
Fig.I: this diagram .shows
the frequency response
of the amplifier with
tone controls flat and the
effect of each control
when at the maximum or
minimum setting. Note
that there is a small
amount of interaction
between the controls at
mid frequencies.
~
./
I
100
I
I
HERTZ
Part of the reason for this is the
excellent performance from the two
toroidal transformers, one for the
power supply and one for the 1OOV
line output. Not only do both
transformers have low external
radiation but the line transformer
is exceptionally good for its flat frequency response and clean output
waveform.
If we'd had to depend on conventional transformers to obtain the
same performance, the amplifier
would have been a great deal
heavier and probably bulkier too.
All the performance details are
summarised in the accompanying
specification panel.
Preamp and mixer circuitry
Now have a look at the complete
circuit of the PA amplifier as shown
in Fig.1. For each of the balanced
microphone inputs we have used a
low noise LM833 dual op amp. This
is shown in the top lefthand corner
of the circuit. The LM833 dual op
amp is depicted as IC1a and IC1b
which are connected together as a
balanced input stage.
1 % metal film resistors are
specified in the balanced input
stages, firstly to ensure low noise
and secondly to ensure good "common mode" rejection. Common
mode signals are those extraneous
signals which balanced inputs are
intended to reject; eg, hum, mains
hash and other unwanted interfering signals.
500
1k
10k
5k
20k
Specifications
Power Output (RMS)
125 watts into 4 ohms; 90 watts into
80; 1 20 watts into 1 OOV AC line
Frequency Response
30Hz to 30kHz (-3dB) with line output
transformer (all inputs)
Input Sensitivity
340mV (Aux 1 , Aux 2)
0 .5mV for balanced microphones
0.5mV for unbalanced microphones
Input Impedance
50k0 for line inputs (Aux 1, Aux 2)
6000 for balanced microphones
3000 for unbalanced microphones
Harmonic Distortion
(0.3% from 20Hz to 20kHz
Signal-to-Noise Ratio
- 56dB unweighted for microphones
- 72dB unweighted for line inputs
Stability
Unconditional
The balanced outputs at pins 1
and 7 of IC1 are fed to IC2, an
LF351 single op amp, to provide an
unbalanced output at pin 6. This is
coupled via a 2.2µ,F bipolar electrolytic capacitor to the Mic 1 gain
control potentiometer, VR3.
For unbalanced microphones, a
6.5mm socket with integral switch
is used. This grounds the pin 3 input
of IC1a, effectively converting the
circuit to an unbalanced stage with
only IC1b functioning.
IC4, another LM833 dual op amp,
and IC5 provide the balanced/unbalanced input stages for the second microphone input channel. Its
output is coupled to the Mic 2 gain
control potentiometer, VR5.
The two stereo program sources,
labelled Aux 1 and Aux 2 on the circuit diagram, are fed into a 4-way
RCA phono socket. Both channels of
each stereo source are mixed via
1k0 resistors to provide a mono
signal which is then fed to the
respective volume controls, VR6
and VR7.
The signals from the wipers of
VR6 and VR7 are then coupled via
0.12µ,F capacitors and 56k0
resistors to the mixer stage formed
by IC1a, which is one half of
another LM833 dual low noise op
DECEMBER 1988
27
:I:
~
~
n
~
O
~
I
i
,..
.0056
-
.,.
~
I
•
-II
220k
5.6pf
Lf351
IC5
MIC 2 CIRCUlTRY AS ABOVE
-15V
I~
1
.,.
l
-15V
•
2.2
BP
BP
2.2
I
':"
MIC 2 GAINJ'":.~~ ~
VR5
~ttf
5k LOG
I
__Jill __
">-,.-,,.,,, _
*1%
.0015
I
•........
...____________3.9k
IC4
LM833
1eon
.0015
~~
~
AUX 2
■ .-.-;; I
GAiii ,~ ........,,..,..
VR7 '
50k LOG
1k
R ~
~1k
Ry.,.
~1k
Ly
AUX 1 INPUT
I
SINGLE ENDED 4
301!">
*
Jo';n
BA~ANCED
MIC 1 INPUT
V---2
.
39k
3%
~
E-
N-
240VAC
CASE
-;J,,
!
L_:
r----:
04
BC556
1.4V 3.9k;
~
I
[__:
45.5V 22k:
r---.
2.2k
~
8
ru
120W PA AMPLIFIER
I
~~
~h~
= -r~
~
!
-.J
3.9ki2.4V
:.J
seoni-:Lv
07
06
:::r
!
-51V
+51V
r----Wh
.,.
0.22I
!
16VW
22
22
16VW
J)UT
0.22!
SA
0.1
0.1
B
0.22+
0.1
51V
G
0
ECB
0.1
0.1
INmUT
GNO
~
16VW
22
16VW
22
IN
0
-15V
GND
+15V
OUT
ffi
GND
5
S
m/
VIEWED FROM BELOW
ELJc
0.22+
011
1N5404
010
1N5404\·
~ G\,JtJl.. 2s~~34
5A
+51V
◄ Fig.2: the circuit features two
microphone inputs (either balanced
or unbalanced) and two auxiliary
inputs. These signals are mixed in IC3
and fed to a power amplifier stage
(Ql-Q11) which drives a 100V line
transformer.
amp, IC6a. The gain of this stage,
for each of the two inputs, is set by
the ratio of the 56k0 mixing
resistors to the 220k0 feedback
resistor, from pin 1 to pin 2. This
gives a gain of 220/56 or approximately 4 times.
Tone controls
The output of the line source mixer is then fed via a 2.2k0 resistor to
a feedback tone control stage built
around IC6b. This is a conventional
feedback tone control stage which
works as follows. First, assume that
bass and treble controls VRB and
VR9 are electrically centred. This
means that the gain for all signals is
exactly unity; ie, flat across the
whole audible spectrum.
For the treble control, the two
.0015µF capacitors in series with
each side of VR9 pass only high frequencies so that bass signals are
not affected by the setting of the
control. Similarly, for the bass control, the .022µF capacitor in
parallel with VRB bypasses the high
frequencies so that they are not affected by operation of the control.
So when the bass control is
rotated clockwise, its wiper moves
towards the input signal, which
means that the feedback resistance
path from pin 7 to pin 6 of IC6b is
increased. This increases the gain
at low frequencies and therefore
boosts the bass. The same principle
applies with the treble control.
Note that signals from the two
microphones are not passed
through the tone control stage. This
is normal practice in most public
address amplifiers.
Fig.2 shows the frequency
response of the amplifier and the
response of the tone controls.
Main mixer
Following the tone controls, the
signal passes to the main mixer
stage, IC3, via a 39k0 resistor.
Signals to the mixer from the two
microphone stages are fed via
2.2k0 resistors.
Signals from the tone controls
pass through IC3 with a gain of unity (ie, no gain) whereas those from
the microphone stages pass through
with a gain of 39kn/2.2k0 or approximately 18 times.
Signals from op amp IC3 then
pass directly to the master volume
control, VR4. This then feeds the
power amplifier via a 0.47 µF
capacitor.
As an optional feature we have
included a mute facility on the mixer board. This can be used with
microphones which have a press-totalk switch. When the mute switch
S1 is closed, it kills the signal from
the program source (Aux 1 or 2)
and gives the microphone signal a
clean background. It works as
follows .
Normally, Q12 is biased off by
the 10k0 resistor connected from
its base to the + 15V supply.
Because Q12 is not conducting, Q13
has no base current and so its collector emitter impedance is high.
When Sl is closed, Q12 conducts
and supplies base current to Q13 .
Q13 then acts as an audio switch
to kill the signal at the input to the
tone control stage. Note that
because of the 47µF bipolar
capacitor in series with the collector, no DC current flows through
Q13. This is an unusual use for a
transistor but it works quite
effectively.
In our prototype PA amplifier we
- have shown transistors Q12 and
Q13 on the board but we have not
provided a connection to the
microphone inputs.
The power amplifier module is
identical to that described in last
month's issue, so we will not
describe the circuit here.
Power supply
The power supply is based on
that featured in last month's issue
but includes the additional components needed to provide balanced ± 15V rails for the preamp and
mixer stages. These additional components are mounted on·one end of
the preamp board which is shown
as Fig.3.
The AC mains supply is passed
via a 2-amp fuse and then double
pole switch S2 to the primary of the
300VA toroidal power transformer
:;:;:~""'
_;~~~ !:.2;!-'""·
~~:-~
r~22M
~
22µ,F
0
L _ _:~~~=-+--------'
Fig.3: here's how to wire up the
preamp/mixer board. Use PC stakes at
all external wiring points and make
sure you don't confuse the two
3-terminal regulators. Note the three
wire links.
(Altronics Cat. M-3092). Its two
secondary windings drive a 35-amp
bridge rectifier and two B000µF
63VW electrolytic capacitors to
provide balanced ± 51 V supply
rails for the power amplifier board.
These high voltage rails also feed
via 6800 5W wirewound resistors
DECEMBER 1988
29
·~
The close-up view shows the completed preamp/mixer board installed in the chassis. Notice how the two 6800 5W
resistors at the bottom lefthand corner of the board are mounted end on. The metal tabs of the two 3-terminal
regulators go towards the front panel.
to 33V 1W zener diodes. The zeners
act as pre-regulators for the
3-terminal regulators. By selecting
33V zeners with a tolerance of
± 5%, the regulators are protected
against excessive input voltage; the
7815 positive regulator can withstand a maximum of + 35V while
the negative 7915 regulator can
withstand - 40V.
The ± 15V supply rails from the
3-terminal regulators are further
bypassed by a number of 22µF and
O.lµF capacitors to lower the output impedance and filter out any
hash.
The 33V 1W zeners should be
5% tolerance. The two 6800 5W
wirewound resistors are stood on
end, as shown in the photos.
You will need 40 PC pins for all
the connections from the mixer
board to external components such
as the potentiometers.
When the mixer board is
assembled put it aside and start
work on the amplifier module.
The wiring layout of Mosfet
amplifiers is very critical so the
printed board is a crucial feature of
the design. The printed board
measures 163 x 95mm and is coded
SC 01111881.
As published last month, the
board was mounted on a large
diecast heatsink with integral
rightangle bracket. As used in this
PA amplifier it is mounted on one of
the side heatsinks with. a heavy
gauge aluminium angle bracket.
Assembly of · the board is a
straightforward matter but it
should not be hurried. First, you
should closely inspect the board to
see if there are any shorted tracks
or open circuits in the copper pat-
Construction
As noted above, we built the new
public address amplifier into a rack
mounting case. The one used in our
prototype amplifier was supplied
by Altronics Distributors Pty Ltd
who also are the source for the
toroidal power transformer and
line output transformer.
The mixer and preamplifier circuitry is mounted on a printed circuit board measuring 259 x 78mm
and coded SCO 1112881.
Assembly of the mixer board is
quite straightforward (see Fig.3).
Take care to ensure that the integrated circuits, electrolytic capacitors and diodes are all installed
the right way around. Watch the
regulators too and don't swap them
around inadvertently, otherwise
they'll blow.
30
SILICON CHIP
The two input transistors (Ql & Q2) on the power amplifier PCB must be glued
together using super-glue. This is done is minimise temperature drift of the DC
output voltage.
Fig.4: here's how to install the parts on the power amplifier board. Keep the component leads short
and make sure that the Mosfet output transistors (Q8-Q11) are electrically isolated from the heatsink.
The 2200 resistors shown dotted are mounted on the copper side of the board.
-SCREWS
Two layers of wire are wound on so
that the start is at one side and the
finish is at the other side of the bobbin. Bend the start and finish leads
at 90° and scrape off the enamel
coating before soldering the choke
to the board.
Heatsink assembly
0
0
PCB
I
-1
SHAKE-PROOF
· - - • - W ASHERS
~•
~-NUTS
Fig.5: this diagram shows how the Mosfet output transistors
are mounted on the heatsink. Use your multimeter to check
for shorts between the case and heatsink after each
transistor is mounted. The nuts should be soldered to the PC
pattern after assembly to ensure reliable contact.
tern. These should be fixed before
proceeding further. The PCB component diagram is shown in Fig.4.
Fit the small components first,
such as the resistors and diodes.
Make sure that you don't confuse
the small diodes (1N914s) with the
11 V zeners. The fuse clips, trimpots
and small transistors can be
mounted next.
Qt and QZ should be mounted so
that their flat faces · are touching.
When you have soldered them in
place, put a drop of super-glue between them and squeeze them
together.
The 4.3µH choke at the output of
the amplifier is wound with 19.5
turns of 0.8mm enamelled copper
wire on an 11mm plastic bobbin.
The four Mosfet power transistors are mounted on a 4mm thick
extruded aluminium heatsink
bracket but with their leads passing
through and soldered to the printed
board. The assembly is as shown in
Fig.5.
We used 5mm fibreglass tubing
for the insulating bushes. Smear all
the mounting surfaces of the
Mosfets and the heatsink with heatsink compound before assembly.
The transistors are fastened to
the heatsink bracket using 12mm
6BA screws and nuts. Solder the
nuts to the PCB pattern after
assembly to ensure reliable contact. Alternatively, if the nuts are
nickel plated or stainless steel, use
lockwashers.
As each transistor is mounted,
use your multimeter (set to a low
"ohms" range) to check that its
case is insulated from the heatsink.
After the nuts have been tightened and soldered, the gate and
DECEMBER1988
31
PARTS LIST
Power Amplifier Module
1 PCB, code SC01111881,
95 x 163mm
1 aluminium angle bracket,
4mm thick, 32mm wide,
170mm long, drilled for four
T0-3 power transistors and
to match the PC board
4 3AG fuseclips
2 5A 3AG fuses
6 PC pins
1 plastic coil bobbin, 12mm
diameter x 11 mm long;
Siemens B65672-B-T1 or
equivalent (or 4.3µH aircored choke; see text)
4 T0-3 transistor mounting kits
Semiconductors
2 2SK 1 34 Mosfet transistors
2 2SJ49 Mosfet transistors
4 BC556 PNP silicon
transistors
1 BC548 NPN silicon transistor
1 BF4 70 PNP silicon transistor
1 BF469 NPN silicon transistor
9 1 N4148, 1 N914 small signal
diodes
2 11V 400mW or 1W zener
diodes
2 1 N5404 3A silicon diodes
Capacitors
1 22µF 16VW PC electroyltic
1 0.47µF 16VW PC
electrolytic
1 0.27µF metallised polyester
(greencap)
4 0.22µ,F metallised polyester
(greencap)
1 .001 µF metallised polyester
1 39pF ceramic
Resistors (0.25W, 5%)
1 x 27k0, 3 X 22k0, 2 x 18k0
0.5W, 2 X 3.9k0, 2 X 2.2k0, 1 x
1kQ, 1 X 6800, 4 X 2200, 2 X
680, 3 x 120 1 W, 1 x 5000 trimAOt (Bourns Cermet horizontal
source leads of the Mosfets can be
soldered to the PCB pattern. The
four gate resistors are then
soldered in place, on the copper
pattern side of the PC board.
Now closely inspect all your work
for correct assembly and soldering.
Make sure there are no blobs of
solder bridging out tracks. As a
32
SILICON CHIP
mount, 0.2 x 0.4-inch), 1 x 2000
trimpot (Bourns Cermet horizontal mount)
1 4 7 µ,F bipolar electrolytic
capacitor
4 1 on 0.25W resistors
Mixer Board
Hardware & Power
Supply
1 PCB, code SC01112881,
259 x 78mm
40 PC pins
Semiconductors
3 LM833 dual low noise op
amps
3 LF351, TL071 Fet-input op
amps
2 33V 5% 1 W zener diodes
1 7815 15V positive regulator
1 7915 15V negative regulator
Capacitors
2 220µF 35VW PC
electrolytics
4 22µF 16VW PC electrolytics
2 2 .2µF bipolar PC
electrolytics
2 0 .12µF metallised polyester
(greencap)
6 0. 1µF ceramics or
green caps
1 .022µF greencap
4 .0056µF greencap
6 .0015µF greencap
1 33pF ceramic
1 5.6pF ceramic
Resistors (0.25W, 5%)
1 x 220k0, 2 x 56k0, 2 X 39k0,
2 X 27k0, 1 x 18k0, 2 X 12k0, 4
X 6.8k0 1 %, 4 X 3.9k0 1 %, 4 X
2.2k0 1 %, 3 x 2.2k0, 4 x 1 kO, 2
x 6800 5W wirewound, 4 x
3010 1 % , 2 X 1 800 1 %
Potentiometers
2 1OOkO linear potentiometers
2 50k0 log potentiometers
1 1 OkO log potentiometer
2 5k0 log potentiometers
Optional mute facility
1 BC558 PNP transistor
1 BC548 NPN transistor
final check on your work, connect
your multimeter (set to a low
"ohms" range) and test for shorts
between the supply rails and the OV
rail. There is a trap here - flyback
diodes DlO and Dl 1 will show a low
resistance for one connection of the
multimeter and a high resistance
for the reverse connection.
1 3-unit rack mounting case
with extruded aluminium side
panels, Altronics Cat. H-0418
1 300VA power transformer,
70V centre-tapped, Altronics
Cat. M-3092
1 160VA 1 OOV line
transformer, Altronics Cat.
M-1124
2 3-pin XLR chassis mounting
sockets
2 6.5mm mono jack sockets,
chassis insulated, with
changeover switch
1 4-way RCA phone socket
panel
1 red binding post terminal
1 black binding post terminal
1 3-core mains power flex with
moulded 3-pin plug
1 cordgrip grommet to suit
power flex
1 4-way insulated barrier
terminal block
2 solder lugs
1 35-amp bridge rectifier,
Altronics Cat. FB-3504
2 8000µ,F 63VW electrolytic
capacitors
1 3AG 2A fuse and chassis
mounting fuseholder
1 neon illuminated DPDT
240VAC-rated rocker switch
6 20mm black anodised
aluminium knobs
1 40mm black anodised
aluminium knob
4 plastic PCB supports
Miscellaneous
Twin-shielded cable, figure-8
shielded audio cable, hookup
wire, solder, heatsink compound,
screws, nuts, washers.
With the power amplifier module
complete, carefully check your
work for misplaced parts and faulty
soldering. Do not apply power at
this stage.
Next month, we will show you
how to assemble the two modules
and the power supply in a rackmounting case.
~
_ _ _G_E_T_C_H_A_R_G_E_D_U_P_ _--r-N
- IC_A_D_BA_TT
_E
_R_Y_CH_A_RG_E_
RS~
I
THIS CHRISTMAS
jl, I
"AA"
Nl:~!~!'HICAD. BATTER~~~$2.95ea
(rechargeable up to 600 times)
"AA" ARLEC 500mAH.
. ..... NOW $8.95pr
(rechargeable up to 1000 times)
'
"AAA" ARLEC 180mAH. .
....
. ... NOW $9.95pr
(rechargeable up to 1000 times)
o(
~
~
"C" size ARLEC 1.2AH.
. ......... NOW $16.95pr
(rechargeable up to 1000 times)
"D" size ARLEC 1.2AH.
. ..... NOW $17.95pr
(rechargeable up to 1000 times)
9 volt VARTA 100mAH.
. .......... NOW $17.00ea
(rechargeable up to 1000 times)
6 volt LANTERN RECHARGEABLE
• 6 vo lt <at> 5000mAH
• Complete with charger
for 240 volt & 1 2 volt operation
ONLY
s59.95
• BATTERY AVAILABLE SEPARATELY
oNLY
s29.95
"UNIVERSAL BATTERY
e
)ooG
• ;,":i:,;~,A•RJ!A'!n.~ScT~~••' '''°" ~.~
29
•~
• LED charge indicators
• Voltage level meter
ONLY $
"ARLEC" NICAD CHARGER
"Designed for these remote control cars"
• Do up to 8 x "AA"
and 2 x 9volt cells
• 2 year guarantee
.95
Use your rear
window demister
as a car radio antenna
Fed up with replacing your car's radio
antenna? Your rear window demister
can be adapted to do the job instead.
By JOHN CLARKE & GREG SWAIN
Let's face it - car radio antennas usually don't last very long.
They can suffer a variety of fates.
They can get gunked up with dust
and grime and go open circuit; they
can be bent by some mindless
moron; or they can be damaged by
overhanging branches in your
driveway.
If you have a power antenna, it's
usually not too long before the nylon
gears or the clutch in the drive
mechanism wear out and the antenna jams. When that happens, the
34
SILICON CHIP
antenna is then virtually useless. At
around thirty bucks a hit (or more),
replacement power antennas are
not exactly cheap.
This project is designed to solve
your car radio antenna hassles
once and for all. It's a simple adaptor circuit that lets your rear window demister function as an efficient antenna.
In fact, this scheme will work
much more efficiently than the
traditional coat hanger antenna
replacement. And because the
demister element is attached to the
inside of the rear window it's
vandal-proof, weather-proof and
never needs replacing.
How it works
Unfortunately, it's not simply a
matter of just clipping the antenna
lead to one of the demister terininals. That would be too easy.
There are two problems. First,
we have to isolate the demister element from the supply lines at RF
(radio frequencies). If we don't do
this, any RF signals that are picked
up by the demister will be shunted
to ground via the battery.
Second, we have to keep any high
frequency noise that's present on
the supply lines out of the demister
circuit, while still allowing the
heater current to flow. In an auto
PARTS LIST
L1,L2 : 30T, 1.25mm ENAMELLED COPPER WIRE, BIFILAR WOUND
ON A NEOSID 28-042-31 F14 FERRITE RING
CAR ANTENNA ADAPTOR
Fig.I: the circuit is basically a simple LC filter which is
interposed between the supply lines and the demister element.
Ll and L2 are wound on a large ferrite ring core.
electrical system, high frequency
noise is always present on the supply lines. It is caused by the ignition
system, by switching transients and
by the operation of electrical
motors and .relay contacts.
This electrical noise must be kept
out of the antenna circuit otherwise
it will cause audible interference to
the reception.
Fig.1 shows how this is done. The
circuit employs a simple yet very ef- ·
fective LC filter arrangement which
is interposed between the supply
lines and the demister element.
Both supply lines are first decoupled using 0.22µF filter capacitors
and then fed to the demister element via inductors L1 and L2 which
provide further filtering.
As a result, any high frequency
noise on the supply lines is filtered
out before it reaches the demister
element.
Ll and 12 also provide RF isolation of the demister circuit from the
supply lines. These two inductors
are wound on a large ferrite ring
Three wire straps spaced at 120° intervals are used to secure the toroid core
to the PCB. Note that the toroid is bifilar wound (ie, the two windings are
wound on together). Use shakeproof washers under all nuts.
1 PCB, code SC05-1-1188-1,
72 x 85mm
1 aluminium case, 135 x 75 x
55mm
1 Neosid 28-042-31 F14
ferrite ring core
3 0.22µF ceramic capacitors
1 .01 µF ceramic capacitor
1 1 80pF ceramic capacitor
3 metres heavy duty coaxial
cable (eg 7 50 TV antenna
cable)
6 metres light duty coaxial
cable (for antenna lead)
3 metres 1.25mm enamelled
copper wire
2 500mm lengths of heavy
duty hookup wire
4 solder lugs
4 5mm ID rubber grommets
4 9mm standoffs
1 car radio antenna plug
Miscellaneous
Screws, nuts, shakeproof washers, automotive spade clips.
and provide about lkO isolation between the supply and demister element at AM frequencies and about
lOOkO isolation at FM frequencies.
Note that quite a large ferrite
ring has been specified (25mm ID)
for this circuit. This is to prevent
core saturation due to the high current that flows when the demister is
turned on.
The RF output is taken from one
side of the demister circuit and
coupled to the antenna lead via a
.OlµF capacitor. This capacitor is
necessary to isolate the + 12V supply from the antenna input.
The 180pF capacitor to ground
on the negative side of the demister
has an impedance of about 9000 for
AM signals but only a few ohms for
FM frequencies. This means that,
as far AM signals are concerned,
the demister element functions as a
short wire antenna (ie, short
relative to the wavelength of broadcast AM frequencies). Note: the
wavelength of a 1MHz radio signal
is 300 metres.
At FM frequencies, the negative
side of the demister element is virtually shorted to chassis. The
demister element now functions as
a horizontal whip antenna which is
DECEMBER 1988
35
TO DEMISTER
~
~
L1
y
L2~
Fig.2: here's how to wire up the Car Antenna Adaptor. The ferrite ring is bifilar wound using 30
turns of 1.25mm enamelled copper wire (see text). Use 750 TV cable for the demister connections.
longer than the optimum 1/4wavelength but still functions quite
well.
Construction
The car antenna adaptor is built
on a PCB coded SC05111881 and
measuring 72 x 85mm. This is housed in an aluminium case measuring
134 x 75 x 55mm.
The inductor is wound using
heavy gauge (1.25mm] enamelled
copper wire (ECW). Because the
current flowing through the supply
wires to the demister element is
quite high, the windings must be
I
..
The antenna and demister leads enter
the case through rubber grommets.
Note how the shields are terminated
on solder lugs.
36
SILICON CHIP
wound so that the flux created by
one wire is cancelled by the flux
from the return wire.
This cancellation is achieved by
winding both wires together and by
ensuring that the current in each
wire flows in the opposite direction
to the other.
To wind the toroid, take 3 metres
of 1.25mm enamelled copper wire
and fold in half to give two parallel
lengths of 1.5 metres. They should
then be twisted using a hand drill
until there is one twist about every
5mm.
Now wind 30 turns through the
toroid. The wire should be wound
on tightly with each winding close
to the preceding winding. There
should be a gap of exposed toroid
between the ends of the windings
for about 20° of the radius.
The toroid is secured to the PCB
using three tinned copper wire
straps. Clean and tin the ends of the
leads before mounting the toroid
and make sure that you don't
transpose the ends of the L1 and L2
windings. You can separate the two
windings by using your multimeter
to check for continuity.
After the toroid has been installed, you can solder in the five
capacitors. The PCB can then be
positioned in the bottom of the case
and the four corner mounting holes
marked out and drilled.
You will also have to drill holes in
the sides of the case to accept the
cord entry grommets and to mount
the solder lugs. Fig.2 shows the
details.
The wiring from the PCB to the
demister element should be run using shielded 750 TV cable. This
should have a solid 1.25mm central
core so that the cable can carry the
demister current. The shields are
soldered to the solder lugs mounted
on the case as shown on Fig.2.
Do not use unshielded cable for
these connections otherwise you
will get interference problems. The
antenna lead can be run using 500
coaxial cable (eg, RG58C-U]. Make
the cable long enough to reach from
the rear parcel shelf to the radio
and terminate the free end with an
antenna plug.
Antenna plugs are readily available from kitset suppliers.
Once the wiring has been corn-
Getting at the antenna socket can be difficult on some cars but not on the
Holden Commodore. All you have to do is remove the ashtray. On other cars,
you can gain access to the socket by removing the glovebox.
Do not touch the spade clip
connections to the demister. If they
break away from the windscreen,
they will be difficult to repair.
DEMISTER
pleted, the PCB can be mounted in
the case on 9mm standoffs and
secured using machine screws and
nuts.
Installation
The Car Antenna Adaptor is best
mounted beneath the rear parcel
shelf in the boot, near to the power
wiring to the demister element. On
most cars, you will find two short
wires running up to the demister
terminals from the rear parcel
shelf. The leads are usually plugged
into spade connectors which are attached directly to the windscreen.
Do not interfere with these spade
clip connections. If you do, you
A conventional antenna plug is fitted
to the end of the antenna cable. This
then plugs directly into the radio's
antenna socket.
could pull one of the terminals
away from the windscreen and
damage the demister element. And
that would not be an easy repair
job.
Instead, we suggest that you
break the power leads under the
rear parcel shelf and interpose the
Car Antenna Adaptor there. You
may even find that the power leads
to the demister are conveniently
connected to the rest of the car's
wiring via bullet connectors or a
plug and socket arrangement. Fig.3,
shows the wiring details.
The most difficult part of the installation will be running the shielded antenna lead to the front of the
vehicle. In most cars, you will be
able to hide the lead by running it
along the floor under the door
trims. From there, the lead can be
run behind one of the kick panels to
the underside of the dashboard.
After that, it's simply(!) a matter
of plugging the lead into the antenna lead from the radio (easier said
than done on most cars). A little ingenuity often helps here. For example, on some cars you can gain access to the antenna socket by
removing the glovebox or by pulling
out the ashtray (eg, on the Holden
Commodore).
In difficult cases, it may even be
r
___
SHIELDED CABLEli
,
RAOIO--SHI-EL-DE....
D_ _ _,..
ANTENNA
LEAD
DEMISTER
ANTENNA
TO SWITCHED
DEMISTEh WIRING CHASSIS
TO CHASSIS OR
NEGATIVE DEMISTER
WIRE
Fig.3: how to wire the adaptor
circuit to the demister element.
The unit is best mounted under
the rear parcel shelf.
necessary to remove the radio. A
workshop manual will show you
how to go about this job.
When all is complete, the installation should be tested with the
motor running to check for interference. You should also try turning the demister on and off to
make sure it still works in its
original role.
As a final step, if your car radio
has an external trimmer for AM, it
should be adjusted for best reception at the top of the band.
~
DECEMBER1988
37
,-------------------------~~...;::::,:J
Why Waste Your time With Other Suppliers
I
Altronics Can Deliver Any Of The Quality Products .
1 To You Tomorrow - Just Phone Your Order Toll Free 1
I Jack O'Don
On 008 999 007
·I•
I M/Directo~eII
Country Clients Please Allow Additional 48-72 Hours
I
·I
I
.
~------------------------------Sensational Super Buy On
Quality Sampson 12V
Recharg a I Batteries
This Quality 12V 1.2AH Lead Acid Battery
Sells Elsewhere for $30!
Altronlcs Price?
i:199.oo
Just $15
ltr■ H gh P
er Capacity
Polypr PY e e ••• Driver•
f,) This brilliant little mixing console is absolutely packed with features.
() Allows blending of Microphone. two Phono inputs and either two Tape or
{) Turner inputs • Right and left VU meters • Separate Bass and Treble
/(co ntrols • 5 slide level controls • Fader control between Pho no pick ups for
/ i i professional c ueing • Headphone monitor switch • Talkover facility .
Save 25% Thi• Month
)\ SPECIFICATIONS:
12" (300mm) Model
• Input Mic 0.5mV 600 Ohms Phono 3mV 50K Ohms Tape/Tuner 150mV
100K Ohms • Output 250mV •Frequency Re ■ ponae 20Hz to 20Hz (plus or
minus 1db ) • Tone Control (Treble) 10KHz (plus or minus 12db) • Tone
Control (B ■ -1) 100Hz (plus or minus 12db) • Ol1tortlon Less than 0.07% •
··· S/N Ratio More than 60db • Headphone Impedance 4-6 Oh:ns •
Olmen1lon1 318 (L) x 217 (W) x 85 (H)
100 Watts continuous input
150 Watts intermittent input
Impedance 8 Ohm
Sen■ltlvlty 93db
Weight 3620gm
,))
})
\)
}:(
-o
ol
C 3070
9
9
$
Normally $139
Our sophisti ca ted 'NEW' Audio Mixing Console is ideal for ':ive' recording
• PA mixing • Fantastic Tape recordings • Even Stereo/ Mono VCR
recording . A truly professional deck that features separate R/ L 5 band
graphic equalisers• Echo and Peak LED level indicators• Talkover faci lity
• Separate H/Phone level control • 'Patch switch bank • Individual
microphone, Phono 1 Phone 2, Aux/Line 1, Aux/line 2, and Master slide
level controls. Blend up to two magnetic or crystal turntables, two
tape decks or tuners and two microphones all at once!'
SPECIFIC,\TIONS:
• Input Mic 1-0.SmV 600 Ohms Mic 2-0.SmV 600 Ohms Mic 2-0.SmV
600 Ohms (low imp.) 2.SmV 10K Ohms (low imp.) Phono 1 & 2 (Mag) 3mV
SOK Ohms Phone 1 & 2 (Cry) 150mV 100K Ohms Tape/Tuner 1 & 2150mV
100K Ohms • Equall1er 5 frequency bands-60Hz, 250Hz, 1KHz, 4KHz,
12KHz-Boost Cut range-plus or minus 12db <at> Centre frequency. •
Output 1.5V/0.775V (Selectable) • Frequency RHponH 20Hz to 20KHz
plus or minus 1db • Ol1tortlon Less than 0.05% • SIN Ratio More than 50db
• Headphone Impedance 4-16 Ohms• Echo B.B.D.System • Delay Time
30-200mS • Echo Repeat Control• Delay Time Control• Dlmen1lon1480
/l \ x 240 IW\ X 110 (H\
Mylar Stereo Phones
ith D namIc Mic
Simply brilliant Mylar Stereo headsets &
dynamic mic combination.
Headphone Spees. 20Hz - 20,000Hz,
32 Ohm, 102 db/uW, 3 .5mm stereo jack,
6.35mm stereo jack, adaptor.
Microphone Spees. Dynamic type,
300 Ohm , 100Hz - 15,000Hz, -80 db<at>
1 KHz, 3.5mm MCo9no05ja5ck.
s29.95
a11lve nfra-Red Lit Guard
odllg Co
How often have you thought there could be a prowler
outside your door? Install a LIie Guard & (once armed)
any "guest" wlll be floodllt when detected by thlI highly
sensitive Intra-Red Detector.
Please Note FloodlampI & Holders
Not Supplied
S5350
s135
The lite Guard detects a moving person or vehicle by
comparing the background temperature with a rapid change of
temperature across the detection beams. So when Lile Guard
detects movement across the coverage area, it will turn on the
floodlight(s) for 1-20 minutes aa pre-adjusted.
Specification■: Detector: Dual element pyroelectric PIR sensor
• Raintight outdoor all weather operation. • Photocell to
deactivate sensor during daylight• Operating Voltage: 240V
AC, 50Hz. Operation time: Adjustable 1-20 minutes.
Ser,I1tlvlty: Adjustable 20'-50', 30 beams• Aimable desired
direction with 2 ball joints• switching Capability: 500W max.
,.,.,.,,,,,,,,,
i/=:=:=:=: ='?}')')
---~ ~ ; ;
.. ..
Just Imagine a Security/ Alarm System you can Install In about an hour- Uses no Wiring
or Cables and Costs Less than $1 for the Mounting Hardware
UHF 305MHz Microprocessor Controlled Wireless Security System
Commercial grade, quality alarm systems are expensive-Just phone one of the "Name" security firms and get a quote for your home-our estimate is that
it will be anything up to $1,000 just for the equipment - then there.Ii the ln1tallatlon -countless holes punched through walls, miles of wiring and a day or
two of installers labour and thal'I around$35 per hour then day,. Hardly worth the effort It It? Alter all what have you gotto loon? - Only Iha Video Player
CD Player, Camera, HI FI, TV, Jewellery and-so onll
Well all that 11 now changed - with our brllllantly englnNred Home Guard Wlrele11 Security System
Read On -
Take It With You If You Move
Apart from the flawless operation of the Home Guard System-One of the great features is its application with rented or leased premises-Lets face it,
money spent on installing a wired system in your Home or Office , Factory etc . is irrevocably lost when you move on . With the Home Guard you simp ly
take it with you .
This alarm system is a brand new design that features completely wireless
connection to all accessories, even the reed switches . Think of how easy it
Ideal for the lounge room , family room or
is to install a " Wireless" alarm system . The benefits are endless.
e.g . arming your Flat or Townhouse with an alarm you don 't need to run hallways e.g. anywhere where an intruder is
likely to pass through . Mounts up on the wall or
w ires through the roof or drill great holes through your walls. When
moving house the alarm is simple to dismantle and re-install elsewhere . on top of bookshelves etc . Detects movement
within an area of 9M by 9M by sensing intruder
The system divides protected 3reas into either perimeter zone or internal body heat movement through the protected area
zone , programmable by dip switches in each transmitter/ detector. Pocket Should not false trigger with the family cat or
remote control can simply arm or disarm your house perimeter from your curtain movement etc. - as is the case with the
bedside when retiring etc. this allows essential protection while cancelling
internal zone as desired. Each transmitter/ detector unit can be
cheaper Ultraso;c ~;;~
programmed into interior or perimeter zone . Zones can be programmed
for instant or delayed trip . The system has a built-in ear piercing siren for
intrusion and panic alarm signals
Passive Infra Red Movement Detector
$
129 ■DO
Remote Plezo Siren
System Is Comprised Of :
This unit is an optional line carrier receive r.
Receives signal through ' AC' line i.e. it would
ideally be located in , say , the roof space and
plugged into mains power .
Main Control Receiver
s 52so
s125.oo
Complete System
Special Package Price
One
One
One
One
S
S
S
S
5265
5270
5280
5285
Main Controller
Reed Switch
Passive I/ R Detector
Wall control un it .
• Wireless reception of external or internal sensors or detectors .
• Selectable home or away modes for selecting internal and external
arming or just external to allow movement inside the building
• Built in Piezo electric siren gives different signals to indicate different
functions.
• Sends signal down power line to activate one or more remote sirens .
• Programmable Arm/ Disarm switch buttons.
The main control receiver runs on 240V AC with a 12V 1.2AH battery for
emergency backup . Al l other units with the exception of the line carrier ,
run on a 9V battery each . The average life expectancy is approximately
one year . System works around the 305MHz frequency where there is less
chance of false alarm . The range of the unit is normally 80 metres in open
space .
Alarm and Indication Sounds
Intrusion Alarm - Panic Alarm - Arm Tone - Disarm Tone - Exit Click
Tone - Monitor Tone - Tamperinq Alarm.
Detector/Transmitter Unit (Reed Switch)
Suitable For Windows and Doors
I
11
s499
Nole: For larger installations your system may well require several Reed
Features:
::!::ilil;I!i!:::1:! 1I I1Il
~
s 5260 Normally S570
Accessories
= :•:._'} ,=/==::::':::
/ {=:=· :·,::' =:=·=•.·.........
This Month
This consists of an enclosed reed switch and
compact UHF transmitter and a removable
enclosed magnet. The unit is at rest when
.magnet and reed are side by side {within 25mm
or 1 inch) . When the magnet is moved away
more than approximately 1 inch the alarm
signals to the Main Control Receiver and the
alarm is sounded . In practise the
Reed/ Transmitter is mounted on the door or
window frame with the magnet on the moving
door or window.
s 5210
s55 .oo
switches, movement detectors and 2 or more sirens . Also the remote door
controller and or pocket remote controls could be very worth while
accessories. The fantastic thing about the Altronic system is you simply
add more detectors as you discover the need - no wiring, no e:(pensive
technicians , no modifications to equipment .
Hand Held Control Transmitter Unit
A real joy to use - keep it at the bedside table allows you to, say , arm the house perimeters
when retiring or you can take it with you when
you go out , arming your system after you loc k
the door. Unit is a funct ion control transm itter to send 4 different signals.
Off - To disarm the system before entering .
Home - To instantly arm the system with
'Perimeter' detection only . Away - To arm
complete system after a given exit delay time of
about 40 seconds. Panic - To start an
emergency signal whenever needed, in any
mode.
s 5215
I
I
s59 .DO
Front Door Keypad
Control un·t
This handy accessory virtually duplicates the
function of the Master Controller unit but at a
more convenient location i.e. just inside your
entry ·door etc . System can thus be armed or
disarmed without the need to go to Master unit.
Especially handy for larger homes or offices.
s 5285
s99 .oo,
~ ~ : : : ~ - ~-:;l;;~;
Ja~k/ ~~~~t~~ell
!~ ~;~ ~ ~ ; ;
Great Kit Projects To Build
Many Just Released
Brllllant Performance Stereo Pre Amp
Go anywhere 240V Mains ·
Power fr.om your car or truck
battery with these fantastic DC
to AC Inverters
Studio 200 Stereo Control Unit
(Slllcon Chip June/July'88)
Out-Performs Commercial Units Costing $600 Plus
The Studio 200 Stereo Control Unit is companion to the studio 200
stereo power amplifier (or other power amps) . It features slim single
unit rackmount profile, treble, bass, balance, inpu_t selector, tape
monitor switch, stereo/ mono switch and volume control. Inputs
include phono, tuner, CD , VCR and tape loop.
Power House 600W Inverter
(See EA Dec'87)
A must for farming, camping , mining, boat ing, remote settlements and
wherever else 240V power isn 't available.
Feature■ : Strong custom steel chassis• Industrial grade power coat
finish• Can be configured to operate off either 12Vand 24V DC• Very
little internal wiring • Manual or Auto start facilities • Low battery cut
ou t • Compact Toroid transformer.
Fully Built & Te■ted
K 6770
KIT VERSION
Calling All Audio Purists
This Great New Amp From Silicon Chip Is For You
Studio 200 Serles 100 Watts
Per Channel Power Ampllfler
K 5010
s399
Features: • In-Built speaker protection• Toroidal Transformer
(low hum} • Black Satin Finish• Low leakage power supply capacitors
• Housed in Rugged Custom Chassis.
Specifications:• Output Power 100W into 8 Ohms Freq. Res.(at 1W)
20Hz-50KHz + or - 1db Input Sensitivity 870mV Harmonic Distortion
(20Hz-20KHz) 0.1% Signal To Noise Ratio 100db or Better Protection
5A fuses plus RDE245A Polyswitch Damping Factor (without
Polyswitches) 100 (with Polyswitches) 100. Stablllty Unconditional.
K 6774
12V INPUT
K 6775
24V INPUT
s425 s525
s525
300 Watt Inverter With Auto Start
Operates From 12V Car Battery
Features: Auto start draws power from your battery only when
appliance is plugged in and "turned on" i.e. battery can be left
permanently connected if required. • Voltage regulated • Current
Regulated • Current Overload unit self limits - Single PC Board
construction - easy to build as there is very little internal wiring .
Complete Kit
K 6750
Dlscolite
(See SIiicon. Chip July/ Aug'SS)
Add Some Colour To Your Next Party
s>·•5;;~:.:··
s279.oo
,.,,,,., :,-i•• ••'u " ' ""
The Discolite Flashes party lights on and off in beat with music from
your amplifier.
• 4 light channels controlled by 4 separate audio channels • Forward,
reverse and auto-reversing chaser patterns• Simultaneous strobe on
all four channels • ' Alternatirig light patterns • Music modulation
available on chaser, strobe & alternate patterns• Inbuilt microphone
for beat triggering or audio modulation of lights• Direct inputs for beat
triggering or audio modulation of lights • Sensitivity control • presettable sensitivity levels for each channel • Front panel LEDs mimic
light display.
Great For Parties, Shop displays and special lighting effects.
Transistor FET
Zener Tester
(See EA Feb/Mar'SS)
s49 .95
New updated circuit incorporates
facilities for testing transistor FETs
and Zeners etc.
Features: • Gain • Leakage
• Breakdown Voltages • Zener
Voltage • Polarity - NPN/PNP
:~ . _.;:.:;. . ;~;••----•:::::::::::llll1::::::llll1:: : ■lllllll1:::::::;:[~'.:J-
K 2527
Low-Cost Unit
Checks Values from 1pF -100uF
Upgraded Digital Capacitance Meter
The readout consists of a bright 4-digit LED display and the ful l sca le
readings for each range are 9999.9nF and 99.99uF. No adjustments are
necessary when taking a reading. You simply connect the capacitor to the
test terminals and select the appropriate range . The circuit can accurately
measure capacitance down to one picofarad (1 pF). This is made possible
by the internal null i ng circuit which cancels any stray capacitance
between the test terminals or test leads . So when you measure a SpF
capacitor, the unit will display SpF.
save$$$ 1
1t,e co•
ol\
"'erc\al
ol co"',~alel\ltl
Super Low Price on Famous
EA 8 Sector Alarm System Kit
(See EA Mag,Jan '85)
eQII •
Fe ■ ture1:
• Alarm has 8 separate input circuits - 8 sectors
can be monitored independently.
• Each input circuit is provided with an
indicator LED and a sector On/ Off switch .
" Individual sector isolation allows the user to
have some areas of the premises habited
while others remain protected e.g . Inside
Off/ Outside On.
• Inputs accept both normal ly closed and
normally open sensors.
• Two inputs provided with an entry delay
between 10-75 seconds).
Internal trip warning buuer-alerts owner/
occupant of pending alarm operationgreat for the " forgetful " amoungst us . This
buzzer is pre-settable between 5 and 55
seconds prior to Alarm.
• Unique circuit detects automatically when
any N/0 or N/C loops are either open circuit
or dead short. e.g. oomeone trying to brtdge
Bench Top
Power Supply
3-30V to 1 amp Max.with
variable current llmlt
FEATURES:
* Output 3 to 30V at 1A ~ Short cir cuit
protected• Load switching• Current limiting . Dual scale meter • Housed 1n our
Delu xe " ABS " instrument case
SPECIFICATIONS:
-. Ou t put Voltage - 3 to 30V -. Outp ut
Curren t - 0 to 1 amp (fully variable ) • Load
Regu lation• Better than 0 .2% from Ot o full
KIT
K 3210
load-. Output Ripple-Less than 2mV RMS
reed 1wltche1 etc.
• Switched output can be used to send a si lent
alarm through an auto-dialler circuit or
similar.
S 5065
KIT
(without Back Up Battery)
(12V 1.2AH Backup Battery) Now Only
$15.00
Converter
24V To 12V DC
(Slllcon Chip Dec'87)
Laboratory
Power Supply
Enables 12V appliances like
stereos, 2 way radios, CB's etc. to
operate from a 24V battery.
• Operates from 18V- 30V. Output is
13.6V at 5 amps.
K
~~1s s59 .00
mn
174 Roe St. Perth WA 6000
PHONE TOLL FREE 008 999 007
Perth Metro & Alter Hours (09) 328 1599
ALL MAIL ORDERS
P.O. Box 8350 Perth Mail Exchange W.A.6000
AL TRONICS RESELLERS
Chances are there is an Altronics Reseller right near you - check this list or phone us for
details of the nearest dealer. PIH •• Note: Resellers have to pay the cost of freight and
insurance and therefore the prices charged by individual Dealers may vary slightly
from this Catalogue - in many cases, however, Dealer prices will still represent a
significant cost saving from prices charged by Altronics Competitors.
Don't forget our Expre11 Mall and Phone Order Service - for the coot of• local call,
Bankcard, Yiu or Mutercard holder• can phone order for ume day deopatch.
K3300
3-5 Voll• at up lo 5
Amp■ $
195
Designed by Electronics Australia , this supply has been one of our most popular
kits. Our version incorporates refinements and 1s now housed m an attractive ,
tough " ABS" instrument case. This all new compact version has been made
possible by the use of a highefficiency Toroid Power Transformer. So you win four
ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlc1 Kit 11 fully drilled and punched.
Manufacturers, Contractors and Bulk Users
Please Contact Our Wholesale Sales Dept.
Sydney (NSW Only) Colin Fobister 437 4077'
Perth 09 328 2199
STAN DARO DELIVERY & PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA
WIDE - We process your order the day received and despatch via. Australia Post.
Allow approx 7 days from day you post order to when you receive goods
$7.00 OVERNIGHT JETSERVICE - We process your order the day received and
despatch via. Overnight JelHrvlce Courter for delivery next day Country areas please
allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders).
$10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express
Road - Please allow 7 days for delivery.
INSURANCE - As with virtually every other Australian supplier, we send goods at
consignees risk. Should you require comprehensive insurance cover against loss or
damage please add 1% to order value (minimum charge $1). When phone ordering
please request "Insurance".
TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order
tol l free up to 6pm Eastern Standard Time. Remember with our OvernlghtJelMrvlce we
deliver next day.
WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K.B.Electronics &
Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARR.ATHA Daves Oacitronic 854836 MANDURAH Lance Rock
Retravision 351246 WYALKATCHEM D & J Pease 811132
NT ALICE SPRINGS Ascom Electronic ■ 521713 Farmer Electronic ■ 522987
ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334
VICTORIA CITY All Electronic Components 6623506 SOUTH
MELBOURNE Winscott Trading 6995740 SUBURBAN
CHELTENHAM Talking Electronics 5842386 CROYDEN Truacott Electronics
■ -7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411 4 11 MORWELL Morwell Electronics 346133
QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall
Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321
MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron
World 278988 TOOWOOMBA Hunts Electronics
■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force
Electronics ■ 3770512 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics
■ 3471188 COUNTRY MT.GAMBIER South East Electronics 250034 WHY.ALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey
■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171
NSW CITY David Reid Electronics ■ 2671385 CAAINGHAH Hicom
Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY COFFS HARBOUR Coffs Habour .
Electronics 525684 ° .
· NELSON BAY Nelson Bay Electronics 813885 NEWCASTLE Novocutrlan Elect.Supplies
■ 621358
NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935
WOLLONGONG Newtek Electronics ■ 271620
_
B_lue R_lbbon Deal~ro are highl ighted with a
■.
These De_alers generally carry a comprehensive range of Altronic products and kits or will order any required item for you.
Because standard insulating bushes were used, the
heatsink bracket was spaced off the board. The bracket
should sit right down on the board .
The required insulating sleeves for the heatsink assembly
can be made by cutting off the washer portion of the
insulating bushes using a utility knife.
• •
IDIC
•
Kit Clinic is an occasional feature which takes a
look at readers' problems with SILICON CIDP
projects. It is published to help other readers who
may experience similar problems with the same
projects.
Dear SILICON CHIP,
I have built three 100 watt power
modules as described in the
December 1987 issue of SILICON
CHIP. All three modules are gutless;
they don't deliver any power to
speak of. I've noted that the power
transistors don't get hot but the protection thermistor does get very hot;
this when attempting to drive the
modules to full power. Otherwise,
the amp modules seem to working
OK.
• When we had a look at one of
this reader's amp modules we were
reasonably encouraged. Superficially, it was quite well constructed although not to the letter
of the article; there were a number
of specific deviations. These were
as follows.
42
SILICON CHIP
First, the assembly of the power
transistors and heatsink bracket
onto the printed board wasn't right.
Instead of the heatsink bracket being flush down onto the printed
board, it was spaced up by about
1mm.
This was because the reader had
used standard insulating bushes instead of the insulating sleeves
specified in our heatsink assembly
diagram. He could have made the
required sleeves by cutting the
washer portion off the insulating
bushes. (Our photo shows how you
can do this with a utility knife).
We also found that none of the
screws retaining the power transistors and heatsink bracket were
tight. One screw was decidedly
loose and there was a noticeable
gap between the heatsink mounting
surface and the bracket. The heatsink screws need to be tight otherwise the heat transfer from the
transistors will be poor and they
will overheat.
Fixing this problem was not simply a matter of tightening the screws
because the base and emitter leads
were soldered to be board. Tightening the screws would either bend
the board or the transistor mounting flanges. Inevitably, the latter
happened.
To correct the problem properly,
we had to desolder the base and
emitter leads of all four power transistors, tighten the screws and then
resolder the transistor leads. We
did not bother to correct the heatsink bracket assembly - time is a
problem at SILICON CHIP.
Solder connections
We then checked all the soldering on the board very carefully. A
number of the solder connections
were suspect because the component leads were not properly tinn-
Don't leave the small signal transistors at full lead length.
Push them down close to the hoard so that they cannot
be bent over and their leads shorted.
ed. This did not mean that the components concerned were not connected into circuit. At some time in
the future though, these connections probably would have played
up.
Having checked all the soldering
we connected a power supply
( ± 40V DC) and checked voltages in
the circuit. Everything seemed to be
OK except that the quiescent current (the current drawn by the
amplifier when no signal is present)
seemed to be too low (less than 10
milliamps). This was checked
by connecting a digital multimeter
between the emitters of Q12 and
Q13. The measured voltage was
flicking between 1 and 2mV DC.
Using Ohm's Law, we divided
2mV by 0.440 (the total resistance
between the emitters of Ql 2 and
Q13) to get a calculated current of
4.5mA. Allowing for the fact that a
similar current should be flowing
through Q 10 and Q 11, the total current would have been less than 10
milliamps.
Accordingly, we tweaked trimpot
VRl to obtain a voltage of 11mV DC
between the emitters of Q12 and
Q13. We checked that the voltage
between the emitters of Q10 and
Ql 1 was very similar. We could
have checked the quiescent current
by the procedure set out in the
original article, using 5600 resistors across the fuseholders. We used to quick method to save time.
The RDE245A thermistor (left) must he used with the
high-power module. It is about 20mm in diameter and
blue in colour. Do not use the smaller RDE115.
Now we could proceed to a the published spec. All that was
power check. The unit was con- needed was the correct PTC
nected to a dummy load resistor of thermistor.
By the way, the RDE 115 ther80, with a rating of several hundred watts. We then fed in signal mistor is about 11mm in diameter
and watched the output on an and yellow in colour. The RDE245A
oscilloscope. Sure enough, the unit thermistor is much larger; 20mm in
was not delivering the full quid diameter and blue in colour. It can
only a few hundred milliwatts in be clearly seen on the cover of the
fact.
December 1987 issue.
We then touched the PTC protection thermistor and yep, it was Other comments
stinking hot. This was because the
We noted that the small signal
thermistor was high in resistance . . transistors were installed with
It was in "protective" mode. Then their full lead length. We prefer to
the penny dropped. It was the see these transistors pushed down
wrong PTC thermistor for this into the board and soldered so that
amplifier module.
their lead length is no longer than
The reader had built the high- about 5mm or so. This makes them
power version with four output much more rigidly mounted. When
transistors but had used the RDE they are installed with long leads,
155 thermistor intended for the they can be bent over so that their
lower power module which is leads short and thus cause the
designed to deliver 50 watts into amplifier to malfunction.
40. For this higher power module
Interestingly, if the thermistor
the correct PTC thermistor is the had been the correct type, the
RDE 245A.
module would have been able to
To check that the module could deliver the full power. If it had been
deliver the full output we just driven to full power though,
shorted out the thermistor. Now we chances are that one or more of the
were able to get just on 50 watts in- power transistors would have
to 80 or 100 watts into 40. Har- seriously overheated and perhaps
monic distortion at mid frequencies blown.
and medium power outputs was
It also seemed that the supplied
less than .01 %, depending on how thermistor was now "tripping"
the leads connecting to the module prematurely. Whether it had
were arranged.
become faulty because of long and
As far as we were concerned repeated efforts to get the amplifier
then, the module was well within to do its stuff we cannot say.
.~
DECEMBER 1988
43
THE WAY I SEE IT
By NEVILLE WILLIAMS
Would you please pass the
salt? I need a few grains!
If there's any truth in the old saying about
accepting dubious propositions "with a grain of
salt", some of the statements that have been
bandied around recently in the context of video
and audio are surely calculated to increase
considerably one's intake of sodium chloride!
First up, there's the dicey business of moving TV
channels into the UHF band.
In fact, this rather cantankerous
heading and introduction was triggered by yet another discourse
from TV presenter Bill Collins, on
the subject of computer coloured
films. The same theme has been
repeated so many times in so many
places that it's difficult to treat it as
seriously as some would apparently
wish.
But more about that later.
Even before I had time to put
finger to keyboard, that particular
topic was overtaken by an unexpected update from the Illawarra
area, along the southern NSW
coastline, where broadcasters, service organisations and viewers are
currently in the throes of changing
over to an all-UHF system of TV
broadcasting.
(This same area provided the setting for the "Serviceman's Log" in
October last and the accompanying
map may be of assistance to interstate readers).
I discussed the reasons for the
changeover in the May issue of
SILICON CHIP, under the heading:
"Is UHF TV Really as Good as it's
Cracked Up to Be?" A follow-up
item "The Switch to UHF TV on the
44
SILICON CHIP
NSW South Coast" appeared on
page 37 of the October issue.
Most readers should still have
the articles on hand so I will resist
the temptation to re-state their contents. In both articles, I expressed
misgivings about official attitudes
and the possible implications for
some viewers currently dependent
on the VHF transmissions.
Hence the heading on the May article, as above, and the reservation
expressed on page 17:
"How reception will compare
across the total community remains
to be seen. I'd be surprised if there
weren't plenty of complaints over
the first few months".
The problems take shape
That observation is already looking like an understatement. Since it
was written there has been rising
apprehension among those who are
actually coming to grips with UHF
TV in the area, culminating in what
have been dismissed by some as
"alarmist" statements locally and
in the regional press.
When brought to my notice, I
could think of no better person to
contact than Jim Yalden (VK2YGY),
a TV serviceman who works in the
area. Not only is he actively involved and well informed about the
local scene but his practical experience dates back to a lengthy
stint in the UK, when UHF colour
television was being established
there around 1970.
Having acknowledged that some
of the stories doing the rounds were
"alarmist", Jim went on to describe
a situation that, itself, seemed to me
to be nothing short of alarming for some viewers at least!
Since I first discussed the matter
with him, earlier in the year, he and
his fellow servicemen have been
busily installing UHF antennas in
the Illawarra area and observing at
first hand reception from the three
main UHF transmitters on Knight's
Hill, near Wollongong, all currently
operating at full power. As I write,
the antenna(s) have yet to be reinstalled on a somewhat taller mast
on the same site but the results
so far have been anything but
encouraging.
The additional height may help
but then again, it may not. Recently,
an engineer from a major Sydney
TV station mentioned to me a situation that he'd come across in a middle east country. Having installed
the antenna on a lofty tower
dominating the flat desert-like
countryside, engineers expected
the signals to " go on forever". Instead, the coverage was described
as "pathetic".
The situation improved dramatically, however, when the antenna
was lowered from 300 metres to
less than half that figure.
Fig.1: this map shows the area
affected by the changeover to UHF.
Despite high power, shadowing and
severe fading are causing problems.
The problem was apparently due
to atmospheric ducting and while it
involved VHF signals in that instance, something similar could
conceivably affect UHF transmissions.
Limited coverage & fading
As matters stand on the NSW
South Coast, the UHF signals are
proving to be noticeably less accessible in remote or shadowed
areas than the existing VHF service
and that alone may affect a lot of
viewers.
No less disturbing is the fact that
the UHF signals appear to be subject to periodic fading, presumably
due to fluctuating atmospheric conditions over the relatively long
signal paths involved. The fading is
much more noticeable than was encountered by Jim Yalden in the UK,
or by one of his fell ow servicemen
in Canada and the USA.
Time and again, Jim said, installers have measured · the field
strength at a customer's home,
before erecting a UHF antenna.
When they've returned later with
the hardware, they've been faced
with a totally different reading.
At Jim's own home, about 80km
from the Knight's Hill transmitters
but otherwise well sited, he
receives a relatively good picture,
at a signal strength that averages
about 800 microvolts. But it swings
periodically through a range of
about 6dB. For other viewers, in
poorer locations or further out, the
fading spells the difference between "watchable" signals and
periodic complete "blank screen"
drop outs!
A proposition, accepted in the
area, is that planning has proceeded on the broad - but technically
dubious - assumption that, given a
substantial increase in ERP (effective radiated power), the reach of
similarly sited UHF transmitters
should roughly approximate that of
their VHF counterparts. Accordingly, the new ABC UHF transmitter is
rated at 600kW and the commercial WIN-4 at the maximum permissible lO00kW; this compared
with the 100kW limit for VHF.
But things aren't working out
that way in practice because of
manifestly different UHF propagation characteristics, the unexpectedly severe fading effects and
the fact that comparable field
strength is not good enough. At
UHF, typical domestic receivers require a larger signal to ensure a
clean picture, around 500µ V rather
than 200µV.
Expecting too much?
Jim Yalden expressed the convic-
UHF TV -
tion that many people have a quite
unrealistic impression of overseas
UHF TV services. In Britain, for example, the industry tends to regard
30-35km as "deep fringe".
At Winchester, he says, about
90km from London, there was no
trace of the 1-megawatt London
transmitter and no one expected
otherwise. Where he was staying,
just out of Winchester, a good
signal was available from a 500kW
transmitter on the Isle of Wight,
25km away. But the house was on
the advantaged side of a local hill.
Viewers a few hundred metres
away on the other side of the hill
weren't so fortunate.
When visiting a relative in
Somerset three years ago, TV
reception, according to Jim, was
"dreadful" . And there were plenty
of other places that were no better;
in Wales and parts of Scotland for
example.
So Britain still faces TV coverage
problems, despite something like 70
base transmitters and a host of
translators serving the relatively
compact country.
By contrast, in the NSW 11lawarra area, 30-35km has long
been accepted as little more than
an average viewing distance for
VHF, with the "deep fringe " more
like 100km out. That's the sort of
expectation that the new UHF service is supposed to live up to, with
one base transmitter per channel
and a handful of scattered translators.
Add to that hassles about the
siting of translators and an alleged
Questions and Speculation
• If UHF coverage, as planned,
proves to be inadequate, will the
DOTC support the installation of
extra translators, as necessary, or
will isolated communities be expected to install their own, or rely
on transmissions from the satellite?
• Some maintain that the mid
north coast area will pose even
greater problems at UHF than the
lllawarra area, by reason of the hilly plateau between the mountains
and the sea. Will the DOTC reexamine UHF technical planning
for that area, in the light of the
emerging situation south of
Sydney?
• In the ultimate event of a
3-network commercial system
covering the whole of Australia,
will the participants be obliged to
serve isolated communities as well
as the larger population centres?
• To what extent will viewers
Australia-wide, who may be disadvantaged by a changeover from
VHF to UHF, be supported by the
Government or be obliged to rely
on their own resources?
DECEMBER1988
45
THEWAYI SEE IT - CTD
lack of commitment by the incoming
major commercial networks to the
fringe areas and the immediate prospect for some remote or isolated
pockets of viewers is anything but
rosy. Not only may they not receive
the incoming networks - if and
when they materialise - but they
stand to lose one or both of the existing services.
Problem areas which have been
specifically mentioned range froin
deep pockets in the immediate area
of the main transmitters, to
Kangaroo Valley in the west and to
Bateman's Bay in the south. These
areas presently get by with a patchwork of VHF signals, direct or via
translators.
In the face of those and other
situations, according to Jim Yalden,
there's likely to be "one almighty
hell of a scream" on the day they
switch off the channel 4 and 5A
VHF transmitters - maybe in
January or March; who knows?
She 'II be right, mate!
That's about where we left matters on the morning of September
26, after a couple of phone calls
and a round-robin "rag-chew" on
the 2-metre amateur band. But on
Wednesday the 28th, the MiltonUlladulla Express carried an
assurance by the Federal member
for Gilmore, John Sharp, to the effect that no viewer in the MiltonUlladulla area would be disadvantaged by the imminent changeover
to UHF.
It sounded like a political promise
of the kind that his constituents
most wanted to hear but it was
reportedly based on a firm
assurance from the Department of
Transport and Communications.
When asked whether everybody in
the south eastern television market
would receive improved or at least
comparable services next year,
their reply was an unqualified
"Yes".
Said Mr Sharp: "They have
assured me that many people will in
fact receive improved service and
certainly no one will lose what they
already have, even if this is only a
relatively poor existing signal".
While some viewers may have
been reassured, I gather that the 11lawarra technical bods reacted
otherwise. But unlike the one-time
gentry with their snuff boxes, they
are passing around pinches of
sodium chloride!
How could the Department
possibly give such an undertaking
in view of the limited penetration of
UHF signals, the unresolved fading
effects, the distances involved and
the strictly limited number of
translators envisaged?
Perhaps even Mr Sharp was
reaching for the salt cellar when he
added [as quoted): "I will certainly
remember this guarantee and it is
gratifying the Department has finally been able to provide such an
assurance".
In the meantime, I did not invent
the questions posed in the accompanying panel. I've simply summarised what has been put to me. See
what you think.
Colourising B& W films
From UHF TV I return to the subject of computer-aided colour
reprocessing of black and white
films mainly intended for presentation on television.
Faced recently with the screening of such a film (correction, video
tape), TV presenter Bill Collins
launched into the usual apologia,
acknowledging objections to the
process voiced by some film makers
and reminding purist viewers that
they had the option of turning off
the colour and viewing the original
monochrome image.
How much longer do we have to
put up with this tedious preamble at
every mention of a computer colourised film? I seriously doubt that
many viewers would have followed
Bill Collins' suggestion to kill the
colour - or that he really expected
them to.
Because I had other things to do,
I didn't watch the feature right
through but I did view it for long
enough to register whether or not
the colour was so patently artificial
as to compromise the original image. In fact, from what I saw it was
ordinary enough for a non-alerted
viewer to accept it as just another
colour print.
That was certainly the aim back
in 1977, when the first-ever computer colourised documentary
footage of World War II was intercut with new footage in a mini
series on Dwight Eisenhower ,
featured by the ABC [American
Broadcasting Company). Millions of
viewers didn't notice the difference
between the two, simply assuming
- if they thought about it at all that the documentary material had
also been shot in colour.
For Ralph Weinger and Donald
Havens, credited with the early
development of the system, it was
exactly the reaction they wanted.
Despite this, quite a few film
makers, actors and purists have
condemned the process as akin to
sacrilege and sought to raise legal
barriers to restrict its use.
Sure, serious black and white
photography may qualify as an art
form, with an arguable right to be
respected as such. Some actors
may also reasonably object to their
person and work being artificially
prettied-up and time-shifted out of
the era in which they worked. One
can't blame the various parties for
pursuing whatever rights they may
have in the matter - but enough is
enough.
The fact is that most early films
were shot in black and white
There's likely to be one almighty hell of a scream on the day
they switch off the channel 4 and 5A transmitters
maybe in January or Morch; who knows.
46
SILICON CHIP
because colour was not a viable option at the time. When they appear
on the TV screen today, the lack of
colour is a constant reminder of
their age - like a travelling subtitle: "This is an old film, to be watched only as a last resort".
Many such films may not be
suitable for present-day showing,
or of sufficient merit to justify expensive reprocessing. But where
they are, let's drop the apologetics
and enjoy to the best possible advantage the cinematic products of
other days.
Let's be thankful for modern computer and digital technology which
makes it possible to minimise some
of the print faults in old "flicks", to
reconcile dissimilar frame rates,
clean up noisy sound tracks and
add credible colour. That way, they
might be justifiably rescued from
musty vaults or from TV time slots
in the wee, small hours.
Optical fibre links
But enough of television, films
and video tape. Here's something
for audio types to ponder.
That well known hifi buff, Auric
Lugg, has discovered that thanks to
the near-magic of solid-state integration, opto coupling components for audio systems have
become available: small, efficient
and (for him) affordable.
He looks quizzically at the cable
links between the various components of his domestic hifi system.
They're good quality cables, every
one of them tipped with gold-plated
plugs, fitting into gold plated
sockets. Inductance, capacitance
and resistance are demonstrably
much too small to adversely affect
the signal.
But Auric Lugg's curiosity knows
no bounds and he invests in two
sets of the new opto couplers, along
with two half-metre lengths of
suitably terminated optical fibre
cable. Following the instructions
very carefully and very methodically, he substitutes the new opto
coupling devices for the original
metallic sockets and cables feeding
the main amplifier.
This done, he switches on and
professes to be absolutely amazed
by what he hears. The difference is
not of the subtle kind, revealed only
by careful A-B testing. It's as if a
veil had been lifted from between
him and the loudspeakers. The
sound, he says, is dramatic, stunning, unbelievably pure!
The noise, distortion and unmusical harshness characteristic of
wire connections has been totally
eliminated by installation of the
fibre optic cables, which are claimed to be completely free from such
imperfections.
I jest? I'm letting my imagination
run riot? No! I've simply assembled
a word picture from phrases currently being used to promote the
provision for optical links . in the
latest generation of up-market
audio gear.
You can swallow it if you like.
Me? I'm taking it with a grain of
salt.
Fibre optics are OK
I am not by any means opposed to
fibre optics, as such. It stands out
as a breakthrough in communications technology.
• The National Australia Bank,
for example, has installed an optical fibre network in its Melbourne
administrative centre to interconnect computer terminals, the communications network and the
building control system.
• Optical fibre ea ble has been
laid around Sydney Airport to link
the various radar transmitters with
the operations centre. Unlike the
coaxial cable which it replaces, it is
inert to humidity, corrosion, earth
loops, electrical noise and lightning
strikes.
• Optical fibre cable was chosen
in preference to coaxial cable to bring together at the control building
the very wideband signals from the
0
six mobile dishes forming the
Australia Radio Telescope at
Culgoora.
• Over the next few years,
Australia's internal and external
communications will become progressively more dependent on optical fibre cables.
• In the October issue, I reasoned
that the concept of "fly by wire"
should be replaced by "fly by optical fibre" in the quest for greater
safety.
In short, fibre optic technology
offers considerable advantages in
terms of economy (especially over
long distances), physical durability,
exceptionally wide bandwidth, high
traffic density and a high degree of
immunity from electromagnetic interference, natural or man-made.
None of those advantages has
any obvious bearing on the transfer
of audio signals over the metre-long
(or less) paths in a home hifi system.
It may be trendy but I fail to see
how the substitution of an optical
link for a normal, adequate wire
link can contribute anything to the
subjective quality of the signal.
In due course, mass produced optical fibre hardware and connecting cable could conceivably
become tidier and easier to handle
than shielded copper cable. It may
also get designers off the hook by
isolating signal paths from considerations to do with equipment
earthing (or non-earthing) for safety
reasons.
In the meantime, optical links
may provide a novel sales feature to
distinguish the latest models but as
an effective way of removing yet
another in that seemingly endless
sequence of acoustic veils, I'd need
to be convinced.
~
ft~
uo/.
,,~
.
~
:..OU
rll;
uv1
-
~
"CJIIPIIII""~
RCS Radio Pty Ltd is the only company which
manufa.ctures and sells every PCB & front panel
published in SILICON CHIP, ETI and EA.
651 Forest Road, Bexley, NSW 2207
Phone (02) 587 3491 for instant prices
4-HOUR TURNAROUND SERVICE
DECEMBER 1988
47
ONLY 3 WEEKS
TO 601
Ho Ho Ho. That's Santa laughing at all the bargains he's picked up at his
friendly Dick Smith Electronics store. Santa knows that Dick Smith
Electronics has everything for the electronics enthusiast - and much,
much more besides!
Christmas morning and you forgot the batteries!
Wouldn't you be popular? All those wonderful new Wizz-bang goodies and not a
battery to make them Wizz and bang! Plan ahead - if you get batteries early, you
won't forget. And if you get Nicads, they can be all charged up and ready to fire .
•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
USE NICADS: THEY'RE CHEAl'ER!
Sure they cost more than ordinary batteries. But you can charge Nicads hundreds of times so compare the
price of hundreds of ordinary batteries! You'll save
................................................................
Standard Nicads
TOOLS ARE ALWAYS TREASURED!
180mAh
..AAA" Size
Cat S-3305
..AA" Size
500mAh
Cat S-3300
'C" Size
"D" Size
1.2Ah
Cat S-3301
"9V" Size
110mAh
Cat S-3309
1.2Ah
Cal S-3303
s495
s475
$1195
$1195
S1695
High Capacity Nicads
600mAh
S!j95
"AA" Size
Cat S-3312
2.0Ah
..C" Size
Cat S-3311 s1495
4.0Ah
"D" Size
Cat S-3310 s1595
"SubC" Size
GELL CELLS Ideal for alarms & general purpose usage.
12V
12V
1.2Ah
1.9Ah
35
37
95
Cat S-3315 1
95
CatS.J3t61
12V
12V
2.6Ah
6.5Ah
3895
Cat S-3320 1
CatS-3322
'5595
CHARGERS
TO SUIT:
ln-situ or loose • these chargers will see your NiCad batteries right!
Plug-Pack:
Standard:
Super:
Suitable for most general purpose
in-situ (ie batteries stay inside
device) charging. Handles 6 to 10
standard or high capacity "AA"
cells. Cat M-9517
Handles all types and sizes of
Nicads from AA through to 9V;
charge up to 8 cells at once.
Automatically senses size. includes
charge test meter Cat M-9505
Specifically for high capacity
N1cads; also sences size and
adjusts charge automatically. (Do
not use for standard Nicads except
AA Size). Cat M-9506
-1~
s3995
FUNWAY: THE BOOKS
$495
Fun Way Into Eleclronlcs Vol 1.
20 exciting projects to build• no soldering. Cat B-2600
Fun Way Into Electronics, Val 2. 20 more fascinating proiects •
and we teach you to solder. Cat B-2605
The Ultimate Hi-Tech Present
A Computer! But not just any computer• a superb ACER 500+
from Dick Smith Electronics. Australia's best value in an IBM
compatible - and our low prices INCLUDE a beautiful soft-white
monitor.
Three models to choose from. you choose the configuration you
want to suit your needs. And don't forget, you can always upgrade
your ACER later!
Acer 500+ Complete
from only
s995
Fun Way Into Elllctronics, Val 3.
5695
$695
10 "high tech" projects using integrated circuits. Cat B-2610
INTO RADIO? TRY A SCANNER
The Ultimate: FRG9600
__. ·
What a scanner! It
Hand-Held Action:
Bearcat 100XL
covers all UHF from
300 to 950MHz - so it
~t
includes virtually
evervthing you want to
NORMALLY
$1199
hear! Programmable,
UNTIL XMAS JUST
memories, even
controllable!
The go-anywhere scanner that
means you can actually go to the
action while you 're listening! Full Normally s399
UHF band coverage (to 520MHz),
inbuilt memories, rechargeable UNTIL CHRISTMAS
nicads and AC charger.
cat D-28t3
JUST
!~~~~~f:t
g~ri~?ls
: Now available at 60 stores:
• NSW • Albury 218399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Brookvale
(Warringah Mall) 905 0441 • Campbel-.i /046)27 2199 • Chabwood Cha9e 4111955 • Chullora 642 8922 • Gore HHI
439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • MaiUand 33 7866 • Miranda 525 2722
• NewcasUe 611896 • North Ryde88 3855 • Parramatta 6892188• Penrilh (047)32 3400• Railway Square 2113777
• Sydney City 267 9111 • Tamworth 66 1711 • w ~ 28 3800 • ACT • Fyshwick 80 4944 • VIC • Ballarat 31 5433
• Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • Easl Brighton 592 2366
• Essendon 379 7444 • Footscray 689 2055 • Frankslon 783 9144 • Geelong 43 8804 • Melbourne City 326 6088
• Richmond 4281614 • Ringwood 879 5338 • Springvale5470522• QLD • Brisbane City 229 9377• Buranda3916233
• Calms 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Soulhport 32 9863
• Toowoomba 38 4300 • Towns,rille 72 5722 • Underwood 341 0844 • SA• A - City 232 1200 • Beve,ley 3471900
• St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA • Cannington 451 8666 • Fremantle 335 9733
• North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977
sggg
$369
NOW AVAILABLE AT ALL STORES - OR CALL
TOLL FREE: (008) 22 6610
FOR HOME DELIVERY!
AND THE
WINNER
IS
■
■
$1000
We don't know! No-oae yet has claimed the $1000 bonus from the one
millionth Fun Way Into Electronics kit. Which means one of two things
(a) It's still out there in a Dick Smith store or reseller. or even the
DSXpress order centre. In which case. you could still be the winnerlll
[bi It's been bought as a Christmas present and the winner won't know
until he or she opens it up on Christmas morning. In which case. we say
congratulations!
Just in case it is still out there. why not duck out. duck into a Dick Smith
Electronics store and duck over to the Fun Way into Electronics kits.
Grab one and you still could grab a thousand dollar bonus!
PS: Afinal clue. The one millionth kit also happened to be the most
popular Fun Way into Electronics kit. The $1000 bonus cour.n was
sealed inside the kit. so you can't cheat! That narrows the field down
pretty dramatically. doesn't it.
■
BONUS!
Permit Nos: (NSW) TC88/2231 (ACT) TP88/7914
A " must" for the
service shop,
technician, lab etc.
Instant digital
readout of all
capacitors (electros
included) usually
"in situ". Great for
checking out that
cranky bypass
without surgery! Cat
Q-1222
Low-Cost
Digital is
High Spee!
All usual
multimeter
functions PLUS it's
a transistor and
diode checker,
battery checker
AND a continuity
checker - all in one!
Cat 0-1445
sggss
DON'T GET CAUGHT
THIS CHRISTMAS!
The experts (and statisticsl say the light fingered larrikins are loitering at this
time of the year• with intent! Dim't let your Chrisbnas goodies become the gleam
in someone else's eye: install your own quality Dick Smith Electronics alann
system. You'll save -and save!
,.,.....,,..""""""'= ='i'P1 Hl!YI!
DSE'SOWN
4SECTOR
CONTROLLER
-.
199
And a small selection of detectors & accessories:
Doorway/
Corridor
Beam
S129
Invisible infra-red
beam for protecting
anywhere people
walk. Set for lock
on or instant mode,
buuer or silent.
Cat L-5050
Long Range
lnfrared
Up to 25m range
~~~r~9o~. ~~~) so
you get maximum
coverage. Very fine
tolerance
adjustment for
minimum false
alarms. Cat L-5013
Perfect for flats,
homes, etc where
the area is not
huge. Up to 6 x 6
metre protection
zone, angled
~:fl~~~&r aiming. $
~f~~r~~1~efirst!
The horn cover
protects the horn
speaker and gives
tamper protection .
Cat l-5300
/
8995 1/R Floodlights
Horn Cover ~
A smart thief will
try to disarm your , ·
. ~
·
-
~ I ~~
~
,
,
$2395
Senses any
movement and
turns on floodlights
for predetermined
period (up to
18mins) Ideal for
visitor welcome,
security alarms,
etc. Outsidefins1de
use, all hardware
included but no
floodlights.
with a set of probes ready for action!
But even more, this one has an inbuilt
component checker so you can use it
almost as easily as a multimeter - and
with much better res ults - to check all
types of components.
If you're looking for the ultimate
Christmas gift (even for yourself???)
this must be IT! Cat0-1260
1/)J!:i,O'; ~~
S
Have you got your coloured lights all ready for Christmas - it's
only a few weeks away (bet that scared the pants off you!).
Christmas (and any other) parties take on a whole new atmosphere
with the right lights - and here are the right lights:
Par 38 Heavy Duty
Pressed Glass
R95 Light Duty
Reflector Globes
$10.95 ea
$6.95 ea
Yellow
S-3850
Red S-3852
Blue S-3854
Green S-3856
Yellow
S-3851
Red
S-3853
Blue
S-3855
Green
S-3857
h
;-~h • i .;/, ~- -~-,-· ;-,,~.)-}::,. ,
Every possible combination of lighting spectacle is yours with the
CtK
D1sc0Lite.
a -3150
$
Another great new project from Silicon Chip
Rexible
Cable
165
~
-
Standard 3-core 10
amp flexible cable
for general purpose
use. Grey
insulation .
$
1/m
Cat W-2055
Builders
Cable
Standard 3 core
(insulated earth) 15
amp buildinij cable
for "festoon type
lighting or general
purpose building
use. White
insulation.
···············•·
Edison Screw Lampholder to Suit: Cat P-5620 $7.95
~
~
Economy
lnfrarelf
;
paair~n:~:n d1ss;~o~~th theM~;.cf}1~~~~~;;~an a1~o~o~i1~~ . i
LOT!
L
HERE COMES CHRISTMAS!
Special Introductory price: Just S
~i~/~~~c!n~r~f~s~~~~f ~~~~\~ Ji:P~!te
f
Christmas comes but once a year (with its parties and
celebrations). Turn your Christmas, New Year and every other
COLOURED LAMPS, HOLDERS
AND CABLE TO SUIT ...
A brand new design featuring 4 Individually controllable
sectors, home and away states, wire-out protected loops
and state-of-the-art circuitry. Housed in heavy duty steel
case, ready to install with your choice of alarm detection
devices (uses all standard devices). Cat L-5140
.l1P'?'"m
Build Your Party A Lightshow!
HOW ABOUT
ACRO?
ea
Cat W-2060
Merry Christmas and a
bright and prosperous
New Year ... from all at
Dick Smith Electronics.
♦
♦
♦
♦
♦
♦
♦
♦
DIESEL SOUND
GENERATOR FOR
MODEL RAILROADS
This Diesel Sound Generator produces
the deep throbbing sound of today's
modern diesel electric locos, complete
with turbo boost and alternator whine.
By GREG SWAIN & JOHN CLARKE
While today's model railroads
can look startlingly realistic, the illusion is not helped when those
locos start to move off with a heavy
train behind. Instead of the
penetrating sound of turbo-charged
diesels with wide-open throttles, all
you hear is the tinny sound of
miniature motors and gear mech-
anisms - nothing like the real
thing.
If you're modelling in O scale
(43:1) or HO (87:1) it is possible to
build sound generator circuits into
the loco or a following wagon but
they always have a problem.
Because they can only use the
smallest of speakers, they just don't
have enough grunt. They're not
loud enough and their bass output
is non-existent. ·
And if you model in the increasingly popular N-gauge (160:1), an
on-board sound system is completely out of the question - the rolling
stock is just too tiny.
So we've had a look at the problem of sound for model railroads.
Our new Diesel Sound Generator is
the answer. It can be used with any
scale loco and does not rely on teensy speakers built into the loco. It
uses one or more speakers, as large
as you like, dotted around your
layout. And it incorporates circuitry to monitor where your loco is
so the sound can follow it around
the layout.
We built the diesel sound generator into a plastic instrument case but you can dispense with the case and simply
mount the PCB under your layout. The amplifier PCB is housed in the small plastic case at right.
50
SILICON CHIP
The Diesel Sound Generator is
designed to mate with the
Railpower train controller described in April 1988 but can be used
with any train controller that
varies the track voltage (that leaves
out Command Control systems). It
requires little wiring to add it to
your layout and you can build it in a
simple or more complex form to suit
your needs.
So what sort of sound do we get
from a real life diesel locomotive?
The sound is really quite complex
but consists mainly of lowfrequency exhaust beats and turbocharger whine, coupled with a
small amount of high-frequency
alternator hum. Our circuit simulates all these effects to produce a
very realistic diesel loco sound
indeed.
But we haven't just settled for a
circuit that makes realistic diesel
loco sounds. That wouldn't be good
enough. For starters, this new
design automatically adjusts the
pitch of the diesel exhaust according to the throttle setting. It does
this by constantly monitoring the
track voltage.
The circuit also automatically adjusts the volume according to the
location of the loco and can even
vary the location of the sound
source. It does this by using
trackside sensors to monitor the
location of the train on the layout.
This information is then fed into the
circuit to produce the appropriate
response.
12VAC
TRACK
SOUND GENERATOR
4
DC
3
CONTROL 2
+12V
GND
SIGNAL
SINGLE
AMPLIFIER
TRAIN
POSITION
SENSORS
1 2
4
□
osE~SOR
Fig.1: this is the layout to go for if you intend using a single
amplifier and loudspeaker. The sensors monitor the location of
the loco on the track. This information is then used to derive a
DC control voltage which sets the amplifier volume.
Alternative layouts
Figs.1 & 2 show the two basic
layouts you can use for the Diesel
Sound Simulator. In Fig.1, four
trackside sensors monitor the location of the loco and this information
is fed to the sound generator board
to produce a DC control voltage.
This voltage is then used to control
the volume of a single audio
amplifier.
By using this simple arrangement
the volume from the amplifier stage
fades (up or down) to one of four different levels as the loco passes
each pair of_ trackside sensors. In a
practical layout, you would arrange
for the sound level to increase as
the loco moves towards you and
then decrease as it moves away.
The two halves of the photo-interruptor are mounted on opposite sides of the
track. When the loco passes between them, it breaks the infrared light beam.
This causes the amplifier volume to increase for that sector.
But although this can produce
quite realistic effects, it cannot
change the apparent location of the
sound source, as the loco moves
around the layout. To simulate a
moving sound source, you need to
use the arrangement shown in
Fig.2. Once again, four trackside
sensors are used but each of these
now controls a separate audio
amplifier with its own loudspeaker.
In practice, it's simply a matter
of positioning the four loudspeakers
driven by the amplifiers to produce
DECEMBER1988
51
~
::c:
.....
z
n
0
t==:
.....
0
CJ':)
""NI
12VAC
.033
TRACK
VOLTAGE
.,.
IN
14
.,.
16 17
•
,.W- 100 .J,,t
•
10
16VW+ 16VW+
1our
•
~,t
K
LED
A
+12v
5.6k
0.27!
4.7k
.,.
+12v
f
.,.
1° l:w:I lli]
LOW FREQUENCY REPETITION
1
I INPUT
PARALLEUiJ!
SERIAL
l16
DIESEL SOUND GENERATOR
.,.
OUTrr--,,
IC2
4021
1.L..11LJTh
11 SERIAL
3 08
IN 3
COMP
I
10 CK
12 7
_III_H
470k
r------~~-...-.,_......,______
10 .WVR2
16VW"'I"!20k
THRESHOLD
'14
IC1 SIG !Nit'----
4046
vco
4.7k
+12V
GNU
~~
VIEWED FROM
BELOW
eQc
8
10kl
680k
8200
NOISE SOURCE
+12Y
0.1T
•
.039t
ALTERNATOR
SOURCE
470k
TRAIN
POSITION
SENSORS
+12V
.,.
o.1I
.,.
+12V
.,,
.,.
10~
l13
4
AMPLFIER
--0
AMPLIAER
3
.,.
+12V
.,,
02
03
AMPLIAER 3
04
AMPLIFIER
1.5k
,10
15
02
.,.
.,.
74C14,40106
:g
IC6
40175
IC4c/s\
?
112
03
-:
.,.
IC411J"s
t
113
04
0.1.;:
CLRl 1
680k
+12V
8!l
SPEAKER .,.
t6,,V~~
220
AMPLIAER 4
-:-
t t. 't ~
AMPLIAER 2
2.2 .J:
16VWJ
rJ:
16VWJ
220
12VAC
TRACK
l
l
SOUND GENERATOR
+12V
GND
SIGNAL
AMPLIFIER
1
TRAIN
POSmON
SENSORS
AMPLIFIER
2
AMPLIFIER
3
AMPLIFIER
4
1 2 3 4
+12V
+12V
TD LOUDSPEAKER TD LOUDSPEAKER TD LOUDSPEAKER
2
3
4
□
ed around the loop, from pin 11
through to pins 3 and 12, and via
the XOR gate (pins 14, 3 & 2 of ICl)
back to pin 11. Thus, IC2 and the
XOR gate in ICl generate a pseudo
random pulse train and the speed
at which this is generated is controlled by the VCO. This gives a
realistic "hunting" quality to the
diesel sound.
The output from the noise
generator is taken from the Q8 output of IC2 and applied to a low pass
filter consisting of a 4. 7k0 resistor
and 0.27µF capacitor. From there,
the signal is fed to the pin 5 input of
buffer amplifier IC3d.
White noise source
SENSOR
4
SPE:KER[J1
□
Fig.2: this alternative track layout uses four separate audio amplifiers and
four loudspeakers. The loudspeakers are mounted at appropriate locations
around the track to simulate a moving sound source.
the best effect as the loco moves
around the track. The volume from
each amplifier can be adjusted by
changing a single resistor value.
How it works
Most of the circuitry is contained
in eight low-cost ICs. Fig.3 shows
the details.
ICl and IC2 form a pseudorandom noise generator and
together provide the low frequency
exhaust beats so characteristic of a
diesel locomotive. ICl is a 4046
phase locked loop (PLL) and contains a voltage controlled oscillator
(VCO) and an exclusive-OR (XOR)
gate which is normally used as a
phase comparator. In our circuit
though, ICl is not used as a phaselocked loop. We are only using the
VCO and the XOR gate.
VRl, the 470k0 resistor and the
.033µF capacitor set the overall fre◄ Fig.3 (left): three separate noise
sources are used to simulate the
diesel sound. ICl & IC2 provide the
low frequency exhaust beats, IC3
provides the high frequency exhaust
noise, and IC3a & IC3b provide the
alternator whine.
quency range of the VCO, while its
actual frequency is set by the DC
control voltage applied to pin 9.
This control voltage is derived from
the track voltage via a bridge rectifier (D5-D8) and a voltage divider
consisting of two 4. 7k0 resistors.
In this manner, the speed of the
VCO is controlled by the throttle
setting on the train controller. The
higher the setting, the higher the
frequency of the VCO. When the
throttle is closed, the control
voltage on pin 9 is at a minimum
and the VCO runs at its minimum
value of around 300Hz, thus setting
the engine idle speed.
The VCO output appears at pin 4
of ICl and clocks IC2 which is a
4021 shift register. When the circuit is first switched on, pin 9 of IC2
is momentarily pulled high via a
0.lµF capacitor. This loads an 8-bit
number into the shift register (as
determined by the wired connections to pins 1, 4, 5, 6, 7, 13, 14 &
15).
Pseudo random pulses
The VCO signal is fed to pin 10 of
IC2 and thereby controls the speed
at which the 8-bit pattern is shuffl-
OK, so we have our low frequency exhaust beats. We now
have to simulate the high frequency
exhaust noise and this task is performed by transistor Ql and op
amp IC3c.
Ql is connected as a reverse
biased diode (ie, the base-emitter
junction is reverse biased) which
makes it into a good "white noise"
source. The resulting noise produced by Ql 's controlled avalanche
breakdown is AC-coupled via a
.047 µF capacitor to pin 10 of IC3c
which is a non-inverting amplifier
with a gain of 69. A voltage divider
consisting of two lM0 resistors sets
the bias at pin 10 of IC3c to half
supply.
The amplified output of IC3c appears at pin 8. From there, it is fed
via a l0k0 resistor to pin 5 of IC3d
where it is mixed with the low frequency exhaust beats.
Alternator whine
Unlike the previous two noise
generator circuits, the alternator
whine only comes into play when
the track voltage reaches a predetermined level. This provides
more realistic simulation, since
alternator whine only becomes apparent after a diesel loco gets up
speed.
IC3a and IC3b provide simulation
of the alternator whine. IC3a functions as an amplifier and controls
Schmitt trigger oscillator IC3b via
diode D9. Let's take a closer look at
how the circuit works.
Diodes D5-D8 provide full-wave
DECEMBER 1988
53
t-1- 12VAC
tTRACKt
®
HH ,rh~~~®
c~r-c
l
~
... ;~ 8 ®~®C¥;]'
1000uF
FL
12
+ v~O~R2
GNO_l...."
SIGNAL-
I
_
~
e
~
--mE}-l
[
~470
L~t2; ]
i
.l!;
:g
~
~ 09~
~
;!
i;j
liJ ~ ffi
~~
1
-!llliJ-
10k
--rrz:o..---cm::J-
.i: 8 I] -
--ruo,.
~
~~
I
~
<at>)
.,:e
!.1:;
..
®~
/'.!'\6 ~
.l!;
~ ~~
~
e - l3
CONTROL
I
TD AMPLIFIER 1
- - - - TO AMPLIFIER 4
..mo,.
A
oc VOLUME
1
- T D AMPLIAER 3
I
-TOAMPLIFIER2
~
1
K• E• K• E• K• E• K• Ee
~
~
A• C• A• C• A• C• A• Ce
OP1 __ OP2_ OP3_ OP4_ _ _ _ _ _ _ _ _ _ _ __.
Fig.4: here's how to mount the parts on the sound generator PCB. Make sure
that all parts are installed the right way around and use PC stakes to
terminate the external wiring connections. The 12VAC supply can be derived
from the train controller.
rectification of the track voltage as
previously described. The output of
this bridge rectifier is then fed to a
voltage divider, filtered by a lOµF
capacitor and applied to pin 3 of
IC3a. Trimpot VR2 sets the
threshold at which the circuit
begins to operate by applying a
preset voltage to pin 2.
So what does this all mean'? It
means that, at low throttle settings,
the voltage on pin 3 of IC3a will be
less than that on pin 2. Thus, the
output (pin 1] will be low and diode
D9 will be forward biased.
As the throttle is progressively
opened, the voltage on pin 3 rises
above the pin 2 threshold and IC3a
functions as an amplifier with a
gain of 2. When its output reaches
about 0.66 of the supply rail, D9
will be reverse biased.
D9 determines whether Schmitt
trigger oscillator IC3b functions or
not. The 470k0 feedback resistor
between pins 14 and 12 sets the
level of hysteresis, whilst a voltage
divider consisting of two more
470k0 resistors sets the midpoint
voltage on pin 12 to half supply (ie,
to + 6V).
54
SILICON CHIP
When D9 is reverse biased, IC3b
oscillates at about 2.4kHz, with the
.039µF capacitor alternately charging and discharging between
0.33Vcc and 0.66Vcc (ie, between
4V and BV). This signal simulates
the alternator whine and is fed to
pin 5 of IC3d via a 150k0 resistor
where it is mixed with the noise
signals from IC2 and IC3.
However, when D9 is forward
biased (ie, when the track voltage is
below the threshold level], the
voltage across the .039µF capacitor
is clamped to 0.5Vcc. As a result,
IC3b stops oscillating and the alternator whine ceases.
DC volume control
IC3d functions as a non-inverting
buffer amplifier and is used to drive
the following audio amplifier
stages. For the sake of clarity, our
circuit shows only one audio
amplifier. It consists of DC volume
control IC7, 741 op amp stage ICB,
and transistors Q6 and Q7.
If you want to add additional
amplifiers, all you have to do is
duplicate the circuit based on these
components.
IC7 is an MC3340P "electronic
attenuator" chip from Motorola. It
functions as a DC volume control.
As the voltage at pin 2 is increased
from 3V, the gain is reduced from
+ 13dB to below - 70dB at around
+5V.
In this circuit, a 470k0 resistor at
pin 2 sets the maximum attenuation
(ie, it sets the minimum volume from
the loudspeaker]. To increase the
volume when the train passes a set
of trackside sensors, all we have to
do is to switch another resistor in
parallel with the 470k0 resistor on
pin 2. This job is performed by transistors Q2-Q5 but more about that
later.
The output from the attenuator is
coupled directly to pin 3 of ICB,
which is a 741 op amp. This in turn
drives a push-pull transistor output
stage consisting of Q6 and Q7. From
there, the signal is AC-coupled via a
220µF capacitor to an BO loudspeaker.
Negative feedback for the
amplifier is via the 1.5k0 resistor
connected between the commoned
emitters of Q6 and Q7 and pin 2 of
ICB. Together with the associated
lkO resistor, this sets the overall
gain of the amplifier to 2.5. The
associated 2.2µF capacitor rolls off
the amplifier low frequency response below 70Hz.
Trackside sensors
Four photo-interrupters, OP10P4, are used as trackside sensors
to detect the position of the loco.
These photo-interrupters consist of
an infrared LED and an NPN Darlington phototransistor. Normally
used as position sensors in printers
for computers, they are cut in half
and the halves are located on opposite sides of the track (see Figs.1
& 2).
The infrared interrupter LEDs
are supplied with current via a
4700 resistor from the 12V supply.
The Darlington transistors have
their collectors connected to the
+ 12V supply and their emitters
connected to OV via 1 BOkO
resistors. When under full illumination from the LED, the phototransistor conducts and its emitter is
pulled high. When the light is interrupted the voltage at the emitter
drops to OV.
The four phototransistor outputs
This view shows how we mounted the sound generator PCB inside a standard plastic instrument case. Most readers
will probably prefer to mount the board out of sight, underneath the layout. The external wiring can be run using
rainbow cable.
are monitored by Schmitt triggers
IC4a to IC4d. The outputs of the
Schmitt triggers connect to the data
inputs of IC6, a 40175 quad D-type
flipflop, and to the inputs of quad
input NOR gate IC5, a 4002.
Data storage
IC6 is the key component in determining which amplifier's gain is increased. For the system to work
properly, the amplifier associated
with a particular sector of the
railroad layout must increase its
gain when the train enters that sector. At the same time, the amplifier
associated with the previous sector
where the loco was present must
fade down.
In addition, the circuit must be
able to cope with any change in
direction that the loco might make,
To simplify external connections, we terminated all the wires from the
generator board on two multi-way insulated terminal blocks. These are
recommended even if you don't use the plastic case.
DECEMBER1988
55
DC VOLUME
CONTROL
GNO
sa
SIGNAL
+12V
SPEAKER
Fig.5: parts layout for the DCcontrolled audio amplifier. The
+ 12V supply is derived from
the sound generator PCB.
Depending on your requirements, you can build up to four of these audio
amplifiers to go with the sound generator PCB. We mounted the amplifier in a
small plastic case but it could also be mounted in the same case as the sound
generator board or mounted under the layout.
For best sound output, the loudspeaker(s) used should have good bass
frequency response. If the high frequency response is excessive, you can chop
it back by reducing the 680kn feedback resistor between pins 8 & 9 of IC3.
as it enters, leaves and re-enters
any of the four sectors.
Whenever the loco passes between one of the trackside sensors,
the output of the associated Schmitt
trigger (in IC4) goes high. Normally,
unless the train stops light
transmission across one of the four
interrupters, all four Schmitt triggers will be low and the output of
the quad input NOR gate IC5 will be
high.
When one of the Schmitt trigger
56
SILICON CHIP
outputs does go high the output of
IC5 will go low. This low signal is
delayed by the 15k0 resistor and
0.1µ,F capacitor and then passed to
the input of Schmitt trigger IC4e.
The output of IC4e then goes high
and clocks the four D-type flipflops.
Let's say that the output of IC4b
has gone high. When IC4e goes
high, this high signal will be "latched" at the Q2 output of IC6, pin 7.
This will turn on transistor Q3
which will then pull down its callee-
tor resistor. This increases the gain
of amplifier 2.
If the loco then moves to interrupter OP3, IC4c's output will go
high, and IC6 will "latch" the high
signal through to pin 10. This will
turn on Q4 which will increase the
gain of amplifier 3. In the meantime, Q3 will have turned off and
the gain of amplifier 2 will have
been reduced.
The "CLR" (clear) input at pin 1
makes sure that IC6 is properly set
to zero from the start. At switch-on
the 0.1µ,F capacitor has the effect
of pulling pin 1 low which sets the Q
outputs (pins 2, 7, 10 and 15) low.
The 680k0 resistor then charges
the 0.1µ,F capacitor to +12V so
that pin 1 is high and IC6 can work
normally.
This means that until a loco
passes a photo interruptor, all
amplifiers will be at minimum
volume.
To control the gain of IC7 (or the
MC3340 associated with each
separate audio output stage), transistors Q2 to Q5 switch in a resistor
to ground. The 4.7k0 resistor at the
collector of Q2 sets the volume at
maximum, while the 15k0 resistor
at Q3 sets the volume at a minimum.
The 220µ,F capacitor on pin 2 of IC7
ensures that the gain changes are
not too abrupt.
If you want even slower fading
up and down of gain, increase this
capacitor further.
Power supply
Power for the circuit will normally be supplied from the low voltage
transformer which feeds the train
controller. Normally, this transformer will deliver between 12 and
20V AC. This is fed to the bridge
rectifier consisting of diodes Dl to
D4. The bridge feeds a 1000µF filter
capacitor and 7812 3-terminal
regulator to provide + 12V.
A l0µF capacitor at the output of
the 7812 regulator ensures its
stability. Another 100µF capacitor
across the supply but remote from
the regulator provides further
decoupling of the supply for the ICs.
Construction
The Diesel Sound Generator and
the amplifier are made up on
separate printed circuit boards.
These measure 117 x 130mm (code
SC09-1-0988-2) for the diesel
generator and 60 x 47mm (code
SC09-l-0988-1) for the amplifier
board. For a minimum set-up you
will need one generator board and
one amplifier board. For the most
complex set-up you will need one
generator board and four amplifier
boards, together with associated
loudspeakers.
Most readers will probably
prefer to mount the printed boards
beneath their track layout. However, both boards will fit inside
standard plastic cases, as shown in
the photos. The sound generator
board fits into an instrument case
measuring 200 x 158 x 68mm
(Altronics Cat. H-0480) while the
amplifier fits in a zippy case
measuring 83 x 54 x 28mm
(Altronics Cat. H-0101).
Assembly of the two PCBs is quite
straightforward just follow
Figs.4 & 5. Take care to correctly
connect the polarised components
such as the diodes, ICs, transistors,
the 3-terminal regulator, and the
electrolytic capacitors.
Testing
To simplify the connection of wiring, we terminated all the wires
from the generator board on two
multi-way insulated terminal strips.
For the initial test, do not connect
the DC volume control line(s) from
the generator board to the
amplifier. Instead, connect a 4. 7k0
PARTS LIST
Diesel Sound PCB
1 PCB, code SC09-1-0988-2,
117 x 130mm
1 plastic instrument case, 205
x 158 x 68mm (optional)
1 1 6-way insulated terminal
block
1 12-way insulated terminal
block
Semiconductors
1 40175, 7 4C175 quad D
flipflop
1 40106, 7 4C14 hex Schmitt
trigger
1 4046 phase lock loop
1 4021 8-stage static shift
register
1 4002 dual 4-input NOR gate
1 LM324 quad op amp
1 1 N914, 1 N4148 signal
diode
4 1 N4002 1 A diodes
1 7 81 2 3-terminal regulator
4 BC337 NPN transistors
1 BC548 NPN transistor
4 STIN3101 or equivalent
photo-coupled interrupters
Capacitors
1 1 000µF 25VW PC
electrolytic
1 1 00µF 16VW PC electrolytic
2 1 0µF 16VW PC electrolytic
1 0.27 µF metallised polyester
4 0 . 1µF metallised polyester
1 .04 7 µF metallised polyester
1 .039µF metallised polyester
1 .033µF metallised polyester
Resistors (0 .25W, 5%)
2 x 1 MO, 3 x 680k0, 6 x 470k0,
1 X 330k0, 4 X 180k0, 1 x
150k0, 2 x 15k0, 9 x 1 OkO, 1 x
6.8k0, 1 X 5.6k0, 4 X 4. 7k0, 1 X
8200, 4 X 4700, 1 X 200k0
miniature vertical trimpot, 1. x
20k0 miniature vertical trimpot
Audio Amplifier
1 plastic zippy box, 83 x 54 x
28mm
1 PCB, code SC09-1 -0988-1 ,
. 60 x 47mm
Semiconductors
1 MC3340P DC attenuator
1 741 op amp
1 BC337 NPN transistor
1 BC327 PNP transistor
Capacitors
3 220µF 16VW PC electrolytic
1 2.2µF 16VW PC electrolytic
1 1µF 16VW PC electrolytic
1 680pF ceramic
Resistors (0 .25W, 5%)
1 x 470k0, 1 x 1.5k0, 1 x 1 k0
Miscellaneous
Loudspeakers, hookup wire, tinned copper wire, solder etc.
The LED section of the photointerruptor has a small diode symbol
moulded into the plastic housing.
The photo-interruptor must be cut in
half and the two halves mounted on
opposite .sides of the track.
resistor between the DC volume
control input to the amplifier board
and the 0V line.
With all connections made,
switch on the power and check that
the 7812 regulator has + 12V at its
output. If all is operating correctly,
the diesel sound should be
emanating from the loudspeaker.
The pitch of the diesel sound should
increase as the train controller's
output is increased. You can set the
maximum pitch, to coincide with
the maximum throttle setting, using
VR1.
When setting VRl remember that
DECEMBER 1988
57
I
~
-~
~,
I
0
.
SC09-1-0988-2
L '7°1
l.
'7'7
58
SILICON CHIP
L.=
Fig.7: actual size artwork for
the amplifier PCB.
The actual volume level is dependent upon the resistor connected to
the DC volume control input. A
4. 7k0 resistor gives maximum
volume while a value of 15k0 gives
the minimum volume. The values
shown were used in our circuit but
can be altered to suit a different
track layout.
Options
Fig.6: here is an actual size artwork for the sound generator PCB. Ready
etched boards are available from the usual sources (see hack page).
the large diesels in locomotives
usually run at no more than about
1100 RPM when at full power. So
don't make it sound like a racing
car at flat-chat.
Adjust VR2 so that the hum cuts
in soon after the diesel sound
passes idle speed and as the loco
begins to move.
The remainder of the circuit can
now be tested by connecting up the
optical sensors and DC volume control lines to the amplifier(s).
The track sensor is made by cutting a STIN-3101 photo-interrupter
in half. We obtained our sensor
from Geoff Wood Electronics but
equivalents are readily available
elswhere. Alternatively, if you
wish, you can use a separate infrared LED (LD271, CQY89A) and
infrared photodiode (BPW50,
BP104R) or NPN phototransistor
(TIL81). The advantage of the interrupters is that they are easy to
...~.
mount and conceal as trackside
structures.
Cut the interrupter in half between the light emitting diode and
the phototransistor. Use a finebladed hacksaw for this purpose
and file the cut edges to provide a
smooth finish. The resulting
separate devices are mounted
directly opposite each other on
each side of the railway line. They
must be mounted on the same plane
and should be square on to ensure
maximum sensitivity.
Once the sensors are located and
wired to the PCB, the circuitry is
ready to be tested. When power is
first applied, the diesel sound
should be muted. For each interruption of a sensor, the volume should
adjust to another volume. When used with separate amplifiers, a different amplifier should operate for
each sensor and with a different
volume.
Besides the two optional set-ups
we have shown in Figs.1 and 2, a
number of other variations can be
added. For best sound output, the
loudspeaker should have a good
bass frequency response. If you are
using properly baffled speakers you
can obtain even better bass
response by modifying the amplifier
board. As it stands, the amplifier
circuit cuts off at about 120Hz. To
lower this to below 40Hz, increase
the 220µF output coupling capcitor
to 470µF, the 2.2µF feedback
capacitor to lOµF and the lµF input
capacitor to 2.2µF.
Note that this is only worth doing
if your speaker(s) have useable
bass response to 40Hz.
It is not necessary to use speakers with good high frequency
response. If you do so, you will probably find that the high frequency
noise output from the circuit is too
obtrusive. You can chop it back by
reducing the 680k0 resistor between pins 8 and 9 of IC3c. To make
a noticeable reduction, try a value
of 100k0.
~
Interesting circuit ideas which we have checked but not built and tested. Contributions from
readers are welcome and will be paid for at standard rates.
'------------
Charger for 12V gel
batteries
Standard 12V chargers intended
for car batteries should not be used
for charging 12V gel cells. They
charge at too high a rate and they
do not cease charging when the
recommended maximum battery
voltage is reached.
The circuit presented here limits
the charging current to 600
milliamps and cuts the current to a
low value when the battery reaches
full charge.
Power for the circuit comes from
a 2155 1A 15V transformer which
feeds four diodes in a bridge rectifier and a lOOOµF filter capacitor.
This produces a filtered but
unregulated supply of about 21 to
23 volts DC, depending on the
transformer.
This unregulated supply is then
fed to an LM317 adjustable
3-terminal regulator which functions to limit both the maximum output voltage and the maximum output current. Normally, when a battery is on charge, the circuit will be
acting as a current source. Then, as
the battery reaches full charge, it
A-/
240VAC
T
N
12V :
1000
25VW
E •
+
..L.
B
ELJc
VIEWED FROM
BELOW
OUT
Fig.1: when the voltage across the Hl resistor exceeds 0.6V,
Qt turns on and reduces the voltage across the 1.2k!l resistor and
2000 trimpot. This, in turn, reduces the voltage from the LM317.
will change over to maintain a constant voltage.
The circuit works as follows:
when the battery has reached full
charge, Ql and its associated base
and emitter resistors can be considered to be short-circuited. The
output voltage is therefore determined by the 1200, 1.2k0 and 2000
trimpot connected to the output of
the LM317. The 2000 trimpot is
there to set the output voltage to exactly 14.2 volts.
When the battery is on charge,
Constant current
nicad charger
Some of the cheap commercial
nicad chargers are little more
than a rectified AC power supply
with a series limiting resistor to
restri~t the current supplied to
the charging cells. While these
circuits do function as a charger
they do not provide an accurate
constant current to the cells,
especially if the number of cells
can be varied.
Consequently, it can be difficult to accurately time the
charging to ensure that the cells
are not over or under charged.
2155=----,
5V
the output current from the
regulator develops a voltage across
the rn resistor. If this voltage exceeds 0.6V, transistor Ql turns on
reduces the voltage across the
1.2k0 resistor and 2000 trimpot
and so reduces the voltage from the
regulator circuit as a whole.
In practice, the circuit settles at
a current of about 0.6A until the
battery is almost charged. As the
battery voltage reaches 14.2 volts,
the current through it drops to a
negligible value.
-
01
1N4002
50mA
12V
PLUG-PACK
1
.,..
Both cases can lead to a shorter
nicad cell life.
The circuit shown here is
designed to charge up to 6 AA
500mAh nicad cells in series using a precise constant current
source. The accuracy of the
charging current allows discharged cells to be completely
charged in 15 hours.
..
~
+
+
T
+
10
25VW+
NiCad
CELLS
I
...L..
OUT
An adjustable 3-terminal regulator (LM317) is the basis of the
circuit. Preceding the LM317 is a
diode and 470µF 25VW filter
capacitor. These components
enable the circuit to be fed with
a DC or AC plugpack.
If using a DC plugpack it can
be rated up to 18V while AC
continued on page 67
DECEMBER 1988
59
COMPLETE RANGE
MOTHERBOARDS
M B1600
M B2B6 120K
M B2B6 16 1M
MB2B61 6L1M
M B28620 1M
M B386202 ~l
10MHz XT M /Boa rd,OK RAM
Baby 286 M /Board, 12M Hz/0 K
Baby 286 M IBoard, 16M Hz/ 1M
Baby 286 M /Board, 16MHz/ 1m
Baby 286 M /Board, 20MHz/l M
Baby 386 M /Board,2 0MHz/2M
IC256K 12
IC256K 15
1(2 8710
IC2876
IC2878
IC64K12
IC64K15
IC8087
ICV20
ICV30
256 K RAM Chip - 120nS
256K RAM Chip - 150nS
PC Universal Card
EPROM Programmer
Card
Perfect for prototypi ng, with massive
4000 hole w orking area .
• Suits PC and AT systems
• Bui lt-in data bus, address bus 1/0 line
buffers
• Universal address decode chi p
• D-25 connector
$125
249 .00
64 5.00
1645 .00
1495 .00
1895.00
4 500 .00
CHIPS
80287. 10MHz Co-processor
8 0 287, 6MHz Co- processor
8 0 287, 8 MHz Co-processor
64K RAM Chip - 120nS
64K RAM Chip - 150nS
8087 -2. 8M Hz Co-Processor
NEC V20 Chip
NEC V30 Chip - 10MHz
23 00
19 .90
549 .00
3 15.00
450.00
9 .00
7 50
275.00
29 .00
49 .00
DISK DRIVES
DD 1037A
D01053
DD1157C
DD31 46 H
D05 126
DD5146 H
DDMCASE
$1,'141 0
SWCCSD
SW PAINT
SWSLl
SWSL2
SWSL3
SWWM
Disk Drive.NEC 720K,3.5in
Disk Drive, NE C 360K
Disk Drive, NE C 1 2MB
Hard DD, NE C 40MB, 35mS
Ha rd Disk Drive, NEC 20MB
Hard Disk Drive, NEC 4 0MB
S.25 in case - 3.Sin drive
23 5 00
225 .00
245 00
855 .00
495 .00
895 .00
25 .00
SOFTWARE
MS DOS V3 .2 - (NEC)
CCS Designer
CCS Pa1n tshow
CCS Symbol Li bra ry No 1
CCS Symbol Library No 2
CCS Symbol l ibra ry No 3
Wordmag1c, Wordprocessmg
80.00
179 .00
55 .00
79 00
79 00
79 00
139.00
This superb EPROM burner comes wit h a
high quality ZIF socket and cabling
Facilities include the ability to read, write,
copy, compare and erase the contents of
EPROMs.
Compatible EPROMS include: 2716, 2732,
2764, 27128, 27256, 27512, 2804, 2816,
2864, 58064. It comes complete w ith
software and user manual.
$245
~
AD-DA Conversion Cards
■
■
Input/Output voltage 0-9V (adjustable)
u1,ipolar or bipolar
215 .00
s
ACCESSORIES
AC2MP
AC3 M P
AC5400
ACDA
ACOM
AC LA
Prin ter Ca ble, 2M , 2 5 pin
Prin ter Ca ble, 3M, 2 5 pin
14 EGA Colour Monitor
ACM2
AC M A
ACMG
9 pin Designer Adaptor
Des19ner Mouse (2 90 DPH
25 pin Logitech Adaptor
Log1tech Mouse
NEC Mult1sync II Monitor
Monitor TTL Amber
Monitor TTL Green
PR2200
PR22CSF
PR30
PR760
PR7BT
NEC P2200 Pri nter
Cut Sheet Feeder P2200
Printer. Olympia 9 pm
NEC P7 Printer
NEC P7 B1-d 1rect1onal Tr
AC LM
12 00
15 00
745 00
10.00
99 00
1000
149 .00
1249 00
199 00
199 00
PRINTERS
695 .00
155 00
425 00
1355 00
226 00
CONSUMABLES
COD360
CODB360
COMD720
Diskette. box of 1O, 360K
Diske tte. 360K. Bulk Pack
'V1 1cro Disk.Box of 10,720K
10 1005
10 1009
10 1010
1010102P
101014
1022 1G
102230
102250
IOCH IP
Multi I O Card XT on!y
Para liel Printer Ca rd
Serial RS232 Card.XT on ly
Seria l P.S232 X ?.. XT only
I O Plus Card XT Only
Serial Parallel Card XT
I O Plus Card AT only
Mull! 110, 25, 1P. 1G, AT
Chip Set for IC1010
vc 1623
vc 1625
Turbo Colour Graphics Cd
Colour Graph,cstMono Ca rd
ttiA Card, W 1Hercules Mode
Turbo Mono Graphics Card
Tu rbo/Mono Printer Card
20 00
2 50
66 00
1/0 CARDS
11', uo
4 a oo
'>5 00
00
79
136
125
245
399
25
00
00
00
00
00
VIDEO CARDS
VC 1629L
VC1613
vc 1635
165 00
195 00
249 00
165 00
175 00
DISK CONTROLLER CARDS
DC 1004A
DC 1220
DC2 200
DC22 10
DC2300
DC23 10
DC2 340
Floppy Disk Ca rd, 4 Ports
I 2Ml 360K.720K 11 44M FDC
Hard Disk Controller XT
HDDIFDD ConU Board XT
Hard Disk Controller AT
HOO/FOO Controller AT
LHDD14DD Controller AT
65 00
145 00
145 00
199 00
245 00
295 00
355 00
POWER SUPPLIES
PS9150S
PS9 180
PS9180L
PS9200
;~g: ~::~~~
1
~~JSUBab~TAl
180W PSU. Baby AT. L Type
220W Switching PSU AT
148
170
170
220
00
00
00
00
KEYBOARDS
KB101
KB84
Keyboard, 10 1 Keys XTIAT
Keyboard, 84 Keys XT 1AT
CAAT
CAATB
CAXT
Case, hinged AT
Case Baby AT, hinged
Case . hinged XT
14 5 00
125 00
CASES
155 00
135.00
95 00
INTERFACE CARDS
IF04 5
IF04 6
IF054
IF0 55
IF 1638
IF286S
IF488
IFADDA1 2
IFADDA14
IFEPROM
IFTEGA
Seria l RS-42 2 Adaptor
Indust rial 1/0 Card
Universal Wire-wrap Card
Dual Sena] RS -422 Card
Facs1 m1te Card
80286 Speed-up Card
IEEE 488 Interface Card
A-0/0 -A Conv. 1 Channel
A-0 /0 -A Conv, 2 Channel
EPROf\,-1 Wn ter Card
Orchid Turbo EGA Card
RCt015
RC2000
RC23SO
Universal RAM Card.OK RAM
2MB EMS Memory Cd, OK RAM
3.SMB M/Funct Cd OK RAM
135 .00
445 .00
125 .00
195 .00
1249 00
595 .00
465 .00
2 15 .00
599 .00
245.00
950 .00
RAM CARDS
' OK RAM MEAN\ ZERO RAM FITTE D.
99 00
295 00
495 .00
Powerful CAD Package
s299 inc. mouse - blimey!!
N
ow yo u can create deta iled ,
professional qua lity designs and
drawings quickly, easily and
inexpensively.
CCS Designer comes w ith many of the
same powerf ul featu res fou nd in CAD
systems costing thousands of dollars. All you
need is an IBM PC/XT/AT or compatible
co mputer w ith 512K RAM . You'll be creating
designs in under 30 mi nutes.
Use it for dozens of applications :
Architectu ral designs, organisational charts,
mechanical designs, business graphics,
electronic circu it layouts, interior designs,
landscapi ng, flow charts, floor plans. Built in
drive rs support 180 mice, 52 inp ut devices,
77 plotte rs, math co-processors and most
display card s. An optional utility allows
conve rsion to and from AutoCAD f ile format
so you can excha nge fi les wi th AutoCAD and
read CCS Desi gner draw ings into Desktop
Publishing programs.
CCS Designer produces high qual ity output
on matrix and laser printers - you don't need
an expensive plotter for good resu lts .
Use CCS Designer w ith our Symbol Libraries.
Symbol Library Volume One:
Electri cal , Electronic and Plumbi ng symbols .
Symbol Library Volume Two:
Home design an d home f urn ishing symbols
for creat in g floor plans and interi ors .
Symbol Library Volume Three:
Flow chart sym bols for drawing professional
quality flow charts.
F
EATURES
• Enlarge • Rot at e • Zoom in and out
• Pa int/fill • Undo • Redo • Flip
• Move, copy, delete and save sections • Plot
to a dot matrix pri nter • Arcs and curves
• Adjustable grid an d snap gravity point
• M ultipl e charact er sets • 8 line types w ith
adjustable th icknesses • Clearly w ritten
man ual and on-line help • Create your own
symbol libraries • Retrieve symbols at any
size, angle, or locat ion • 16 colour high
resolution display and output • Auto
dimensioning and scaling • Si ngle keystroke
comm ands • Point XY comm and • Point
Polar command • Repeat copy section
• Gravity move • Ortho line • St atic zoom
CCS Designer and DEXXA Mouse
$299.00
Symbol Libraries
.... ... $79.00 each
SPECIAL OFFER
At Last! A High
Qua lity Mouse you
can afford!
Elect ronic Solutions have tra cked down a
very hig h performa nce, indu st ry stan da rd
mouse . At $99 , it co sts aro und one th ird
the price of lower performance rod ents .
The mouse is a convenient seri al t ype and
co mes with sof tware to te st, set up and
operate .
A major improvement over other mice
w ith the Electron ic Solution s mouse is
higher reso lut ion and hi gher tracking
speed - up to 600mm /sec.
Features which set it above other
mice include:
• Extra high resolut ion: 290 DPI and up
• Sel ect able baud rate 1200, 2400,
4800 , 9600
• Optimum mecha nism: Ba ll on centre
• Super t racking speed : 600mm /sec and
up.
The ES Mouse is compatible wi th
appli catio n sof tware supporting
Microsoft and Mouse Systems mice. This
incl udes AutoCAD, ClickArt, Desqview ,
Dr. Ha lo, GEM, Microsoft Window s,
BABY SIZE PC/AT MOTHERBOARDS WITH
SPEEDS UP TO 20MHz - WOW!!
Specif ications:
Cat. No.
Pri ce
CPU (CMOS Version )
Clock Rate
Chip Set, C&T NEAT
On-Board Memory
RAM Speed
1/0 Slots Speed
Co-processor
BIOS
Keyboard Cont roller
Power Good Generator
OMA
Interrupt
Rea l Time Clock
Timers
Battery
Board size
Mounting Holes
MB 2861 20K
$645 .00
80286-10MHz
1211018MHz
MB28616L 1M
M B286 161M
MB 286201M
$1495 .00
$1645 .00
$189 5.00
80286-12MHz
80286- 16MHz
80286 · 16MHz
16, 12 1018MHz
16 12: 10/8M Hz
20 16, 12 10 •8M Hz
(Jumper, keyboard & software selectable)
10 MHz
12MHz
16M Hz
16Mhz
OK RAM fitted
1M byte fitted
1M byte fitted
1M byte fitted
exp . to 2M byte
exp . to 4M byte
exp. to 4M byte
l 20nS (OIL type)
l 20nS (SIMM type) 120nS (SIMM type) 1OOnS (OIL type)
1211018MHz
20 1612 108Mh
16i l2 10i8Mhz
16 12 10 8Mhz
Software selectable w ith programmable wait state to su it add-on cards of
different speeds
Optional 80287 (6,8, 10, l 2Mhz selectable by DIP switch)
Award BIOS with built-in setup (i ncluding CMOS & extended CMOS)
Award version 1.3 or above
On-boa rd Power-good generator,
Jumper selectable
7 channels
16 level interupts
Bu ilt in
3 programmable timers
Off board long life
battery included
85'' w ide x 13" long
2 sets - PC/XT, Min i/baby AT Standard Size AT
EGAcardunmatched resolution
Get all the standards with this superb short
slot EGA card .
■ Supports 132 columns in Symphony,
Lotus and WordPerfect
■ Automatic monitor
detection
■ 256K of video memory
standard
■ Flicker free scrolling
w
lii1;-Q
•I
j_"~_-.-:: ~
fJ
!
-.
w
•
.
(~
;f
f:
.;~w-..,>• ''... ..-*,..B.....
I,
I
$99.00,nc.tax
9 pin to 25 pin adaptor, suit AT computers
only $10.00
Dealer enquiries welcome
IEEE 488 Adaptor
(GPIB interface)
Industry standard inst rlJ.f!l_entatio n
interface.
• Su its both PC and AT systems
• Standard IEE E interface
$ 465
• 250K-1 M byte
t ransfer rate
• Manages up to
15 devices
• Basi c language
dri ver
included
P.O. Box 426 Gladesville 2111
Phone (02) 427 4422
We accept: Bankcard, Mastercard and
Visa. Mail orders our speciality. All
prices include sales tax.
Note: Products may vary in
appearance from those pictured . In all
cases they wi ll perform to the same, or
better standard .
■ Supports Monoch ro me, Hercu les,
CGA, and EGA modes. Fu lly auto
switchable
-/
Microsoft Word, Norton Utilities,
PageMaker, PC Pa intbrush, Persona l
Edit or, Smartwork, TopVi ew , Ventura
Publisher and many thousands more.
The mouse includes its ow n pocket and
pad. Introductory price is on ly
C
• All products carry a 14 day money
back guarantee
■ All products carry a fu ll 3 months
warranty
■ All cards come with full documentation
■ Ring for quantity discounts and tax
free prices.
■ Freight $7.50 forfirst item, then $2 .50
for each extra item.
Dealer Enquiries Welcome
The customer has no idea
I often wonder whether the customer ever has the
slightest inkling of what a serviceman goes through
in tracking down some of Murphy's most vicious
creations. But even as I ponder, I know the answer:
the customer's thinking is light years away, across
a chasm that can never be bridged.
And what brought on that little
burst of philosophy? Answer - one
of the most frustrating and least
satisfying exercises I have experienced for a long time. It included just about every negative aspect
one could imagine.
Quite apart from the technical
problems, there were difficult
customer relations. These involved,
among other things, a reluctance to
reveal the set's previous history
and a threat to bring consumer affairs into the situation. And I need
hardly add that the whole exercise
was a complete dead loss financially.
The job started out routinely
enough; a phone call from a new
customer enquiring as to whether I
could service her TV set. When I
said I would be happy to do so, she
said it was a Sanyo colour set
which had stopped dead in the middle of a program. Since there didn't
seem to be much point in probing
deeper right then, I simply suggested she bring the set in to the
shop.
When she turned up a couple of
days later the set turned out to be a
Sanyo model CPT 6603, which first
appeared about eight years ago. A
quick check confirmed that it was
quite dead. I made some attempt to
delve into the set's history but the
customer seemed strangely ignorant in this regard. But I also
sensed that she didn't like being
questioned.
When I opened the set the first
thing I found was a blown mains
fuse, a 2A slow-blow type. Based on
experience, I mentally nominated
three possibilities: a faulty degauss
thermistor, a faulty horizontal output transistor, or a faulty switching
transistor in the power supply. Of
these, the last named was the most
common.
The power supply board mounts
vertically on the left hand side of
the chassis (from the back) supported by a metal frame. Releasing
a screw on the main chassis frees
the frame and allows it to be swung
to one side. The power supply
board can then be freed from the
frame, giving access to the copper
side.
The switching transistor, Q361
(2SC1046L), is mounted on this
board on a fairly substantial
aluminium heatsink, about 50mm
square. This, in turn, is mounted
clear of the board by small spacers
but is still close enough to allow the
base and emitter pins of the transistor to pass through the board to
the copper tracks.
Knife & blow lamp
~t1<~
,... .:SU,- 1: AL.~ SE.NSEO SHE.
DION~ L-lKE. ge.1N6 qUE~TID~Et>...
62
SILICON CHIP
It was as I swung the board clear
that I received my first surprise;
something which, with hindsight,
should have warned me that trouble lay ahead. One glance told me
that someone had been there before
me. And unless I was very much
mistaken, he had been wearing a
striped apron and had attacked the
board with a butcher's knife and
blow lamp.
Well, you know what I mean. It
was a mess. Excessive soldering
heat had destroyed the original cop-
. ~Well, to cut it short, it was the
same situation as before; a blown
fuse, a shot switching transistor,
and a couple of faulty diodes. But
why? I would have liked to have
blamed coincidence but deep down
I knew this was clutching at straws.
There just had to be a more fundamental reason.
I went through the motions of
replacing all the components and
soon had the set running again. But
there was no way that I could
return it with the threat of another
failure hanging over it. At the very
least I owed the customer an explanation for whatever time it was
going to take to find the real fault.
So I rang the number and this
time found myself talking to the
lady's husband. And, after giving
him a brief resume of the situation,
I found him to .be as outgoing as his
wife was taciturn. I learned that
the set had already failed in a
similar fashion on three occasions,
and had been repaired by another
serviceman, whom he named.
Well, that explained a lot of
things. I knew the serviceman he
mentioned and realised that I
erence is the 2S0380 which has the should have recognised his hanhighest ratings of the lot.
diwork. He is reasonably clued up
I took the precaution of making technically but is sadly lacking the
the first test at a reduced voltage skills necessary to handle today's
via the Variac, increasing the components.
But it explained more that that.
voltage gradually in case there was
anything else amiss. But everything The fault was obviously a "stinker"
went smoothly and I soon had the that had already defied three efset running at normal voltage.
forts by the other serviceman until,
I ran it for several hours that apparently, the customer became
day, spent some time the next day fed up with the situation and sought
cleaning up the butchery as best I out someone else - Yours Truly.
could, then ran it for a couple more None of this did anything to cheer
hours. Then I rang the customer meup.
(I learned later of a further comand told her it was ready. She called in later, paid the bill - it was plication. The husband and the seraround $70 - and collected the set. viceman were golfing buddies. One
can imagine the conflict that situaAnd that was another one down.
tion created in the husband's mind.
It's not that simple
And what of the domestic situation?
Oh yeah! I wouldn't be writing While I sensed a lack of agreement,
this had it been that simple. A cou- I couldn't decide whether he was a
ple of weeks passed and then the henpecked husband or she a
roosterpecked wife).
lady was on the phone with the
complaint that the set had failed
But right then I had to content
again and, according to her, it was myself with pointing out, as
the same fault as before. I was well diplomatically as possible, that he
aware of the significance of that might have saved a lot of time and
remark but I wasn't going to argue
trouble - and money - if I had
at that stage. I simply invited her to
known the set's history in the first
bring the set in again.
place. And I added that it might
_ _._,
per tracks to the transistor pins and
these had been replaced with short
lengths of heavy scrap wire, clumsily soldered into place. And I could
see that several other components
had been removed for testing or
replacement. There was no damage
here but one could see where he'd
been.
I made a mental note to clean
things up later. I didn't want
anyone seeing that mess after I hq.d
handled the set.
But first I had to fix the fault. It
took only a moment to confirm that I
had picked it in one; Q361 was a
dead short between collector, base
and emitter. This type of failure is
not unknown in this model and I had
seen it often enough before to know
that any one of three diodes D362, D363 and D364 - could also
have been destroyed (sometimes all
three). In this case it was D362 and
D364.
Repairs were simple - fit two
new diodes and a new switching
transistor. In place of the
2SC1046L I use a 2S0350 or a
2S0380. Both have higher ratings
than the 2SC1046L and my pref-
DECEMBER1988
63
SERVICEMAN'S LOG
take some time to find the real fault.
Fortunately, they had a spare set.
Circuit checks
So it was back to the bench. I connected the CRO to the switching
transistor collector, hoping I might
detect some abnormality to account
for what it now transpired were
five transistor failures in a few
weeks. Unfortunately, this only
revealed that the waveform was a
copybook version of that shown on
the circuit.
At this stage, I suspected that
something might be generating the
odd spike or spikes but, unless I
was very lucky, I wouldn't be watching when they occurred.
In the light of this there was little
I could do except let the set run and
hope that when it failed again - as
I felt sure it would - it would provide some clue. In fact, the set ran
for several days with no signs of
trouble. Then, one afternoon, I left
· the workshop for a few minutes and
returned to find it dead.
I pulled the faulty transistor out,
found a couple of the diodes which
had gone with it, and replaced
these as a matter of course. But
there seemed little point in simply
64
SILICON CHIP
fitting another transistor and
waiting for it to fail in a few days. I
had to make some effort to find the
cause.
More in desperation than anything else I decided to examine the
heatsink mounting and the associated connections to the board, in
case an intermittent connection
might be generating spikes. So I unbolted it from the board and
carefully inspected the mechanical
assembly. I drew a complete blank;
there was nothing to arouse the
slightest suspicion.
But the exercise did prompt
another thought; what about the
mica insulating washer between
the transistor and the heatsink?
The best view of it in situ revealed
nothing so I pulled it out for a closer
look through a jeweller's loupe. And
there it was; what I had mistaken
for a tiny spot of discolouration which often occurs in mica - was
in fact a pinhole. It was so small
that I doubt that more than the
point of a pin would have passed
through it.
Well, we seemed to be getting
somewhere at last. I fished out a
new washer, examined it under the
glass just to make sure, then fitted
everything back together. The set
came good immediately and I settled down for another soak test.
Another splat
It was a brief test. The set hadn't
run for more than a couple of hours
when there was a sudden "splat"
and it went dead. My heart sank:
not only had I not fixed the fault but
I had probably done in another
transistor. And these are not the
10-cent variety- they run closer to
$10, even at trade prices.
Closer examination brought some
consolation; the mains fuse had
blown, but the transistor and
diodes were still intact. What was
more, there was a clear mark
where the flashover had occurred;
from the transistor case (collector)
to the heatsink, across the edge of
the mica washer. And it was then
that I realised that the new washer
was smaller than the one it had
replaced.
Both were nominal TO3 washers
but the original had been a good
5mm larger all round than the transistor case, while the replacement
was a neat fit. I must confess that I
was somewhat puzzled by this turn
of events. Was the design so critical
that only an oversize washer would
withstand the normal voltages in
this part of the circuit?
There seemed to be only one way
to find out; fit an oversize washer
and try again. After some searching
I found one; larger in fact than the
original, being close to 8mm larger
all round. So this was duly fitted
and, muttering something along the
lines of "Beat that, you b ... ", I switched on again. And again the set
came up and played normally.
For a couple of hours. Then there
was another splat and this time it
took out the transistor, plus one of
the diodes. And again the weak spot
was evident; the bolt holes in the
washer were marginally larger
than the previous ones and this was
where it had flashed over.
I was feeling pretty desperate
·1:
·ER..
UNIT
I
I
'
C:307
RJO<
560 K
c:i ,o
CJII
'"""' '"""'
TC~'l9
'305
560K
,.,
i
t C387
100., F
.
,
,,,'~
m
-!-
POWER-SUPPLY UNIT
':' ') OEFLl:"CTI ON
Fig.1: the power supply circuit for the Sanyo Model CPT 6603 receiver. An obscure and frustrating fault caused
repeated failure of the main switching transistor, Q361.
and disheartened by now, but there
seemed to be nothing for it but to
heed the obvious lesson and try
again. After a lot of searching I
found a large washer with small
holes, put everything back together
and tried again.
This time things looked a lot more
promising. The set played for
several days, during which time the
lady customer was on the phone
showing obvious signs of impatience. I explained that, hopefully,
the fault had been fixed but that I
wanted to run the set for a couple
more days, just to be sure.
Somewhat grudgingly, she accepted
my explanation.
So I ran the set for a few more
days and then, with no hint of trouble, rang the lady and told her she
could collect the set. And I did explain that I was making an additional charge - about $30 - purely to cover material costs - ie, the
transistors. I would not have dared
to try to charge for my time. She
seemed to accept this and duly collected the set and paid the bill. I
heaved a sigh of relief as the set
went out the door.
An irate customer
It was a misplaced gesture. The
set had been gone only three days
before the lady was on the phone
with the news that it had failed
again. And, understandably, she
was pretty irate. For that I could
hardly blame her. From where she
stood she had spent a lot of money
(including whatever the other serviceman had charged), experienced
a lot of inconvenience, and seemed
to be getting nowhere.
But what upset me was her
threat to take the matter to consumer affairs; in fact, she intimated
that she had already contacted
them. Assuming that this was not
just bluff, and knowing consumer
affairs, I imagine that she would
have been advised to take the matter back to me, then contact them
again if I refused to co-operate.
Since I had never had any such
intention I wasn't particularly worried about the threat but I was an-
noyed. I felt that she might at least
have consulted me first. And I spelt
this out, adding that I was perfectly
willing to stick with the problem, at
no additional cost, until it was solved. She calmed down a little after
that and agreed to bring the set in
again.
Naturally it was exactly the same
fault, except that there was no
evidence of a flashover from transistor to frame. I'd beaten that but
it was now clear that this was only
a symptom. And it was also clear
that I needed help. So I rang the
Sanyo service department and
eventually contacted a technician
who seemed to be familiar with the
fault.
We had a long discussion and out
of it came a list of components
which experience had shown were
likely suspects. These were: C361
(2200pF) in series with R361 between emitter and collector of Q361;
diode D361; capacitors C332 (22µF)
and C351 (220µF), connected to terminal 13 of the converter transformer (T361); and the main filter
DECEMBER1988
65
Problems?
.
SERVICEMAN'S LOG
'
..
' . . •:
... and you
don't have our
I20page
catalogue . ..
.... ..
I-\£~,
~INK
At last . ..
a TRADE
catalogue for
the consumer
ARISTA ... your one-stop problem
solver. Video plugs and sockets .. .
Video extension speakers .. . Video
flyleads . .. Video RF interference
filters .. . Video splitters .. . Indoor
antennas . . . Video switching units
. . . Down converters . . . Video
speaker controllers . . . Video
camera lights . .. Video tape
rewinders ... Video cine adaptors
. . . Video head cleaners . . . Video
splicing kits ... Video storage
cases . . . Video dust covers . . .
Video leads . . . Scart plug leads
. . . Video dubbing kits . . . Video
headphones . . . Video shotgun and
wireless microphone systems .. .
Pre-amplifiers with video inputs .. .
Video camera stands . ..
Just about anything
you want.
. . . Try us ... NOW!
Get your catalogue FREE
from your local ARISTA
dealer or send $2.50 P&H
and your return address to:
ARISTI\.
ELECTRONICS PTY LTD
PO BOX 191, LIDCOMBE, NSW 2141
66
SILICON CHIP
W~'S\½ER
M\CA
~£'RE. WAS A G~~~ MARK ~~E 1ME:
FLASHOVE."R \.\AD CXCOR~E.'t); FROM -rME
-r'R.AN~\S"f"OR CASE. 1'0
"ffie. HEP«'SINK,
AGRO~S 1'\E. E-'PGE 0~ 'THE MICA WAS\-\~,, ...
capacitors, C310 and C311, both
100µF.
But he'd kept the best bit until
last. A prime suspect was the trigger transistor, Q321. This should be
replaced as a matter of course,
along with any othe~_r of the
aforementioned components which
tested less that 100% or were
doubtful for any reason. I thanked
him very much and then, as he
wished me luck, he joked; "If that
doesn't fix it, - you're on your
own."
A comforting thought!
But at least I now had a few leads
to follow. I started with C361 and
D361. Both checked OK but I
replaced them anyway; after all, if
a minor component has to be pulled
out to be tested, it is just as easy to
fit a new one in its place .
When I came to capacitors C332
and 351 it was obvious that these
had been replaced by the previous
serviceman. Not only were they
brand new but, for once, I was
grateful for his style of soldering; at
least I knew what he had tried.
Similarly, the main smoothing
capacitors, C310 and 311, had obviously been removed, though I
couldn't be sure they'd been replac-
ed. So I pulled them out and checked them. They both tested OK, well
on the plus side in fact, so I refitted
them.
That left only the trigger transistor, Q321. Since my predecessor
seemed to have been following the
same path, I wondered whether he
had received the same advice and
had replaced this also. If he had,
we were back to square one.
Fortunately one glance at the
board reassured me. There was no
way that Butcher Bill could have
removed that transistor and put it
back the way it was. So out it came
and in went a replacement. Then I
fitted yet another switching transistor, put everything back together, and switched on again.
It was no surprise when the set
came up with perfect picture and
sound; that had happened many
times before. The real test was
whether it would last.
I ran the set every day and all
day for the next fortnight and it
never missed a beat. But as vital as
this test was, I couldn't convince
the customer of that. In spite of the
fact that they had a spare set, she
was on the phone every couple of
days wanting to know when it
TETIA TV TIPS
Kriesler 59-4/5/6
Telecommander Remote Control
Symptom: At switch on will select
channel 6 sound only at low
volume. No picture . When any
channel button is pressed, sound
increases to normal but still no sign
of picture .
Cure: IC1320 {TDB1030) faulty.
Although IC1380 does the channel selection , it is IC1320 that
does the actual switching and a
fault in this chip cuts off the tuning
voltage.
would be ready. And no amount of
explanation on my part seemed to
penetrate.
But at the end of a fortnight I
reckoned that the point had been
proved, at least to the extent that it
could ever be proved, and I returned the set to her. I made no charge
and urged her to contact me if there
was further trouble. This was accepted with moderate grace but
without any enthusiasm.
Well, that really is the end of the
story, except that several months
have now passed and I have checked the situation several times during that period. And each time I
have been assured that all is well.
So it would seem that Q321 was the
real culprit.
Of course it's easy to be wise
after the event but it is now obvious
that the flashovers around the transistor were merely symptoms of the
fault that was generating destructive spikes. The fact that I fitted
washers marginally different from
the original simply served to produce a nice red herring; one which
cost me dearly.
So why did Q321 generate those
spikes? I haven't a clue - and
neither, it would seem, does Sanyo.
Suffice it to say that it is a well
documented fault and one worth
noting. Perhaps this story may save
someone else the run around.
Another mystery
And while we are talking about
mysteries, here is another one to
mull over. It is about a brand new
National colour TV set, model
AW A Thorn 3500 Series
Symptom: Very low, wedge
shaped picture with very bad convergence. All voltages normal and
vertical output waveforms also normal. Looks very much like shorted
turns in the yoke.
Cure: Break in track on convergence board, between Plug 25
Pin 6, and L7 54. This track
passes close to one end of R751,
a known source of dry joints and
the break was at the closest point
to the resistor.
TC2959, only recently released.
This is a most impressive set,
featuring a 74cm (29in) screen, a
frighteningly elaborate remote control system, and a price tag of about
$2000 to match. It also boasts the
best picture resolution that I have
ever seen on a colour set.
Shortly after its release the
makers issued a modification sheet
concerning a corner purity problem. This was due to insufficient
degaussing current due, in turn, to
the type of degaussing thermistor
originally fitted. It recommended
fitting an alternative type, Part No.
ERPF5BOM12OG.
I have modified a few of these
sets and the modification works
well, even without any external
degaussing. So I wasn't worried
when one of my regular customers
phoned to say that they were having trouble with this model set, the
customer's description of the fault
being that " ... the colour's gone all
funny".
She explained that the set had
been working fine when they had
gone away for the weekend but had
"gone funny" when switched on
after they returned. I imagined that
it was just another modification job.
In fact it turned out to be one of the
worst purity problems I have ever
seen; the whole screen was a bright
random pattern involving every colour of the rainbow. There was no
way that this was the problem I had
anticipated.
Nevertheless, I went through the
motions of checking the thermistor,
confirmed that it was the old type,
Circuit Notebook ...
continued from page 59
plugpacks up to 15VAC are
suitable. Either way, the source
should be able to supply about
50mA or more.
The circuit operation relies on
the fact that the LM317 maintains 1.25V (nominally) between
its adjust terminal and the output
terminal. By connecting a
resistor between these terminals
it can thereby be made to function as a precise constant current source which is independent
of input voltage or load voltage.
Two resistors in series, 22n
and 2.20, set the constant current at close to 50 milliamps (actually 51.6 for a regulator
voltage of 1.25V}. Up to six cells
in series can be charged. Charging time is 14 hours (unless otherwise specified).
If you have 400mAh AA cells
they should be charged for 14
hours at 40mA. To set the ch.arging charging current at 40mA,
change the 2.20 to 8.20.
116
TV TECHNICIANS &
SERVICE COMPANIES
Have your
PHILIPS V ARICAP
TUNERS (ELC2060)
Repaired or Exchanged
Only $17 .00 ea.
Ten or more $15.00 ea.
Quick Service
3 Months Warrc1nty
T.V. Test Equipment
Shorted Turns Tester
(Silicon Chip, Sept. 88)
$65.00 ·+ Tax
Hi-Voltage Probe
0 · 50kV.
$70.00 + Tax
Send Faulty Tuners
Cheques and money orders
+ P&P $2.00 or C.O.D.
-:r.v.Tu
IIERs)
216 Canterbury Road,
Revesby 2212, Sydney Australia
Phone: {02) 77 4 1154
DECEMBER 1988
67
presto! - the problem vanished; I
had a first class picture with as
high a degree of purity as I have
ever seen.
So what was going on? My first
reaction was that there had to be
some factor in the customer's home
which I had overlooked, such as
audio speakers which might have
been moved close to the TV set. But
even that assumption posed as
many questions as it answered.
In order to change the thermistor, I had pulled the set into the
centre of the room, where it was
quite clear of any other objects. So
why, in that situation, had my
degaussing wand lost its magic?
Spurious magnetism
and fitted a new one. All of which
had no effect whatever on the problem. This didn't surprise me and I
simply reached for the degaussing
wand and gave the front of the set a
once over lightly.
But that didn't help either. When
I switched the set on again the ef~
feet was as bad as ever, although I
did get the impression that the actual pattern had changed. So I tried
again, being more careful this time
and since the back was still off the
cabinet, I went right over the inside, poking the wand in wherever
it would go.
Still no joy. I went through the
ritual several times but seemed
unable to make any impression. The
only noticable effect was that, if I
left the set running, I could observe
a changing pattern but with no hint
of reduction.
Faulty picture tube
That really rocked me. There
was only one possible explanation
in my experience and that was a
faulty picture tube. The fault is
rare but I have experienced it. It is
caused by a faulty spot weld securing one corner of the shadow mask,
allowing the mask to move back and
forth and upset the critical adjustment of the whole system. And a
68
SILICON CHIP
symptom is that any attempt to
degauss the set simply changes the
pattern.
It was also a situation which called for some diplomacy. The people
involved were very understanding
types but I hesitated to suggest that
their brand new $2000 set had a
faulty picture tube. While it would
be fixed under warranty, they'd
probably worry about a picture
tube failure for years to come!
So I simply suggested that the
fault needed workshop attention for
a few days. They still had their old
set, a Philips K9, which would serve
in the meantime.
And so the set finished up in the
shop. I left it for a couple of days,
partly to think about the problem
and partly to organise a discussion
with the National service department. It was just possible that they
may have already encountered a
problem with this picture tube.
But when I put it to them I drew a
blank. While they were well aware
of such a possibility, they had not
had any such problems. So I was on
my own.
At the first opportunity I gave the
set another try. It displayed exactly
the same pattern as before and, on
an impulse, I gave it another once
over lightly with the wand. And
Nevertheless, I rang the customer and asked her whether there
was such a speaker system and
whether it might have been moved
close to the TV set. Yes, they did
have such a system and one
speaker normally sat alongside the
TV set. In fact, it had been sitting
there when I called.
I realised later that if it had had
a mouth it would have bitten me. I
was just too intent on the TV set to
notice it and, as I said, I had pulled
the set clear anyway.
More to the point the lady was
quite adamant that nothing which
might be involved had been changed. The set was working perfectly
when they left the house on the Friday night, the house was empty until they returned on the Sunday
night and, at first switch-on, the set
was faulty.
There was nothing for it but to
return the set to the customer and
test it in its original environment.
The answer - nothing. Nothing untoward, that is. The set behaved
perfectly, even though I had taken
the trouble to ensure that it went
back exactly where it had been,
relative to the speaker.
Finally, I moved the speaker all
around the set and did everything I
could, short of shoving it inside the
cabinet, to create the fault. Nothing
worked; nothing I could do would
re-create the problem. And the set
has been running for many weeks
now with no hint of trouble.
So the mystery remains. Any
ideas, anybody?
~
AMATEUR RADIO
By GARRY CHATT, VK2YBX
Build this simple adaptor to receive
SSB on shortwave AM receivers
This project is about as simple as they come. It's a
455kHz oscillator that will allow you to receive SSB
signals on your AM-only shortwave receiver.
+5V
OUTPUT
1M
100pF
J
100pFl
Fig.1: a ceramic resonator is
used in a CMOS oscillator circuit
to give a 455kHz source.
build and will convert your AM
shortwave receiver to SSB reception.
AM & SSB signals
The parts for the 455kHz oscillator can be mounted on a small piece of
Veroboard. To demodulate an SSB signal, you simply wrap the output lead
several times around the receiver and tune for best quality audio.
Most experienced amateurs
know that SSB (single sideband)
reception requires a receiver fitted
with a "product detector" or BFO
(beat frequency oscillator) to
reinsert the missing carrier. They
also know that such receivers command significantly higher prices
than AM only models.
It's also a fact that signals broadcast using SSB tend to be far more
70
SILICON CHIP
interesting to amateurs and shortwave listeners than the standard
HF broadcasts, such as Radio
Australia, the BBC and the VOA
(Voice of America). The problem is,
most readers only have a standard
AM shortwave receiver - one
that's incapable of SSB reception.
This simple circuit solves that
problem. It uses only a handful of
parts, will cost you less than $5 to
To understand how the adaptor
works, it is necessary to explain the
basic differences between AM and
SSB transmissions.
A modulated AM signal consists
of a carrier and two symmetrically
spaced sidebands (see Fig.2). As
can be seen from Fig.3, the
amplitude of the carrier is a function of the amplitude of the
modulating signal.
The two sidebands on either side
of the carrier have the same
amplitude (Figs.2 & 4) and carry the
same information. This is why AM
is also sometimes referred to as
double sideband, or DSB for short.
In fact, the carrier itself conveys no
information. In mathematical
terms:
AM power = carrier power +
sideband power
= Pre + P(fc + fmJ + P(fc - fmJ·
Fig.2: the amplitude of an AM carrier is a function of
the amplitude of the modulating signal.
Fig.5: you can use an oversize drill to
cut the tracks on the Verohoard.
How it works
AMPLITUDE
le-Im
le
le+lm
FREQUENCY
Fig.3: a modulated AM signal consists of a carrier (fc)
and two symmetrically spaced sidehands (fc - fm
and fc + fm).
AMPLITUDE
The heart of the circuit is a
Murata "Ceralock" ceramic
resonator. This provides a reliable
455kHz source at a fraction of the
cost of a crystal. The resonator is
used in the CMOS oscillator circuit
shown in Fig.1 and provides an RF
output level of 5V peak-to- peak.
The output of the oscillator is
then fed to a length of insulated
hookup wire which is wrapped
several times around the receiver,
thus providing a degree of inductive
coupling. The amount of signal required varies from receiver to
receiver and can be adjusted by
varying the number of turns.
Construction
(fe-lmmaxJ
(fe-lmmin)
le (fe+lmmin)
(fe+lmmaxJ FREQUENCY
Fig.4: the two sidebands on either side of the carrier
have the same amplitude and carry the same information.
By removing one sideband and
the carrier, more efficient use of
the available transmitter power is
made without sacrificing the
transfer of information from
transmitter to receiver. In fact, an
SSB transmitter uses approximately one quarter the power of an
equivalent AM transmitter.
Another advantage of SSB operation is that the bandwidth required
to transmit the signal is significantly reduced. So, by removing the carrier and one sideband, we can
make more efficient use of the RF
spectrum.
Receiving SSB
To demodulate an SSB signal (ie,
to turn it back into intelligible
speech), it is necessary to insert a
locally generated carrier at the
receiver. This carrier can be
generated by using an external
oscillator tuned to the receiver's intermediate frequency (IF) - in this
case, 455kHz. The new carrier provides a reference frequency
against which the upper or lower
sideband can be demodulated.
Note that the opposite sideband
is also generated during this process, so that a complete AM signal
is available for detection.
OK, so that's how we convert an
inexpensive shortwave receiver to
SSB operation. It's an arrangement
that can be made to work quite well
but don't expect it to perform as
well as a fully-fledged SSB receiver
with narrowband IF stages and
special audio filters.
The unit can easily be made up
on a small piece of Veroboard. Fig.5
shows the wiring details. You can
make the cuts in the tracks using an
oversize drill. Note that all unused
input and output pins on the 4069
are grounded to prevent spurious
oscillation.
The recommended maximum supply voltage when using the
CSB455E resonator is 5 volts. If portable operation is contemplated, the
unit could be powered from a 9V
battery via a 5V 3-terminal regulator.
Because the ceramic resonator
operates at a fixed frequency, no
tuning of the circuit is required. To
demodulate an SSB signal, first
tune your AM radio to the SSB
signal (it will sound very distorted).
You can then wrap the oscillator
output lead around the receiver,
apply 5V, and carefully tune your
receiver for best quality demodulated audio.
Footnote: the CS455E ceramic
resonator is available from Dauner
Electronics, 51 Georges Crescent,
Georges Hall 2198 . Phone (02) 724
6982.
DECEMBER1988
71
NTAST
EWSTOR
ARRAMATT
Jaycar has opened a much LARGER \,
new store at Parramatta. We had to
reluclantly close the Carlingford
store as It was simply too small for~
our operation. We sincerely thank our~
Carlingford regulars for their patronage
over the past 7 years. Carlingford was
our first branch store and holds great
memories for us. Carlingford customers
should welcome the LARGER
PREMISES 10 minutes down
Pennant HIiis Rd to North
Parramatta Parking has VASTLY
IMPROVED. Don't forget ,to call in and
see Troy's familiar f;,.ce. We look 7
forward to being of more efficient<at>
service to youl
355-357 Church Street Parramatta
PHONE: (02) 683 3377
,
-~
t
~
lf/<
Buy a WELL PROVEN famous AVTEK Muttimodem and save a bundle. This stock
will not be replaced and FIRST BUYERS ONLY will benefit.
Multimodem Autoanswer II • BELOW COST • Vlatel COIT1)atlble,
1200f75 Baud, CCITT/Bell standard. Cat. XC-4822. Sold originally for $349, we have
reduced to $199,
A FEW LEFT at $125
auantitieslimitedsobequick.
Mini Modem II • BELOW COST •
Viatel, 1200f75 and 300/300. can be
powered by a computer directly, e.g. MlcroBee. Includes power supply.
$99 • BE QUICK
Cat. XC-4825
MegaModem Model V21, V22- Hayes "Al" corrpatible intelligent unit. A
few only at this price.
Cat. XC-4850
WAJ ~E~EMBER ONLY $250
Merry Christmas
ONIC ANVIL!!!
QUALITY JEWELLERS
SCREWDRIVER SET
yist. Hammer that IC into
r anvllll Weighs 2.7kg
Cat. TD-2040
Size 180mm long
BOmmhigh
Quality easy to use colour coded screwdriver
set with swivel plastic heads.
Screwdrivers include slotted 1.0, 1.6, 2.4,
3mm
Philips No. 0, 1
Supplied In transparent plastic case.
Cat. TD-2005
. 7"
$5.95
X
5" met
Grab a packet of these!
Pack ol 100 plated U-shaped staples with
soft-nylon saddle, you can hammer them In
to wood, particle board etc. Nylon saddle
cushions the wiring. Ideal for burglar alarms,
speaker flex, TV coax etc., and NO
expensive staple gun needed!
at. AS-3035
NLY $2 ea
~:.:~~~~-ultab; ;~;
AVE$6
Bargain 1: 1.25V MES lenshead globes.
Ideal for single cell torches .
,.
,4
USUALLy soe ea
25 for $2 (only se ea)
100 for $6 (only se ea)
1'j
Bargain 2: 5 volt MES torch globes.
Works OK on 6V.
~
soe ea
A.,e.,;
~
!P'
Bargain 3: 12 volt BC car replacement
globes suit tail lights, blinkers, garden
lights, etc.
1r
USUALLY ABOUT $3 ea
2for$1
~~ /
~
Bargain 4: 6 . 3 Vglobes
~MES
Cat. SL-2662
USUALLy soe ea
.
4 for $1
.·
·
10 for $2
·
· ·
100 for $15
Cat. SL-2654
Limited quantities on all globes.
metal black grill.
Cat. AS-3036
ONLY $3 ea
SAVE $7
Cat. SL2660
USUALLy
10 for$1
Insulated Staples No Staple Gun
Required
You would expect to pay about $8 for the
7 x 5 and $10for the 9 x 6 nornmally.
...C
_ ar
__B_o_n_n_ e_t______-1
Loc king DeYice
This device will lock the Bowoen Cable (i.e.
the 'wire' that goes between the bonnel
release handle and the bonnet catch)
AUTOMATICALLY when you switch your car
alarm on. The unit will give COMPLETE
under-bonnet security! The locking device
includes solenoid lock, control box,
emergency Bowden cable release, screws,
connector bracket and other hardware for
univers;,.i fitting. Instructions supplied.
Cat. LA-5400
A BARGAIN A T ONLY $19.95
WOULD NORMALLV COST
ABOUT $70
$13.95
30 PIECE ENGINEER'S
DRIVER SET
At lastl A driver set incorporating those
obscure shaped headsl
Have you flVer needed recently to service
an electric tool? Chances are you would
not have been able to do so because the
screws holding the appliance together
had strange shaped he;,.ds. Well now you
can with our 30 piece driver sell This sel
contains all the driver bits you are EVER
likely to encounter (See Below). Basic to
the set is an 8 1/2" Chrome-Vanadium
driver which will accept any of the 28
hardened steel bits supplied. They are
held into the sockel of the driver by a
small magnet - so you can use the driver
in any position. The screw-together
hollow handle will hold several tips so you
don, havetotakethe.wholesetwlth you
into the field . There is a tip here to suit
;,.Jmost any screw/nut you may come
across.
ankerflex,
MEDIUM SIZE: Suitable
for 3C-2V or RG58 coax
and heavy speaker flex.
Cat. HP-1186
$2.00
Here's what you get:
• 5 Slotted Bits 0-1, 3-4, 5-6, 8-10, 12
• 5 Hex Bits 3132", 5/64", 7/64", 1/8", 9/64"
• 4 Philips Bits No. 0, 1, 2 & 3
• 4 Square Recess Bits No. 0, 1, 2 & 3
• 6 Ton< Bits T10, T15, T20, T25, T30, T40
• 2 Pozldrive ·Bits No. 1 & 2
• 1 x 1/4" Drive Socket Adaptor
• 1 x 1/4" Drive Hex Bit Holder
And its all housed in a sealable tough
plastic case
WI DERANGE
MAGNAVOX BJX
$31.50
The SJX is as· twin cone speaker suitable
for medium power handling applications.
SPECIFICATIONS
40wans RMS
Power Handling
Resonant Freq.
44Hz
to - 12kHz
Freq. Range
93d8
Sensitivity
Cat. CE-2333
WOOFERS
MAGNAVOX SW
The SW Mk6 is a high fidellty woofer.
SPECIFICATIONS
Power Handling
65 wans RMS
Resonant Freq.
43Hz
to - 5kHz
Freq. Range
Sensitivity
96d8
Cat.CW-2109
MAGNAVOX BWR $36.50
The BWR is a high fidelity wide range twin
cones· driver.
SPECIFICATIONS
Power Handling
65 wans RMS
Resonant Freq.
43Hz
to - 12kHz
Freq. Range
Sensitivity
96d8
Cat. CE-2338
JAYCAR FOR MAGNAVOX SPEAKERS
MAGNAVOX 12W
MAGNAVOX 10W
12" woofer, medium power, low cost, high
The 1ow is a 1o· high quality, high power,
medium price woofer.
SPECIFICATIONS
Power Handling
75 wans rms
Freq. Response
30Hz - 5,000Hz
Resonant Freq.
33Hz
Cat. CW-2118
$43.50
$39.50
IIIIAGNAVOXBMV
8/30 Replacement
If you own a pair of 8/30 woofers, you can
now easily update them. Your old 8/30's
handle 30 wans rms, the new BMV's handle
120 watts rms. No need to buy new cabinets,
SMV's mount in the same hole, otherwise it's
a high quality, high power 8" woofer for most
applications.
SPECIFICATIONS
Power Handling
120 wans rms
Resonant Freq
31Hz
lo - 4kHz
Freq. Range
Sensitivity
96d8
Cat. CW-211 0
MAGNAVOX12MV
The 12MV is a high power high fidelity
woofer.
SPECIFICATIONS
Power Handling
150watts rms
Resonant Freq.
19Hz
Freq. Range
to - 3kHz
Sensitivity
96d8
Cat.CW-2125
$99.50
POLYPROPYLENE
MAGNAVOX
WOOFERS
JC 150 6" WOOFER
SPECIFICATIONS
Resonant Freq.
Sensitivity
Power Handling
Freq . Response
Cat. CW-2105
49Hz
95dB
50 wans nms
80-BOOOHz
Easy to use automatic connectors. Simply wrap around the
existing wire and new wire and squeeze.
NORMALLY $1.25 for 4 or 31~ ea
(Two styles supplied in pack)
PACK 15 for $1.95 (only 13e ea) Cat. HP-1207
PACK 100 for $10 (only 1oeea) Cat. HP-"1208
quality. 25mm voice coil wound on aluminium
former. Polyurethane foam roll surround.
SPECIFICATIONS
Power Handling
Freq. Response
Resonant Freq .
Cat. CW-2 122
$56.50
ULTRASONIC PEST & INSECT REPELLERS
• Frequency range 30kHz to 65kHz variable
• Output level 130dB
• Both units include 240V power adaptors
~fflil.l!
Single Transducer
ONLY $29.95
SAVE $10
WAS $29.50
NOW $17.95 SAVE39%
SASSO Mylar drivers, freq. reponse
DUAL TRANSDUCER
ONLY $39.95
WAS$59.50
NOW $39.50
SAVE 34%
For full details see our catalogue.
20Hz-25kHz . Quality muff pads.
Cat. AA-2022
Cat. YS-5512
WAS $39.50
CAR NEGATIVE ION GENERATOR
Now you can have all the benefrrs of your home ioniser in your car.
This great new Jaycar direct import is durable, stylish and compact, measuring only 110mm
in total length . It simply plugs directly into the cigarette lighter socket in your car. It can
generate large amounts of negative ions for purifying air, and some ozone for eliminating
odour.
Jaycar's direct importing cuts out the middle man and saves you money.
ONLY $34.95
NEGATIVE ION GENERATOR
iii
GREAT XMAS
PRESENT TO
YOURSELF
We are holding small stocks of
BRAND NEW valves going back to the
A~
l EMS
-
·
liquidate this current rrodel rrerchandise.
ONCE AGAIN their staggering loss
is YOUR GAIN.
OFFER No1
SAVE AROUND $200
Genuine NADY MODEL 201GT
Guitar wireless microphone link
which includes FM "True Diversity"
receiver, bodypack transmitter with
high impedance input (suitable for
guitar pickups, bass, sax, etc). The
body pack accepts a standard 6.5mm plug and the audio lead acts as the antenna. neat! The
body pack measures 96x60x203mm and weighs only 70 grams. It requires a 9V alkaline
battery. Both transmitter and receiver are crystal locked and offer 20-20,000Hz ±3dB
frequency response and 120dB (max SPL A-weighted) dynamic range. Output is line level
600 ohms. Minimum adverse operating range 200 feet, line-of-sight 1500 feet. Elsewhere you
will pay $800+ for this system in Australia. But, while they last you will be able to get this
product from us for only $5991 That's right, you WILL SAVE around $200 over the normal
price in Australia (Australian rec retail $799).
(If more than one is ordered they will be supplied on separate frequencies.
Cat. DT-5020
$599inctax
OFFER No2 SAVE AROUND $300
Genuine NADY 201 HT microphone wireless system comprising of YD-04 microphone
(virtually identical per1ormance to Shure SM-55), Integral antenna (no dangling wires) low
battery ligh1 and professionally rugged. Measures 222(L) x 36(Dia)mm weighs 232 grams.
Use 9V cell. Included of course is the 201 "True Diversity" receiver matched to the same
frequency. System performance and range are similar to 201GT above. (You see this system
used by TV tertainers in the US all the 1imel)
(If more than one ordered or 1 x 201GT and 1 x 201 HT ordered they will be supplied on
dttferent frequencies.)
cat. DT-5030
N.Z. Customers save further 150Yo on these Aust. prices!
DT-5020 $463 tax free
DT-5030 $543 tax free
SAVE 38%
Vintage Valve S ale
GENUINE ~ ~
FM DIVERSITY
WIRELESS MIC/
GUITAR LINK
SELLOUT
You would DIE if you knew where
we bought this shipment of brandnew genuine USmade NADY
wireless PA gear from! Suffice to
say that they lost a fortune to
NOW $24.50
..
••·
.
.
.:__ ~,
_, . , . . . .
.
Don't forget
Carlingford Store
now moved to
Parramatta
355 Church Street
Phone (02) 683 3377
240 VOLT - SAVE $50
Cat. YX-2905
•
t
$ 699 lnC
ax
Top of the range, excellent sound.
Quality phones. Cat. AA-2023
Features Mylar drivers, sponge earpads,
metal 3.5mm stereo plug. Cat. AA-2021
Cat. YS-5510
SPECIAL INTRODUCTORY OFFER
DIGITAL STEREO HEADPHONES
SA888
p&p fixed cost $20/unlt
~::ra~~ob:r;~!nt types are available
but most are in very small quantities.
Stock will not be kept at local stores it will have to be ordered in for you
against pre-payment. This does not
guarantee that the stock may have
already been sold. All the valves are
one price $5 ea. If sold out money
refunded in full. Stock is new but NO
WARRANTY is offered. Normal mail
O.K. See list of part numbers:
6FC7-SBY7-SCG7•6CK6•6CHS-6AU5Gl•6BJ6
•6AN8A•6BA8A•3V4•1 R5•1 S5•6AL3•6AK8
•6BMS-6EM7•6SA7GT-SBH8•6S2•6CM7•5AS4
•6BX7GT-SBW7•6BS8•6BN6-SB R5•6BK7B
•6BJS-6BJ7-SBFS-6BE7-SABS-6AC7•6AH4GT
•6AB5•6A6•6AB4•6AG5•6BD6•6BD5Gl•6BC8
•6AU7-SBC9Cr6AS8•6AQ6•6ANS-6AS5•6AQ7
•25Z4G-2SZ5•12ATS-UF41•9AO&12AS-117Z3
•9AKS•6YSG-7AN7'12AUS-12AX4GTB•12BD6
•12BV7•12BA7•1207GT•12K7GT•12SA7•12SG7
•12SO7GT•12SN7•12SK7GT•15A6•21AS-16A5
•15DQ8•6SC7•6AU4GT•6S R7•6SH7GT
•6CD6GA•6CDS-6BO6GT•6DB5•6DA5•6DE6
•6DS8•6ES6•6EV8•6ET6•6C6•6B27•6CF6
•EC86•6CM4•6CQ6•6DA4•6N3•6J N8•6G6
•6F8G•6W6GT•6R7•6N7•UCH21•UCL83'UY1 N
•UCH42'UCH41 • 1AB& 1A& 1A5GT• 1ABS-PCL83
•UBL21 •EM87•PGL83•DL93•3A5•3A4•3Q4
•3O5GT •5GK3•E R4GYB•5U8• 1D7G• 1DBGT
• 1F6•35C5•50ENS-32L7GT •C8•C1 •6AN8A
•6BH8•6BVB• 12AC.5•12AN7•6AW8A•6AD8
•6EH7•6BQ6GTB•6BQ7A•6BZ6•6AB8•6BF5
•SAM 5•6CM 7•6BH8•6B U8•6AT6•6AD8
•6EM5•6EB8•6V9•6X2•6W6GT•6N8• 12AA6
•12BAS-12BE6•6U8•6CW7•6CD6•6DQ5•CB 1C
•CF1 •CY31 •6CD6GA
ALL ONE PRICE
$5.00 each
Machined
Aircraft
Grade
Aluminium
Flash light
What an excellent product! It measures
145mm long and runs off 2 - AA batteries.
It is 70 times brighter than a normal torch
and the beam is adjustable from spot to
beam, and it's waterproof &nd shockproof.
Durable anodised abrasion resistant finish,
with a non sl~ knurled grip. This torch will
last a lifetime. Small enough to fit inside a
car glovebox or handbag. It can also be
used as a lantern. Unscrew the top and the
bulb is exposed to give 360° light.
We have seen these torches for $19.
We have direct imported them and can
offer them for the amazing price of only
$9.95.
Spare bulbs available for only $1 .50 (Cat.
ST-3002)
Cat. ST-3000
({---
ONLY$9.95~
Quality Stacking
Banana Plugs
• NEW RANGE OF COLOURS I
• NEW LOWER PRICES!
RED
BLACK
GREEN
BLUE
YELLOW
Cai.
Cat.
Cat.
Cat.
Cat.
PP-0390 were $1.95
PP-0391 were $1.95
PP-0381
PP-0382
PP-0383
10+ $1.10 ea
ONLY
$l .2S ea
THE LATEST KITS
120WAITPA/
GIDTARAMP
MODULE
Ref: Silicon Chip November 1988
This rugged Mosfet amp module is
designed specifically to drive a 100V line
transformer for PA. It can also be used for
guitar and stereo amps,
Short form kit. PC board and all
components supplied, including Mosfets.
No power supply parts or heatsink
included in kit.
Heatsink extra Cat. HH-8550 $22.95
Cat. KC-5043 (kit)
OUR MOST POPULAR KIT IN 1988!
FM Stereo Transmitter ''MINI MIITER"
CAR SAFETY
LIGHT
Ref: Silicon Chip October 1988
This fantastic project enables you to transmit
a signal IN STEREO over the FM band. The
range is limlted to about 20 metres or so, so
it's not a nuisance to anyone else. It uses a
single 1.5V M (penlight) cell which lasts for ages.
Just imagine I You can listen to your CD player
on your FM headphone receiver while washing your
earl You can play your Walkman CD player over
your car stereo - no wires I The possibilities are
endless I Set up your own micro FM Radio Station I
The Jaycar kit of this project includes the hard.to get
Rohm BA1404 chip and the CORRECT 38kHz
crystal - even harder to getl All other specttied
parts are included as well.
Cat. KC-5041
Ref: Silicon Chip November 1988
Is your car in danger of being sideswiped at
night? This project detects an approaching
cars' headlights and'automatically turns on
the brake lights to warn the driver. The brake
lights switch off 5 seconds after the car has
passed. Circuit is disabled during the day.
Quallty Philips LDRs supplied
Cat. KC-5044
$29.95
$72.50
$29.95
POWERMATE2
"KNIGHTRIDER"
LED SCANNER
Ref: Silicon Chip November 19:JB
Provides the scanning effect same as on
kit car In Knightrider TV program. Use for
burglar alarm applications, novelty
applications on kids toys, etc. PC board
and all components supplied.
Cat. KC-5042
Refer: EA October 1988
Revamped version of original Powermate
power supply. Delivers clean, crisp
regulated 13.8V DC at up to 5 arrps.
Full kit.
Ref: EA November 1988
Low cost 4 digit timer which can measure
imervals from a few microseconds to hundreds of seconds. You can measure the
speed of a slug from an air rifle, gott ball
speed, etc.
Short form kit, no box o, front panel supplied.
Cat. KA-1708
$119
STROBOSCOPIC TUNER
KIT Ref: EA July 1986
Cat. KA-1707
This simple circuit provides
crysta~locked accuracy
for tuning virtually any
musical Instrument.
It also doubles as a
stable frequency
reference tt you prefer
to tune up by ear. Kit
includes box and all
parts.
Cat. KA-1706
$59
$17.95
HANDS FREE
TELEPHONE
HEADSET $16.95
WIRELESS DOORBELL
Ref: Silicon Chip August 1988
What a great idea. A wireless doorbell with
the option to have as many sounders as
your house requires.
Transmitter is mounted in a UBS Jiffy box
with a pushbutton switch which mounts
outside your front door. Powered by a 9V
battery. Receiver mounts in plastic box and
requires 12V DC plugpack, our MP-3006
will do $14.95. Use as many receivers as
you require.
TRANSMITTER
KIT
RECEIVER KIT
$47.50
So new, we don't even have a picture yet.
As used with the Silicon Chip speakerphone
project.
Headset,
microphone
with
lead and
3.5mm plug. Mini size ultra lightweight.
Cat.M-2018
'
SPEAKERPHONE
Ref: Silicon Chip Sept 1988
High quallty hands free telephone adaptor
that works extremely well.
Full kit including box, panel, isolating transformer and all parts.
Cat. KC-5040
ONLY $89
PLAYMASTER/JAYCAR 60/60 BLUEPRINT
AMPLIFIER
Standard version still available
Cat. KA-1652
$369
Cat. KA-1650
See our catalogue for full details
3_2_9___ _ _ _ _ ____
L...$,.__
Ref: Silicon Chip November 1988
Ideal for those who want to experiment
with plasma displays. This kit is basically
just the power supply. You can use a
240V globe anywhere up to 300 watts.
(Warning with this unit you can not touch
the globe whilst it is operating). Features
adjustable display. Kit includes PCB, EHT
transformer, box and all components, but
not globe and holder (which are readily
available).
Cat. KC-5045
$75
UPGRADEDS000BLACK
MONOLITH POWER AMP
RE-BORN WITH
TOPOLOGY MODULES
Cat. KE-4200
$499
HEAD OFFICE
MAIL ORDERS
POST & PACKING
137
rrrr•~!_i_i_i_2_f_J_)~:~:~~~;_:_:_:_:_:_:_ _ _ _ _~_t_{_~_1_l_?_~-~~l-~~;-~_:_~_:~__
_M.:~~, ff
VISA
1
i_:_R$_1oo_~_f_H__iJ_oi_:_ _
MAIL ORDER VIA YOUR
ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50
SYDNEY - CITY 117 York St. (02) 2671614-
GORE HILL
188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 - 5.30 Sat 9 -4pm
PARRAMATTA
BURANDAQLD
144 Logan Ad (07) 393 0777 Mon-Fr, 9 - 5.30 Thurs 8.30 - Sat 9 - 12
__E '
::::;;:LE
Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12
355 Cl'uch SI (Cnr. Vtctoria Rd) (02) 683 3377
Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 2pm
115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 -12
MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030
121 Forest Rd (02) 570 7000 Mon-Fri 9- 5.30 Thurs 8.30 pm - Sat 9 -12
SPRINGVALE VIC
Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12
887-889 Springvale Road Mulgrave (03) 5471022
Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 -
~
THE EVOLUTION OF
ELECTRIC RAILWAYS
In the space of about ten years or so,
diesel electric locomotives completely
displaced all the hundreds of thousands
of tried and proven steam locomotives
that had served well for one hundred
and twenty years! Why?
By BRYAN MAHER
Herr Doktor Rudolph Diesel (Germany, 1858-1913), inventor of the
internal combustion engine which
now bears his name, envisaged a
simpler and more efficient engine
than the system pioneered by fellow
German Karl Benz in 1878. The
76
SILICON CHIP
diesel engine needs no electric
spark nor carburettor, only a
piston, cylinder, two valves and a
pump to inject fuel oil under high
pressure.
When the piston has drawn air
into the cylinder and compressed it
to a high pressure and temperature, a small quantity of fuel oil is
injected to cause self-combustion.
This drives the piston down and
turns the crankshaft. Herr Diesel
originally intended his design for
airplane propulsion but his first
successful engine in 1897 was too
heavy to fly.
Consequently he turned his
thoughts to diesel ship propulsion.
His engine was more efficient than
some of the reciprocating steam
engines in shipping use at the time.
Sadly his life was cut short, for he
died in mysterious circumstances in
1913. After boarding a ship bound
for England he apparently disappeared en route and was never
seen again.
It was before the outbreak of
FACING PAGE - AMTRAK'S TURBOLINERS represent a blend of American and French design with their modern lines
and comfortable interiors. Seven of these red, white and blue "turbos", built by Rohr Industries in California, are used
on inter-city rail services. The photograph above shows an early NSW SRA diesel-electric passenger train. These trains
were used on NSW country routes but have now given way to the recently introduced XPT.
World War 1 and he might have
been walking a political tightrope,
as his 4-stroke diesel engine had
potential for naval ship propulsion.
The four "strokes" of his engine
piston are air intake, air compression, power (fuel burning) and exhaust. Thus power is delivered on
only one piston stroke out of each
four; ie, one quarter of the time.
Later Sir Dugald Clerk of England extended the diesel design to
give one power stroke every time
the piston travels downwards and
one compression stroke on each upward movement; ie, one power
stroke out of each two. This is called the "2-stroke" principle, which
gives power one half of the time.
Compared to a 4-stroke engine,
the 2-stroke design gives more
power for a given size and weight
but its efficiency and fuel consumption may be greater or less depending on the construction.
Since those days the diesel
engine has pervaded every area of
the transport industry, some ships
today having engines so large that
you would climb up two flights of
stairs to go from the crankshaft
floor to the cylinder head level.
Their pistons can measure a metre
in diameter and have a piston
stroke of two metres.
First diesel electric
In 1913 the Mallesta and Sodermanlands Railway Company of
Sweden made history as the first
railway to use diesel electric propulsion regularly. But because
diesel oil was scarce in Europe and
hydro-electric power available, the
Swedes retained their preference
for electric railway traction. Today
in Sweden there are only 533 diesel
electric locomotives compared to
726 electric locomotives.
But that little Swedish experi-
ment did not go unnoticed on the
other side of the world. In the USA
the motor car and truck firm
General Motors (GM to most people)
had observed the advantages of
diesel electric railroad propulsion
and thought well ahead.
We remember that in the period
1900 to 1930 the American steam
locomotive had grown from 100 tonnes to over 500 tonnes, featuring
designs with up to 24 driving
wheels, such as the Erie Railroad's
2-8-8-8-2 monster built by the
Baldwin Locomotive Works in 1914.
The Mallet type loco itself weighed 384 tonnes and had an enormous
tender carrying 37,850 litres of
water (37.85 tonnes) and 16 tonnes
of coal. This loco featured six steam
cylinders each 91cm (3 feet) in
diameter, working in compound
with a boiler pressure of 1448
kilopascals (210psi). The tractive
effort exerted was 72.7 tonnes.
DECEMBER1988
77
AMTRAK'S "MINUTE MAN" HEADS for Boston on its way from Washington, near Warwick, Rhode Island. Although
the Northeast Corridor is electrified between Washington and New Haven, diesel-electric locomotives are used the rest
of the way to Boston. To ensure crew safety, the windscreen is bullet proof and can withstand the impact of a concrete
block at speed.
More powerful still was a
2-10-10-2 articulated steam
locomotive built by Baldwin for the
Virginian Railroad in 1918. Its
largest cylinders were 1.22 metres
(4 feet) in diameter and when all
cylinders were fed with full steam
pressure at 1483kPa (215psi) this
locomotive produced a tractive effort of 79.38 tonnes (175,000lbs).
Would you believe that it was the
enormous power and tractive effort
produced by these monster steam
locos, the largest ever built, which
produced the decline and death of
the steam locomotive worldwide
and the rise to dominance of the
diesel electric locomotive?
If you find that that strains
credibility, consider if you will the
following sequence of events.
Single large locomotives
American Railroads could be
divided into the coal carriers (Virginian, Erie, Norfolk & Western, and
78
SILICON CHIP
Chesapeake & Ohio Railroads) on
the eastern side of the country and
the long-haul freight carriers
(Union Pacific, Santa Fe, etc) whose
tracks crossed the western Rocky
Mountains to the Pacific coast.
The eastern coal carriers
naturally leaned towards steam
locos as coal and water were near
at hand, tenders could be refilled
often and their routes were not too
long.
All the eastern coal lines had to
surmount the Appalachian and
Allegheny mountains of Virginia
and West Virginia on their way to
the Atlantic Ocean export ports of
Chesapeake Bay.
Their monstrous locomotives
single-handedly hauled coal trains
of 7000 tonnes up the mountains on
1-in-62 grades and dragged 15,000
tonne trains on the coastal plains to
the ports. But why not use two
smaller locomotives in double-head
mode?
There were two reasons: (1) the
difficulty in synchronising the starting of two huge steam locos; and (2)
the cost of the extra loco crew of
three (driver and two firemen).
This led to the concentration on
single huge locos.
In contrast, the long-line freight
railroads such as Union Pacific had
to carry coal (and even water)
thousands of kilometres to their
locorefuelling points. In 1942, Santa Fe were hauling more than 200
large water tank wagons daily to
quench the thirst of their steam
locos running between Winslow,
Arizona, through Flagstaff to
Barstow, California.
Thus in America the western
Rocky Mountains were crossed by
beautiful steam locomotives, each
with a tender as big as a ship in
tow. The 6000hp (4.5MW) "Big
Boys", the largest Union Pacific
steam locomotives, had a tender
carrying 32 tonnes of coal and 110
tonnes of water. Two 16-wheel
bogies were needed to support the
nearly 200 tonnes of the tender.
Australian inland railways had
the same problem. Many a reader
will remember outback steam
passenger trains which included a
large water tank truck immediately
behind the loco tender.
The Australian National Railways by necessity carried huge
quantities of water between Port
Pirie and Kalgoorlie. The classic
steam loco used to cross the Nullarbor Plain was a copy of the NSW 36
class but with an oversize tender
which weighed more than the loco!
Such a line was ripe for the
diesel electric salesmen!
Enter diesel electrics
Herr Doktor Diesel's first effort
at rail traction in 1913 was a
failure because he attempted direct
drive from the engine to four coupled wheels. His 4-4-4 locomotive ran
but was unpopular.
The Swedish idea, pioneered by
ASEA, used the diesel engine to
drive a DC generator which
powered electric traction motors,
giving better control of speed and
starting.
By 1924 the first diesel electric
loco appeared in the USA. Though
only 300hp (334kW), this yard switching loco built by American
General Electric Company was the
beginning of an era. The world's
first diesel electric loco for export
was also produced in 1924 but it
came not from the USA. It was an
ASEA 200hp (149kW) Bo-Bo
locomotive exported to Tunisia. It
was a great success.
In the same year both Austria
and Germany were experimenting
and Brown-Boveri/Fiat built a
440hp (328kW) diesel electric for
service in Italy. In 1933 Germany
had a diesel electric "Flying Hamburger" train running between
Berlin and Hamburg. It covered the
285km in two hours eighteen
minutes, averaging 123km/hour.
Still, American railroads had
steam hauled trains that ran faster.
For example, the Santa Fe had to
run some trains at 160km/hour to
keep to timetable.
So why did diesel electric traction demolish the steam locomotive?
TWO POWERFUL CONRAIL Bo-Bo diesel electric locomotives are shown here
hauling a heavy freight train. Each loco is an EMD Model GP9 weighing 114
tonnes and rated at 1.3MW (1700hp). The diesel engine is a 16-cylinder Model
567C which is direct-coupled to a DC generator.
Cost comparisons
Was the answer prime cost? No,
not at all, for the big American
manufacturers, like the Baldwin
Locomotive Works, could turn out
three steam locomotives per day,
each costing only one third that of a
diesel electric unit of equivalent
power.
Perhaps readers think that the
cost of servicing a dirty steam
locomotive for each 1000km run
was more than the cost of keeping a
diesel electric on the road? Not
necessarily so.
Many countries, including Australia, serviced their old steam
locomotives in ancient, ill-equipped
running shops. In 1940 it was still a
practice at Eveleigh shops in NSW
for candles to be used for illumination when lubricating the valve rods
between mainframes in 50-class
steam locos.
Contrast that with the modern
Norfolk & Western Railroad running shops in the USA which could
service a 500 tonne giant steam
locomotive and have it out on the
road again in 50 minutes. And that
included a complete clean, lubricate and refuel job, including
cleaning inside the smokebox.
It was entirely unrealistic for
Australians in 1950 to compare the
maintenance cost of a NSW
50-class steam freight locomotive,
then 60 years old, with the 40-class
diesel electric, in those days the
latest thing on twelve wheels. The
40-class of 1650 hp (1.23MW)
lasted about thirty years, about half
the life of many steamers.
A further complication arose
with these diesel electrics: an instruction was issued that should
they ever suffer a simple derailment, the diesel engine was to be
stopped and not restarted until the
maintenance workshop had stripped the engine down and tested the
alignment of the long crankshaft!
A more realistic comparison in
1950 would have been to compare
diesel electrics with the newer
38-class steam locomotive. This
was a beautiful machine, very fast,
whisper quiet, powerful, and using
local coal and water instead of imported diesel oil.
No, maintenance costs were not
the reason for the steamers'
demise.
To see why diesel electrics conquered the world, we must look at
the biggest and most successful
American steam locomotives.
Efficiency and running cost
Was it the inefficiency and running costs of steam? No, running cost
was not the the reason. The Norfolk
DECEMBER 1988
79
AMTRAK'S P-30CH DIESEL-ELECTRIC locomotives are built by General Electric for medium and long-haul routes. These
powerful 6-axle Co-Co locomotives are rated at 2.24MW (3000hp), have a top speed of 165km/hr and weigh 176 tonnes.
and Western Railway resisted the
diesel electric demonstrations as
late as 1960, showing that their
very large modern steam locomotives could equal or outperform
any diesel electric units on running
costs alone.
Those tests were conducted hauling equal train tonnage over the
same tracks at equal timetable.
The running costs (per tonne
hauled) of the huge steam locos
were so low simply because those
locomotives were so big. One 3-man
loco crew could haul any train of
the day up any mountain. But competition between railroads being
fast and fierce, there was continual
striving for yet bigger locos to haul
even longer heavier trains. And by
the 1930s the design of large steam
locos had reached the absolute
practical limit.
Any increase in steam loco
power must mean higher steam
80
SILICON CHIP
pressure. This in turn requires
larger fire grate area or a larger
boiler and cylinders. But the boiler
and cylinders could not be increased further in diameter otherwise
the locos would not fit through the
tunnels.
For the same reason, the height
could not be increased. The
American locos were already up to
a metre taller than many Australian machines.
Boiler problems
No, the only boiler dimension
which could be increased was the
length. Such an increase could
restrict running speed on curves
but there is a more critical problem.
An overly long boiler has trouble
with its fire tubes which run the
length of the boiler from the firebox
to the smokebox at the front.
If the boiler is too long the fire inside those tubes goes cold before
reaching the front and boils no
more water. So increased boiler
length gains nothing.
They just could not build larger
steam locomotives.
Therein lies the reason why
diesel electrics won the survival
battle. Diesel electrics had the advantage that railroads could couple
as many together as they needed to
pull a given train and only one loco
crew was required.
The result? The 175,000 steam
locomotives built in the US over the
past 120 years are now gone, entirely replaced by 27,000 diesel
electrics and a few hundred electric locomotives. And the rest of the
world followed suit, largely because they had to.
The big three American steam
locomotive manufacturers Baldwin, The American Locomotive
Company (Alco) and Lima - all had
trouble seeing the diesel electric
ECONOMY
TRANSFORMERS
1-9
ARLEC SUPER TOOL
10 +
2155 240 V6-15V 1A
Cat. M12155
$9.95
$8.95
2156 240V 6- 1SV 2A
Ca t. M1 2 156
$14.95
$13.95
2840 240V 9V CT
Cat. M1 2840
-
$5.95
$4.95
2851 240V 12-SV CT 1SOmA
Cat. M1285 1
$5.95
$5.50
2860 240V 15V CT 250mA
Cat. M1 2860
$5.95
$4.95
6672 240 V 15-30V 1A tapped
Cat. M1 6672
$14 .95 $13.95
DB25 CONNECTOR
SPECIALS!
TYPE
1-9
gp
PASSIVE INFRA RED
DETECTOR
Compact P.I.R. with adjustable
corner or wall mounting bracket,
dual pyroelectric infra red sensing
element gives a coverage 2 x 14
zones 2'!1 high and 1Orn wide.
• Sensitivity adjustment control
• Detecting rang e 12- 15 metres at
90 degrees
• Detecting zones 9 long (up)
5 short (down)
• LED indicator for wal k test. {can be
disabled)
• Shielded against RF interference
• Relay output NC or NO at 30V
(AC-DC) 0.5A max .
♦ Integral NC tamper switch
• Operating voltage 10.5 - 16V DC
• Current 20mA with LED 25mA
$0,70
$0,70
$0 ,60
$0,70
$ 0,70
$0,70
$ 0,70
$ 0,75
$0 ,70
9S
9C
15P
15S
15C
25 P
25S
25C
10~
$0,60
$0 ,60
$ 0 ,50
$ 0,65
$0 ,65
$0 ,60
$0,60
$0,65
$0,60
100
!
$0 ,50
$0 ,50
DB 25 CRIMP SPECIALS !
Type 1·9
Female $2.95
Male --- S2 ,95
10
White durable pl astic. 8 ohms
Cat. C120 10
Normally S11.95
1-9
10 1
SPECIFICATIONS:
• Input 3•5mm stereo phone plug.
Impedance 32 ohm.
• Mono/~tereo switch has plug
mountrng clip.
• FM Transmission approx.
90·35MHz (Tuneable 89· 91 MHz )
• Range 15 metres. (below 15mWm
at 100 metre s)
• Power 1 ·5V AAA size batteries
(100 hours continuous use )
• Size 72x 38 x 21mm
S7.95
A16100
$0AO
$0 ,60
$0 ,60
$0,50
$0 ,50
$0,60
$0 ,50
100 +
S1.95
SL95
!
S2.50
$2,50
10W HORN SPEAKERS
$6.95
$64,95
$69,95
SPECIAL. ONLY $12.95
~~;:::;::~~•c,-
CAR AUXILLIARY
STOP LIGHT
RCA GOLD PLATED
PLUGS AND SOCKETS
For those who need the ultimate in
connection . Essential for laser disc
players to get that fantastic sound
quality
Plug Cat P10151
$2.95
Socket Cat P10150
$2.25
-
Verbatim
NICADS!
Save a fortune on expensive
throw away batteries with these
quality Nlcads and Rechargers!
QUALITY 3mm LEDS
Cat. No. Col.
Z10140
Z10 141
210143
210145
Da!aLlfe,
$39,95
$46.95
$99,00
$22.00
$26.00
$75,00
$41 ,00
1-9
$0,15
$0,20
$0,20
$0.20
10-t-
100 ._
$0.12
$0,15
$0,15
SO,15
$0, 10
$0 ,12
$0 ,1 2
$0, 12
Cat.No. Col . 1-9 10 t
100 ,
210150 Red $0,08 $0 ,07 $0,06
210151 Grn $0 ,15 $0,12 $0 ,10
210152Ylw $0,15 $0,12 $0 ,10
$37,95
$43.95
$89,00
$21 ,00
$24,00
$70,00
$39.00
til/1~ffir·-·:·:~ Ill
disks that are probably the cheapest
in Australia ! They even come with a
life time warranty! So why pay 2-3
limes the price for the same quality?
$9.95 $9.50 $8.95
S9.95 $9.50 $8.95
PI 0966 3 PI N CHAS IS FEMALE
$4.95 ,, .......... ,,.,.,,.,. $3.95
$49.95
Red and white twisted
Conductors: 2 x 1 strand 0.17mm
Sheath: 0 .0 . 2 x 1.3 5mm
$19.00/m
10 ➔
rolls
$17,50/m
CAR ANTENNA BOOSTER
• In-line instalation
• 12v boosts 100%
Cal, A12073 ,,,,,,,,,,,,,,, ,,,,
$7.95
$6·25
(ALL PRICES PER 10 DISKS)
5¼" HIGH DENSITY
(ALL PR ICES PER 10 DISKS)
5¼" DISK STORAGE
(DD100-L)
Efficient and practical. Protect your
disks from being damaged or lost!
Features ...
• 100 x Sl/4" disk ca pacity
3½" 2S/2D DISKS
IO+DISKS IOO+DISKS 1.000+DISKS
$22
$21
(ALL PRIC ES PER 10 DISKS)
~~~r:e~J~8Js2Jlv
•
•
•
•
Smoked plastic hinged lid
Lockable (2 keys supplied)
High impact ABS plastic base.
Contemporary design
Cl 6020 ,,,,,,,,,,,,,,,,
only $15.95
MINIATURE HOBBY VICE
• Lever operated suction grip base
for instant mounting and portability
• Mounts on smooth non-porous
surfaces.
• Ideal for holding components, and
o ther small/light objects.
CatT12458
_ only $6.45
1 99
JA RY INTER·
STATE DUE TO FREIGHT COSTS
MAIL ORDER:
PORTASOL
PROFESSIONAL
METEX
M-3650
MULTIMETER
• Four tools in one · Blow Torch .
Hot Blow, Hot Knife
• No Cord s or batteries
• Heavy duty, tip lemperature
adjuslable up to 400° c .
• Equivalent to 10·60 watts
• Hard working. Average conllnuous
use 90 minuters
• Refills in seconds
• ~owered by standard butane gas
lighter fuel
• Range of easily replaceable screw
tips included
• Includes metal stand for the
soldering iron when workin g
• Cap features built-in flint for
igniting Portasol tip
• Includes snap case for storage
Cat. T12639
$89.95
20A, 3 112 digit frequency
IO+DISKS IIIO+DISKS 1,IIOO+DISKS
$23-95 $22·95 $21 ·95
305 Morphett St, ADELAIDE
counter multimeter with
capacitance meter and
transistor tester.
5¼" 2S/2D DISKS
(DOUBLE SIDED)
IO+DISKS 100+DISKS 1,IIOO+DISKS
Phone : (03 ) 543 7877
SOUTH AUSTRALIA:
Electronic Discounters P/L,
7-2VNICAD
RACING BATTERY PACK
S 15025
Packs of 10 , 2S/20 without boxes,
or brand name, just their white paper
Jacket and index labels.
(5 1/4 " disks includes write protects) .
$6·50
Phone : (03) 489 8866
CLAYTON : 56 Renver Rd _
RACING BATTERY PACK
QUICK RECHARGER
B~
STANMORE_ 2048
Phone : (02) 519 3134
Fax: (02) 519 3868
Phone : (03) 663 6151
~
Suits most Tamiya and other bran d
remote control cars, toys, and models.
SPECIFICATIONS,
Voltage: 7·2
Charging Current: 130mA
Nominal Capacity: 1300mAH
Charging Time: 15 Hours
SYDNEY: 74 Parramatta Rd ,
NORTHCOTE: 425 High St
P 10962 3 PIN CHASlS MALE
$4.50 ...... ,, ,, .,, ... ...... $3.90
RODIRVING
ELECTRONICS
MELBOURNE: 48 A'Beckett St
P10960 3 PIN LIN E MALE .
Cat.W
1-9 rolls
GOLDSTAR
12" TTL MONITOR
X14500 GREEN,,, only $99
X14502AMBER, only$99
10 OR MORE $95 EACH
,iin-
$3,90 ,,. ,......... ,,.,,,,,, $3,50
Pt0964 3 PIN LI NE FEMALE
"NO BRAND"
DISKS
Now yo u can buy absolute top quality
1.2 A .H.
1 .2 A .H.
$12.95
10 +
$3.00 ,,. ,, ,.. ,........... ,, $2.50
di
C
D
A12090
M23528 ,,,,,,,,,.,,,,,, $39.95
CANNON TYPE
CONNECTORS
1·9
Size Oesc.
1-9
10+ 100+
AA 450 mA.H . $2.95 $2.75 $2.50
Avoid rear end collisions wi th this
simple and proven method . A very
cheap forn:i of " insurance" ! Simple
to install with self adhesive rubber
mounting. 12V DC and 2 metre cable.
GOLDSTAR 20MHz
COMPOSITE MONITOR
X145 14 GREEN _, only$89
X14516 AMBER , only $89
10 OR MO RE $85 EACH
ina:~fhf ~~ehf8 rJ~~~e~~1fgh~!~~~:!
protected
Output: standard racing pack lead
and terminal to suit S15025 and
Tamiya 7·'?.V baneries
Char~ Time:Standard charge is
15 minutes for 7·2V baneri es
0-30 minute timer.
f111ii'a'1,;;1,1
ALL PRICES PER PACK 10 DISKS
DESCR IPTION 1-9 packs 10 + packs
3½" lS/20
3 ½ " 2S/20
3 ½ " 2S/ HO
1 S/20
20/20
2S/40
2S/ HO
Red
Grn
Ylw
o,a
QUALITY 5mm LEDS
VERBATIM
DISK SPECIALS!
$23
Cat. T12300
FREE STANDING, FOLD
UP MAGNIFIER
An ecconomicaUy priced ··hands free "
magnifier . !ets you take care of all
those tricky fine detailed )0 bs so
often encountered in electronics. o r
any of many other practical uses
such as home. work. hobbies etc.
Cat. T10020
Normally S14.95
$145
Cat.S15075
$6·75
This unit was developed to allow
portable compact disc players to be
used in cars by transmitting the
headphone output signal directly in
to your stereo FM car radio. It will
also transmit any mono/stereo signal
from any headphone output to any
FM receiver.
A versatile 12V electric tool tor
• Sanding
• Engraving
• Grinding
• Polishing
• Cutt ing
• Drilli ng
• Milling
• Erasing . el c
Features:
Operates on sale . low 12 volts from
ma1ns .electnc1ty via AC adaptor
(supplied ). li9ht and easy 10 handle
with touch switch and lock for
continuous running High torque
motor. 10.000 A.P M Can drill 2mm
holes in steer. 2 year guarantee
Contents:
• 12V Super Tool
• Plugpack AC adaptor
• 1 spherical milling cutter
• 1 wire brush
• 1 grinding wheel
• 4 drrtl bits. 0.6. 0.8, 1 0. 1.2mm
• Set of 5 chuck collets
• 6 eraser sticks
• Instruction sheets
This spectacular, rugged and
compact DMM has a bright yellow
high impact plaslic case. It features
a frequency counter (to 200kHz).
d iode and tran sistor test. continuity
(w ith buzzer). capacitance meter. up
to 20 amp current measurement and
comprehensive AC/DC voltage,
current and resistance ranges.
CHEC K THESE FEATURES,,,,
• Push-button ON/OFF switch
• Audible contin uity test
• Sing le function, 30 position easy to
use rotary switch fo r FUNCT ION
and RANGE selection.
• Transistor test
• Diode test
• Quality probes
• 1,2 " High contrast LC D.
• Full overload protection
• 20Amp
• Built in tilting bail
• Capacitance meter
• Instruction manual
091550 ,,,, Normally $165
Special, only $129
Local Orders: (03) 543 7877
Interstate Orders : (008) 33 575 7
All Inquiries : (03) 543 7877
CORRESPONDENCE:
P,O , Box 620 , CLAYTON 3168
Telex : AA 151938
Fax: (03) 543 2648
-
MAIL ORDER HOnlNE
008335757
(TOLL FREE, STAICTlY ORDERS ONLY)
LOCAL ORDERS &
INQUIRIES f03J 543 7877
POSTAGE RATES :
$1 - $9.99
$10 - $24,99
$25 - $49,99
$50 - $99,99
$100 - $199
$200 - $499
$500 plus
The above postage rates are for
basic postage only , Road Freight ,
PANEL METERS
GALORE !
We have a great rang e of panel
meters at great prices '
Cat.No.
Description
Price
010500 MU45 0-1mA
12.50
010502 MU45 50-0/50uA 12.50
010504 MU45 0-100uA
12.50
010510 MU45 0-5A
12.50
010518 MU45 0-1A
12.50
010520 MU45 0-1A
12.50
010525 MU45 0•20V
12.50
010530 MU52E 0-1A
14 .50
01 0533 MU 52E 0·5A
14.50
010535 MU45 VU PMetre 14.95
010538 MU65 0-50uA
16 .95
01 0540 MU65 0-1mA
16.95
010550 MU65 0- 100uA
16.95
0 10560 MU65 0-20V
16.95
bulky and fragile items will be
charged at different rates .
All wholesale and sales tax
exempt inquiries to:
RITRONICS WHOLESALE,
56 Renver Rd. Clayton_
Ph_ (03) 543 2166 (3 lines)
Errors and omissions excepted.
Prices and specifications subject
to change.
:~~!a~SApple
~T;n~i~a~~~~~~s
Machines. •
is a registered trademark.
' Oenotl:S registered !racfmarks ol their
respeclrve owners
RELICS OF A BYGONE ERA - SANTA FE's 2900 class steam locomotives used 2-metre high driving wheels to achieve
express speeds and pulled a huge tender that carried 32 tonnes of fuel and 120 tonnes of water. Despite their low
running costs, nothing could stop the trend to diesel-electric locos and the Santa Fe steam era ended in 1959.
trend coming. And they all found
that tradition means little in competitive business. Three newcomers
to the loco building business had
appeared on the American scene.
Electromotive Division (EMD)
The General Motors Corporation
in 1941 established their Electromotive Division which soon
became known to the world as
EMD, maker today of most diesel
electric locomotives (89 % of
American production one year).
Even when manufacturers outside
the USA produce locos, often the
diesel engine used is an EMD
product.
In 1942 EMD unveiled to the
world their new philosophy railroads would find it cheaper to
purchase EMD diesel electric
locomotives ready made "off the
showroom floor" and couple as
many as needed together for each
haulage task.
Revolutionary thinking indeed!
And it took some years for the
railroads to see this new wisdom.
Eventually they did.
Any number of smaller diesel
electric locomotives could be coupled together and controlled in unison
by one driver with one motor controller situated at the head end.
If a railroad needed 6000hp
(4.5MW), simply sell them six
82
SILICON CHIP
lO00hp (746kW) locomotives or
four 1500hp (1.12MW) units and let
the user couple them all together.
For loads up to about 25,000 tonnes, the very large couplings and
drawbar systems already in use in
the USA would allow an incredible
number of diesel electric locomotives to be coupled together at
the head end.
In America six locos coupled
.together is a common sight with up
to twelve being occasionally used in
mountain regions where long
cork-screw tunnels inhibit the use
of radio controlled locos in midtrain.
This "multiple coupled locomotive" philosophy was expounded
by the EMD salesmen, pushing the
belief that no longer was it
necessary to custom-design locomotives for a particular rail-road.
General Electric, experienced in
electric locomotive production for
many years, had less trouble in turning to diesel electric manufacture
than did factories like Baldwin. The
latter had enormous investments in
plant tailored to steamer production, a dedication which severely
dented their fortunes. A worse
mistake was its failure to see that
railroads no longer needed single
huge locomotives.
Traditionally the big three had
custom built large steam locos to
the requirements of each railroad.
They even designed locomotives
specifically for one mountain section of line. Don't laugh, Australian
railways did likewise.
For example, the NSW 57-class
steam locomotive was designed
specifically to conquer the Blue
Mountain section from Emu Plains
to Lithgow. So specific was that
design that the 57-class could not
run on the northern line of NSW.
The wide firebox and ashpan of the
5 7-class would not pass through
platforms of stations to the north of
Hornsby. So the idea of "general
purpose" locomotives took some
getting used to.
While the big three did eventually enter diesel electric locomotive
production, they had to contend
with EMD as well as the other two
innovative newcomers. For a while
the innovations challenged EMD's
"stock line" philosophy. But that
story we leave till next month. l!tl
Subscribers
Are you about to change your address? Please advise us by the
middle of the month to ensure
that your next issue arrives at
your new address.
Don't miss a
single issue
j .Electronic
t h.ouse number
J
? Convert a CB radio
IF YOU'RE THE KIND OF READER that can't
wait to get the next copy of SILICON CHIP, then
why not have the magazine delivered direct to
your door? Each month, we'll bring you the best
and brightest electronics magazine in the
business, put together by Australia's most experienced team.
*
l for amateur use
I'
1
5-element
· FM antenna
Hili review;
Yamaha's brilliant
new CD player
Constructional Projects
for the Enthusiast
*
Amateur Radio by
Garry Cratt
*
*
*
The Serviceman's Log
Plus - the Original & Best iv Servicoman,. v·inl~g♦
Radio, The Way l Se& It, the Evolut ion of Electric
Railwayio;
·· ·
fOd
"bscr·b
• e
a
bi, fill;
JtJa;,- 119
JI
0
s111> ,,.,, th. 11t a,.d
The Way I See It
Sc,-•
1PtioIS
11
Hifi Features & Reviews
Collp
o,.
FREEPOST * SUBSCRIPTION COUPON
□
New subscription
□
Renewal
Start in _ _ _ _ _ __
Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
(PLEASE PRINT)
Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Suburb/tow ~ - - - - - - - - - - - Postcode_ _ __
1 year (12 issues)
□ $A42
2 years (24 issues)
□ $A84
NZ & PNG (airmail)
0 $A65
□ $A130
Overseas surface mail
D $A62
Overseas airmail
□ $A120
D $A130
D $A240
Australia
Enclosed is my cheque/money order for $ _ _ _ or please debit my
□ Bankcard
Card No . I
□ Visa Card
I I I I I I I I I I I I I I I
I
Signature _ _ _ _ __ _ _ Card expiry date_/_/__
Subscription
Hotline
We can accept your subscription order by telephone. Just
ring us on (02) 982 3935 and
quote your Bankcard or Visa
Card number and the expiry
date.
Detach and mail to:
FREEPOST 25
SILICON CHIP PUBLICATIONS
PO BOX 139
COLLAROY BEACH
NSW 2097
• No postage stamp
required in Australia.
W
dftJ
I
L-------------------------------------~
DECEMBER 1988
83
I PRODUCT SHOWCASE I
is 40 amps into 20 loads. This has
been obtained by using eight Mosfet
power transistors in each channel.
The all metal cabinet has been
designed for installation in standard rack systems and the circuit
features comprehensive protection
against overloads and excessive
temperature. A variable speed fan
is fitted for cool and quiet
operation.
For further information, contact
the Australian distributors for Ortofon products, Scan Audio Pty Ltd,
PO Box 242, Hawthorn, Victoria
3122. Phone (03) 429 2199.
Ortofon's first
power amplifier
Having recently celebrated 70
years as a manufacturer and 40
years since it made the first moving
coil cartridge, Ortofon has just
released its first power amplifier,
the PPA 600. This unusually styled
unit has a rated power of 225 watts
per channel into 8 ohm loads and
350 watts per channel into 4 ohm
loads. Rated harmonic distortion is
less than 0.1 % .
According to Ortofon, the PP A
600 is intended for demanding professional and audiophile applications. It can be used in two channel
mode or, for higher power output, it
can be connected in bridged mode
to act as a mono amplifier. In this
configuration it can deliver up to
650 watts into 80 loads and 950
watts into 40.
Claimed peak current capability
New logic probe
& logic pulsar
The Ultron UT1000 logic probe
and UT2000 logic pulser have
recently been released by IRH
Components at a very good price.
The logic probe has a response
to 50MHz and will detect pulses
with a duration of only 10
nanoseconds. It has pulse latching (memory), a CMOS/TTL
switch, and light emitting diodes
to indicate under and overvoltage as well as pulse and logic
high and low. Recommended selling price is $32 plus 20% sales
tax where applicable.
The UT2000 logic pulser has
an adjustable pulse rate from
0.5Hz to 500Hz and automatic
polarity. Maximum output is
84
SILICON CHIP
1000mA with low duty cycles
pulses. It can be externally triggered too and has output voltage
protection. Recommended selling
price is $32 plus 20% sales tax.
Both logic probes and pulsers
are widely available from
dealers or from IRH Components
Pty Ltd, 32 Parramatta Road,
Lidcombe NSW 2208. Phone (02)
648 5455.
Comprehensive
screwdriver kit
Our article on screws and
screwdrivers published last month
has already caused a great deal of
interest. Just. after we had completed the work on that article
Jaycar Electronics released this
handy 30 piece screwdriver kit.
Essentially the kit is a 215mm
long screwdriver with chromevanadium shaft and hex socket to
take interchangeable bits. The
hardened steel bits are held in
place with a magnet inside the hex
socket.
There are 26 screw bits comprising five standard flat bits, four
square drives, six Torx bits (T10,
T15, T20, T25, T30 and T40), two
Pozidriv (1 and 2 point), four
Phillips head (0, 1, 2 and 4 point)
and five Hex (Allen) bits. The only
one which you're likely to miss is
the Tri-Wing which can be picked
wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS
WOOD FOR CHIPS ... WOOD FOR CHIPS ... WO OD FOR C
Check Your Instrument needs in our NEW Price List
See Electronics Australia December or call tor a copy
20MHz GOS-522 popular
Features
low cost scope
• Sensitivity : 5mV/div to 5V/div
• Bandwidth : de to 20MHz.
• Timebase : 20nS/div to 0.5s/div
Teat lnatrument.
20MHz GOS-523 with delay and alternate trigger mode
Logic Probes & Pul•ro
ELP-800
Logic Probe Willuzzer
ELP-810
Loge Puser
41.115
41.115
Multimelert • Analogue
ST-350
Electricians Tester
33.60
Multimelel'1- Digi!al
DIGICOM-121 1 Universal Multimeler
85.00
Features
• Sensitivity : 5mV/div to 5V/div
• Bandwidth : de to 20MHz
• Timebase A : 20ns/div to 0.5s/div (Main)
• Timebase B : 20ns/div to 0.5ms/div (Delayed)
40MHz GOS-543 top of the line
~
i5
Q:
0
I.I..
Cl
0
~
EM'TEK
EDM-55
EDM-72B
EDM•1105A
EDM·1116A
EDM-1122
EDM-1135
EDM-1346A
EDM-21 16
FLUKE
FLUKE-23
FLUKE-73
FLUKE- 75
FLUKE-77
Pen Type DMM
3 1/2 Dg\ROlary Swch
31/2Dgl+ TransTsr
3 1/2 Dgl+Cap.Trans
3 1/2 Dg\9 Faitn
31/2 Dg\7Fcntn
41/2Dg\TrueRMS
31/2 Dgl Booch Mb'
AUIO!anging,Sealed
Multimeler
Multimeter
Multimeter
79.35
6S.10
87.85
130.35
147.00
132.05
223.00
301.70
362.25
192.00
~S.00
• Max sensitivity : 1mV/div
Features
• Modes : Ch1, Ch2 , Dual, Ch1±Ch2,
• Sensitivity : 5mV/div to 5V/div
X-Y
• Bandwidth : de to 40MHz
• Swee : Auto , Normal, Sin le
• Timebase A : 20ns/div to 0.5s/div (Main)
• Timebase B : 20ns/div to 0.5ms/div (Delayed)
a
Function Generator GFG-8019
a
• Multi-Function with BUILT-IN 10MHz Counter
• AM, FM Modulation internal or external
• Auto/Manua l Sweep
• 0.2Hz to 2MHz Frequency Range
• Sine, Triangle, Square, Pulse and
Ramp Waveforms
• >20Vp-p open Circuit output, 1OVp-p
into 50Q
• Variable duty cycle and de offset
• VCF gives 1000:1 frequency ratio for 0-1 OV input
ri
-,,
))
l:
~
Frequency Counter GFC 801 OF
• Frequency Range from 1Hz to 120MHz
• Sensitivity <20mV, 10 to 100MHz,
<30mV 100MHz to 120MHz
339.00
V
'
200
I
JOO
~
• 100
,<-3. .
Frequency Coun1e<1
GFC-801 OF
Frequency Count,.
GFC-8055F
Frequency Counler
GFC-8100F
Frequency Counter
I "" . __,
l ~ ~-:
GOLDSTAR
DM-6135
DM-6235
DM-6335
355.25
572.75
355.25
Function Generalors
GFG-2D
Fctn Gen .2Hz-2MHz 468.60
GFG-8019
Fen! Gen .2Hz·2MHZ 643.80
GOLDSTAR 3 1/2 Dgl
DM-6135+ Mem & Hold
DM-6235 + Data Hdd
~
C)
Oscinoacopea
20MHz Osciloscope 910.00
GOS-522
88.80 GOS-523
20MHz Scope W/Dly 1210.55
40MHz Osciloscope 1493.30
99.60 GOS-543
118.80
4
(,
a
C)
-,,
a
~
CiampMete<t
DCP-9
Clamp Meler
MCP-4
Clamp Meter
POWER SU PPLYT corn Po,ver Supply
TA-1
Temperature Prooe
155.00 Panel Melen
88.85 ST-38-lOA-AC 45x45mm AC Pnt Mr
20.00 ST•38· 10V-DC 45x45mm DC Pnl Mr
55.96 ST-38-30V-DC 45,45mm DC Pnl Mr
ST-45-lOA·AC 51 x5 1mm AC Pri Mr
ST-45 -50/SOuA-DC 51x51mm DC Pnl Mtr
Test lnab'umenl Acceasorie•
CC6000
GOLDST AR Solt Case 13.80 ST-45-lOV-DC 51x51mm DC Pn! Mr
49.50
ST-45-lOOuA-DC
51x51mm DC Pnl Mr
COLINE-TEST-LEAD CAO Probes,Swtctlll
24.65 ST-45-lOV -DC 51,51mm DC Pnl Mr
DC-1
Scope Dust Cover
12.40 ST -65-lOA-AC 67x67mm AC Pri Mr
. ESCORT-CASE-EC30 Solt Meter Cases
42.55 ·1 ST-65-30A-AC 67,67mm AC Pnl Mr
1 FLUKE-CASE.C25
FLUKE Case
25.30 ST-65-1,00/lOOUAD 67x67mm DC Pnt Mn
FLUKE-HOLSTER
FLUKE Hlsb' Mdl 70
67x67mm DC Pnl Mb'
! FLUKE-Y8134
FLUKE Test Lead Set 55.20 ST-65-lA -DC
1
ST-65-5A-DC
67x67mm DC Pnl Mtt
))
ri
15.30
15.30
15.30
15.55
15.55
15.55
15.55
15.55
19.50
19.50
19.50
1950
19.50
l:
~
~a
C)
-,,
a
))
ri
l:
'ti
Cl)
~
GEOFF WOOD ELECTRONICS PTY LTD
a
229 Burns Bay Road, (Corner Beatrice St.) INC IN Nsw
Lane Cove West, N.S.W. P.O. Box 671 , Lane Cove N.S.W. 2066
a
Telephone: (02) 4271676, Fax: (02) 428 5198.
ri
8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday.
Mail Orders add $_5.00 to cover postal charges.
Next day delivery in Sydney add $5.00.
~
All prices INCLUDE sales tax.
Tax exemption certificates accepted if line value exceeds $10.00.
BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED
C)
-,,
))
l:
up from specialist tool suppliers.
Also included is a 1/4-inch socket
adapter and a 1/4-inch socket to
hex adapter. The whole kit is housed in a red plastic case. A handy
feature of the screwdriver is that
you can store a number of bits in
the handle.
Available from all Jaycar Electronics stores and dealers, the kit is
priced at a bargain $19.95. Get in
and get one today.
Electronic tyre
pressure gauge
Tyre pressure gauges in service
stations are notoriously unreliable
and often pocket tyre gauges are
not much better; a tolerance of
± 10% is probably the best you can
expect. For those that want more
precision, this electronic tyre gauge
is the answer.
Made by Sensym of the USA, it
has a liquid crystal display and will
measure tyre pressures from 1 to
127 psi with an accuracy of ± 1
psi. When you turn it on, by pushing
a red button on the side, it
automatically calibrates to zero. It
has a microprocessor and operates
on three 1.5V button cells
(Eveready S13E or Duracell MS13)
which are supplied at purchase.
After taking a measurement the
reading is retained for about 20
seconds and then it turns itself off.
We found the unit works well
although if you take a measurement
with your right hand, the LCD
readout is upside down when you
take the gauge off the tyre valve to
read the pressure. Apart from that
small quibble, it is a very good tyre
gauge. It sells for $65.20 including
sales tax.
For further information, contact
NSD Australia, Unit 3, 12 Victoria
Street, Lidcombe, NSW 2141.
Phone (02) 646 5255.
"Sensational Price Offer''
Co NTAc T
CONTACT
CONTACT
ELECTRONIC PARTS
COMPUTER SPECIALS
COMPUTER SPECIALS
■
PLUGS, SOCKETS & SHELLS
a:
Ill
DB 19
DB 23
DB 25
PLUG SOLDER
PLUG SOLDER
PLUG SOLDER
2.79
2.20
0.70
DISK SlORAGE BOX 100 x 5 1/4"
DISK HOLDER FOR'10 ~ 5 1/4'
COPYHOLDER DESKlOP ADJ/ ARM
9.00
2.75
23.00
DB 19
DB 23
DB 25
SOCKET SOLDER
SOCKET SOLDER
SOCKET SOLDER
3.65
2.95
0 .70
IBM AT /XT JOYSTICK
ATARI CHALLENGER JOYSTICK
19.00
10.00
DB 19
DB 23
DB 25
BACK SHELL
BACK SHELL
BACKSEHLL
1.45
1.35
0.60
C-800 WITTY MOUSE
MAGIC M WITTY MOUSE
60.00
65.00
XT CASE & LOCK
AT CASE & LOCK
60.00
89.95
0
a:
0
_,
j
I
NICAD BATTERIES
a:
AAA 180 MAH
AA 500 MAH
C CELL 1.2 AH
D CELL 1.2 AH
D CELL 4 AH
9 VOLT
c
RED HOT SPECIALS
150
3.20
2.00
5.80
5.90
11.50
12.00
0_,
:I
D0342 MOUSE PAD
S0225 NUMERIC KEYPAD
C0085 ELECTRET MIC INSERT
6.00
2.95
0.45
COMPUTER BITS & PIECES
HAND SCANNER HS 2000
MONllOR STAND 12/14' + LOCK
KEYBOARD 101 KEY CLICK TYPE
SEAGATE HARD DRIVES W/O CONT
375.00
19.00
99.95
ADD ON CARDS
CGA SHORT
MONOCHROME + PRINTER
MULTI 1/0 + FDC
PRINTER CARD
RS232 SERIAL 1 PORT
POWER SUPPLIES
150 W
180 W
220 W lOWER
78.00
75.00
76.00
22.95
49.95
75.00
99.95
139.95
ST
ST
ST
ST
ST
225 20M 65MS
238 30M 65MS
251 40M 40MS
251-1 40M 26MS
277R 60M 40MS
350.00
430.00
790.00
1000.00
1000.00
GOLD PLATED HIGH QUALITY LEADS
PLUG 10 BNC PLUG
5.95
PLUG 10 RCA PLUG
5.50
PLUG 10 3.55mm PLUG
3.00
BNC
BNG
RCA
RCA
PLUG 10 RCA PLUG
3.50
PIONEER SPEAKERS
SPEAKER
SPEAKER
SPEAKER
SPEAKER
SPEAKER
SPEAKER
10'
10·
10·
12·
10·
12·
60W 8 Ohm
100W 8 Ohm
120W 8 Ohm
150W 8 Ohm
200W 8 Ohm
250W 8 Ohm
29.95
54.95
59.96
69.95
79.95
149.95
I,..
0
"
CII
!8
I
GOLD PLATED HIGH QUALITY LEADS
W0201 TV 10 TV GOLD 1.5M
W0200 TV 10 VIDEO GOLD 1.5M
W0202 VIDEO CABLE SET
3.50
3.50
9.95
Ir
0
"m
"
CII
ALL PRICES INCLUDE SALES TAX
JYHOLESALE ENQUIRES WELCOME
PRICES VALID WHILST STOCKS LAST
CONTACT INTERNATIONAL
Suite 2-283 Burbridge Road
Brooklyn Park
SOUTH AUSTRALIA 5032
PH . 08 ·231 -2202
Fax 08-352-1449
P.O. Box 390, Cowandil/a ,
South Australia 5033
················································································································
Mall Order
Postage
Less than $50 ....... ........................ $3.50
$50 - $99 ······································ $4.50
$100 - $250 ·································· $7.00
Above $250 ................................ $10.00
Heavy Items adds extra
• IBM is reg . trade mark of International Business Machines
• XT, AT and Atari are registered trade names
0
BANKCARD
O
MASTERCARD
O VISA
EXPIRY DATE
Card No ...... ..........................................
Signature: ......... ... ... .. ................ . .... ..... .... ... .................. .. . .
(Note: unsigned credtt card mall ordera cannot be accepted)
Name: ........................................................................... .
Address: ........................................................................ .
. .... •..... ... ..... ... ... ........ .... ... ............ Postcode: .................. .
(Please allow 14 DAYS for normal mall and bank clearance delays)
Anti-tinkle module
from Pre-Pak
New car stereo has
4-digit security code
Do you have a "tinkle" problem?
It is common in domestic installations where there is more than one
telephone. Even though the bell circuit is disconnected in one of the
phones it may still "tinkle" when
the other phone is dialled.
This problem can be solved in
4-wire installations by appropriate
wiring of both phones but this may
not be an option if one of the phones
is a two-wire model.
Enter the "anti-tinkle" module
which is a Telecom approved product. It is wired into the offending
phone's bell circuit according to the
supplied instructions. Presto, no
more tinkle.
Priced at $14.95, the anti-tinkle
module is available from Pre-Pak
Electronics, 27 Cowper Street,
Granville, NSW 2142. Phone (02)
569 9797.
Large range of
rotary switches
One of the problems with most
car radio tape players is their little teensy knobs and control
labelling. Even the dial is often
hard to read, especially in bright
sunlight.
This new model from Philips
tackles these problems. Called
the DC681, it has a large twocolour liquid crystal digital
readout with orange(!) night
lighting.
Instead of miniature knobs for
bass and treble controls, fader
and balance, the DC681 has four
buttons for these functions. You
press the button for the bass setting, for example, and then
rotate the large volume control to
give the required boost. Two
seconds later the volume control
rotary switches required in the high
performance AC Millivoltmeter
described in the August and
September issues, Danner Electronics should be able to help. They
are located at 51 Georges Crescent,
Georges Hall, NSW 2198. Phone
(02) 724 6982.
reverts to its normal function.
All the settings are stored in
memory along with the preset
FM and AM stations. The
memory retains all the stored information even if the car's battery is disconnected. However, if
the DC681 is stolen it will not
work unless its 4-digit security
code is entered in via its
pushbuttons.
The tape player features
music search, Dolby noise reduction and standby mode which
allows radio reception while the
cassette remains in the deck.
This stops entry of dust and rattles which can happen with a
partly ejected tape. The unit also
switches automatically to radio
during fast winding. Power output is quoted as 2 x 20 watts.
For further information, see
your car stereo dealer.
Voracious cable
chomper from Arista
Electronics store
at Engadine
No that switch is not being held
by a miniature hand - it is a very
large rotary 2-pole 6-position
switch. It and a large range of more
normal rotary switches in sealed,
multiwafer and miniature styles
are available from Dauner Electronics.
If you are looking for the special
A new electronics store is now
open at Engadine.
To be known as Engadine Electronics and Communications and
situated at 1/10 Waratah Road,
Engadine, the new store will have a
wide range of electronic componentry on sale. As well, the new firm
will be service agents for Sharp
equipment, including marine
radios. They will also be selling and
installing cellular phones. Their
phone number is (02) 520 7495.
You had better have plenty of
cable around if you buy this
voracious cable chomper. It is so
comfortable and effective to use
you'll find yourself chopping
through cables for the heck of it. It
goes through 3-core mains cables
and shielded cables without turning
a (metaphorical) hair. It is availabie
from all Arista sales outlets at
$59.95.
DECEMBER 1988
87
Something to build over the
break . .
What break, you say! OK - why not take advantage of the
couple of days off to build yourself a great kit. Like these
superb hi fi speakers, for instance:
BONUS!
Build yourself a doorbell and we'll throw in
an extra 8 Xmas
tunes: FREE!
Comract Book
shel System
Put them together in a
night or so - and you 'll
have a great pair of
speakers rated at approx.
40 watts cont (100W
max). All you need is
some glue, a screwdriver
and a bit of time.
t~r;i_tive woodgrain type
You'll ,need:
An enclosure pack
50
(K-4000)
Two Woofers (K-3998)
Two Tweeters (K-3999)
S212
559 50
s13so
Normally great
value at s249
THIS MONTH ONLY s229
More great kit savings . . .
Home Alarm
Build your own alarm controller
and really save - AND - - - - ,,o...._
only you will know
the particular system you ve built. It's easily ......_
good as most
commercial
alarms, too!
Cat K-3424
Normally $149.00
THIS MONTH:
s99
Optical Motion
Detector
Nifty little idea for
security alarms, etc.
Photosensitive IC
senses chang es in
light level when
someone walks in
front of it. Neat - but
effective! Cat K-2721
Normally $27 .95
THIS MONTH:
5
1995
Walkabout Wadio
Why build yourself an AM radio when you can
buy one - possibly even cheaper. Just for the fu n
of it! PS - Betcha this
beats the pants off one Normally $19.95
you 'd buy!
ges
cat K-2720
THIS MONTH: S
What a great bargain: just in time
for the festive season! You can
build this superb new musical
doorbell, with 16 popular
evergreen tunes, and we'll also
include FREE a second tune chip
with 8 extra Christmas tunes and
Carols! What a fantastic project to
build -and now you 'll really
impress the friends and rels this
Christmas!
16 Tune
"Standard"
Repertoire
• Twinkle Twinkle • Eency Weency
Spider • Santa Lucia • Are You
Sleeping • London Bridge
• Butterfly • Coo Coo Waltz (2)
• The train is runn ing • Coo Coo
Waltz (1) • Lullaby • Clementine •
Rocka-a-bye-baby • Little brown
jug • Long Long Ago • Mary had a
little Lamb • Dream of Home and
Mother Cat K-2726
r.
Masthead Amplifier
Bonus Xmas
Tunes!
• Jingle Bells• Santa Claus is
Coming to Town • Silent Night
• Rudolph the Red Nose Reinder
• Joy to the World • We wish you
a Merry Christmas • O Come all
ye Faithful • Hark the Herald
Angels Sing
This chip normally $10
extra: This month FREEi
NORMALLY
THIS
MONTH
Crook TV signal? Build your own masthead
amplifier and fix it! Very simple to build,
comes complete with all hard ware, power
suppl y, etc. Easy one night project. Cat K-5 800
Multi-Purpose Pre-Amp
Here's versatility! EA's ingenious new pcb is adaptable to just about any
preamp - or the power supply for same. Whatever you want in audio
preamps - you 've got! Short form kit - incl udes pcb, op-amp etc; you supply
passive components depending on type of preamp you want. Cat K-5010
sggs
Proximity/Motion Detector
Another new one from AEM. It's an oscillator which reacts to bodies (yours,
anyones!) -up to 20 metres away. Adjustable sensiti vity down to
95
centimetres. Think of the applications! Cat K-8100
sa&
$49.95
$3995
Remote Switch Transm1
A really worthwhile add-on to for car alarms, etc etc.
Suits the devices recently described in Silicon Chip this kit is for the tran smitter only. (EGa spare, one
for your partner, etc etc). Cat K-8150
s1sss
TELETEXT
for your existing TV set!
• Not a kit - it's ready built
and tested. Just plug it in!
• Uses your VCR tuner to save
you$$$.
• Hundreds of pages of the
latest news, sport, finance,
weather, information ... all
free!
• Also receives "subtitles" or
closed captions for hearing
impaired.
• Easy to use!
• Designed and manufactured
in Australia, with full service
back-up through Dick Smith
Electronics.
• Infra-red remote control
INCLUDED at no extra
charge!
WHY BUY A
NEW$1100
TELETEXT TV?
ONLY
$
5 79
At last! Now you can receive Teletext - without going to the
huge expense of buying a new Teletext TV!
Haven't seen Teletext yet? You're missing out on the latest
news, stock exchange and financial information, sport results and
TAB information, weather reports and forecasts, even
recipes, jokes and much, much more. It comes to you
absolutely FREE - courtesy of the Australian Television
Network.
On a normal TV, it's the little colour flashes you see in the
black bars between picture frames when your TV "rolls". Unless
you have a Teletext TV or decoder, you don't even know
they're there!
And don't forget, most stations transmit popular programmes
with subtitles for the hearing impaired. This Teletext decoder will
let you see subtitles too!
Until now, you've had to buy a specially equipped TV to
receive Teletext.
Now you can buy just the Teletext decoder - and keep your TV
set!
It's not a kit - it's ready to go. And because it plugs into your
video cassette recorder, costly duplication of the tuner section is
eliminated. So you save!
Isn't it time you had the benefit of Teletext in your home?
Cat L-4468
ONLY AVAILABLE
FROM
ASK SIUCON CHIP
Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line
and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097.
Walkaround throttle
makes locos noisy
I have built the Walkaround
Throttle described in the May and
June issues and there is one problem I can't solve.
I am running N-scale locomotives
with conventional motors; ie, 3 or
5-pole armatures. When used with
the above controller the motors
emit an audible hum when running
and when stationary (under or
below motor starting voltage). The
hum disappears at zero output from
the controller.
I have substituted capacitor
values as suggested to alter the
pulse rate, with the result that the
audio tone changes. I have exchanged all on-board chips but this
has had no effect.
Could this be related to transistor
switching noise? Were there any
Notes and Errata that I missed? Is a
major re-design needed for use with
N-scale? I have tried my locos on
pure DC and they emit no hum but
of course the excellent low-speed
starting and running with your
design is not possible with pure DC.
(R. B., West Richmond, SA).
• As we noted on page 38 of the
April issue, motor noise can be a
problem, particularly at the lower
speeds permitted by the controller.
It is caused by the transistors
rapidly switching on and off the
voltage to the loco motor. By varying the duty cycle of the switching
(ie, the ratio of the "on" time to the
"off" time), the power to the motor
is controlled.
There is essentially nothing you
can do to the circuit to reduce the
noise produced by the motors. Your
Queries on the Studio 200 preamp
I have been reading about
your Studio 200 Control Unit and
plan to build one but I have some
comments and queries.
You mentioned that when
headphones are in use, the signal
connection between the control
unit and power amplifier is
broken to reduce distortion.
However, you seem to have
forgotten this at the inputs.
There is a line to TAPE OUT via a
lkO resistor. Now if the tape
player is off, wouldn't this cause
distortion in the same way?
Perhaps the lkO resistor should
be replaced by a buffer stage?
Regarding the earth wiring,
why not join all input earths
together and run one wire back
to the OV line on the power supply? Then there is no need for the
earth wires on all inputs (except
phono) to be connected to the Input/RIAA board. Furthermore,
the coaxial interconnections
need only to have the screen con90
SILICON CHIP
nected at one end only. Also all
power lines should run direct
between the power supply
board.
• As noted in the article in the
June issue, the main reason for
disconnecting the signal to the
power amplifier when headphones are in use is to avoid
blasting the speakers. Depending
on the configuration of the power
amplifier's input stages, unenergised transistors can cause
distortion.
In our experience, the same
problem does not occur with tape
decks which normally also have
a much higher input impedance
than power amplifiers.
The earthing arrangement in
the Studio 200 preamplifier and
power amplifier has been devised to minimise common mode
signal paths. If you alter the wiring layout, you run the risk that
the control unit will be noisy or
unstable.
unit is working exactly as it is supposed to. However, we wonder if
your layout is built on a very thin
baseboard. This will tend to amplify
any noise produced by the loco
motors. We have found that with a
"quiet" baseboard, motor noise is
not a big problem.
As a final thought, you could try
reducing the voltage from the
power supply. If your power
transformer has a 9 or 10-volt tap
use that instead of the suggested 12
to 15 volts AC. This will have the effect of reducing the unregulated DC
supply to around 14 volts. This will
mean a longer duty cycle pulse for a
given speed setting and may lead to
reduced noise from your loco
motors.
Query on
masthead amplifier
Congratulations to all at SILICON
CHIP. I have read this magazine
since issue one. In the Masthead
Amplifier published in the July 1988
issue, is the RF choke 11 a specialised component or is it an easily obtainable item? If not, can a
substitute be fabricated and what
materials are required?
I hope you can help with the
answers to these questions. Keep
the great stuff coming. (N. W.,
North Geelong, Vic).
• The RF choke in the masthead
amplifier is not a critical component. According to Philips data on
the OM350, the output RF choke
should be 5 microhenries or more.
You can make one by winding 27
turns of 0.3mm enamelled copper
wire on a short length of 1.6mm
diameter ferrite rod.
Solution to
tape player problem
I am writing in response to R. P.'s
problem with an indecisive cassette
player. Here is an explanation of
the cause of the problem.
50V source for
Speakerphone
testing
In your excellent article on the
Speakerphone, published in the
September issue, you mention a
test procedure involving a power
supply of between 25 and 50
volts DC. Now that's all very well
for these well equipped bods but
I don't have such a thing.
The closest thing I have to any
sort of a power supply is a 12V
battery charger. How do I go
about getting 50 volts DC without
having to spend a mint? (P. B.,
Emu Plains, NSW).
• Hmm. Well, you may not
think so, but you do have part of
the makings of a 50V power supply. For example, if you connect
a lOOOµF capacitor rated at
25VW (VW stands for "volts
working" by the way) or more
across the output of your battery
charger, you will find that you
now have a DC power supply
which puts out about 24 to 25
volts, with no load connected.
That's half way to your 50
volts and you've probably not
laid out any money yet if you had
the capacitor in your junk box.
Fig .1 shows how to connect the
capacitor to your battery
charger.
How do you get the remaining
25 or so volts? Easy. Just connect
three 9V batteries in series, as
shown in Fig.2. That'll give you
between 27 and 30 volts or more,
depending on how fresh the batteries are.
Now connect those three batteries in series with the battery
In auto reverse cassette players
one of the reels has a tape movement sensor which generates
pulses while ever the tape is moving. When the player comes to the
end of the tape, the pulses cease
and an electronic circuit operates
the direction changing solenoid.
The player then automatically
begins to play the other side of the
tape.
This circuit is essentially a
Fig.1: by connecting a lO00µF capacitor across a typical 12V battery
charger you can get about 24-25V DC.
9V
9V
9V
Fig.2: three fresh 9V batteries in series will give you 27-30V DC off
load. This can be connected in series with the output of Fig.1 to give
over 50V.
charger supply and you'll have a
total supply voltage of just over
50 volts. To achieve this, connect
the negative output from the battery charger supply to the
positive output of your composite
2 7V battery. The resulting
"stacked" supply will be your
desired 50 volts or close to it.
Such a supply will only be
capable of delivering about 10 to
15 milliamps but that will be
quite adequate for testing the
Speakerphone, as outlined in our
September article.
On the other hand, your battery charger-cum-DC power sup-
"missing pulse detector" similar to
the "End of File Indicator" featured
in the February 1988 issue of this
magazine.
The sensor can be in the form of
two spring fingers rubbing against
a segmented disc, mounted under
one of the hubs, or a reed relay used with a circular magnet under
one of the hubs.
Some small personal cassette
players use an optical system with
ply should be capable of delivering one amp or more before the
output voltage drops too much.
This can be quite handy as a
substitute for a proper power
supply.
Oh, and you don't really need
a battery charger at all, to get
50V DC. Just connect 5 9V batteries in series. That will give
you close to 50V straight away.
That'll set you back about $8 or
so, including the battery snap
connectors. And remember, you
don't need 50 volts anyway.
Anything over about 25 volts will
do.
an infrared LED being shone on an
optically segmented disc, with a
phototransistor creating the pulses.
I would suggest that R. P. check
to see if any pulses are coming from
this sensor and if they are being
acted upon correctly by the rest of
the circuit.
I have seen one cassette player
that was acting in the same manner
as R. P.'s. It used plastic gears to
transfer motion from the motor to
DECEMBER
1988
91
Silicon Chip Back Issues
Issue Highlights
November 1987: Car Stereo in Your
Home; 1GHz Frequency Meter;
Capacitance Adapter for DMMs.
December 1987: 100W Power
Amplifier Module; Passive lnfrared
Sensor for Burglar Alarms; Universal
Speed Control and Lamp Dimmer;
24V to 12V DC Converter.
January 1988: ~ 1:1m1....tjowtie UHF
~•
ower Supp,_ ,.,.,-nc.-rrnger; Subcarrier
Adapter
M Tuners.
February 1988: 200 Watt Stereo
Power Amplifier; Deluxe Car Burglar
Alarm; End of File Indicator for
Modems; Simple Door Minder.
March 1988: Remote Switch for Car
Alarms; Telephone Line Grabber;
Low Cost Function Generator;
Endless Loop Tape Player.
April 1988: Walkaround Throttle for
Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger ;
Headphone Amplifier for CD Players.
May 1988: Optical Tachometer for
Aeromodellers; High Energy Ignition
for Cars; Ultrasonic Car Burglar
Alarm.
June 1988: Stereo Control Preamplifier; Breakerless Ignition For
Cars; Automatic Light Controller;
Mega-Fast Nicad Battery Charger.
July 1988: Fitting a Fuel Cut-Off
Solenoid; Booster for TV & FM
Signals; The Discolight Light Show.
August 1988: Plasma Display;
Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting
the Most Out of Nicad Batteries.
September 1988: Hands-Free
Speakerphone; Electronic Fish Bite
Detector; Switchmode Charger for
12V Gel Batteries; Vader Voice.
October 1988: Stereo FM Transmitter; High Performance FM Antenna;
Led-Light House Number; Matchbox
Crystal Set.
November 1988:
Amplifier Module;
Plasma Display; Car
How to Quieten the
Computer
120W PA
Poor Man 's
Safety Light;
Fan in Your
BACK ISSUES ORDER FORM
Please send me a back issue for:
D November 1987
D December 1987
D February 1 988
D March 1988
D August 1 988
D May 1988
D June 1988
D July 1988
D April 1988
D Sept.1988
□ October 1 988
□ November 1988
Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my D Bankcard
Card No
--L---"----'----'----'-----'---'----'-----'- - - - ' - ' - -' - -' - -- ' - -..,___,
.
I _
Signature _ _ _ _ _ _ _ _ _ Card expiry date_/_/_ _
Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
(PLEASE PRINT)
Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Suburb/tow .__ _ _ _ _ _ _ _ _ _ _ _ Postcode____
D Visa Card
Price: $A5.00 each (includes
postage). Overseas orders add
$A 1.00 per issue for postage.
NZ & PNG orders are sent by
air mail.
Detach and mail to:
SILICON CHIP PUBLICATIONS
PO BOX 139
COLLAROY BEACH
NSW 2097
~-------------------------------------J
92
SILICON CHIP
Protection for
60W loudspeaker
I am writing concerning the
Studio 200 power amplifier
described in the February issue
of SILICON CHIP. I have built this
unit and find it to be a great amp.
I have it connected to two sets of
loudspeakers, one pair rated at
150 watts each and one pair
rated at 60 watts each. I was
wondering if you could suggest a
circuit to protect the less powerful speakers, in case I accidentally raise the volume too high.
I realise that since the
amplifier is rated at 100 watts
per channel I should not be able
to blow the loudspeakers.
However, I would like to be certain that I do not cause damage
to them. Also, if I wished to have
the two speaker systems as local
and remote, would I just be able
to connect the output of the amp
modules to a 2-pole 3-position
rotary switch, so as to select bet-
the hubs. A piece of dirt had
become stuck in the teeth of one
gear so that it could not turn
completely.
As the gear turned it would jam
and stop the tape. This then caused
the motor to change direction
whereupon the gear would jam
again. Removing the obstruction
fixed the cassette player. (M. A.,
Gore Hill, NSW).
• Thanks, M. A. We have also
been told that intermittently jamming cassettes are often the cause of
problems with auto reverse tape
players, particularly those in cars.
Tapping the cassette housing will
often clear the problem for the time
being but the fault may strike again
some time later.
Sensitivity adjustment
on 1GHz DFM
I am having trouble adjusting the
sensitivity of my 1GHz Frequency
Counter (as described in the
November 1987 to January 1988
issues). At switch-on, the LED illuminates but will not change state
no matter what adjustments are
ween local, remote or both?
Last but not least, I would like
to congratulate you on the great
work you have put in to the
magazine. I have been reading it
since the second issue and I love
it. Keep up the good work. (T. I.,
Matraville, NSW).
• Your cautious approach to
speaker protection is a good one.
You have to bear in mind that the
100W modules in the Studio 200
can probably deliver 200 watts
or more when driven into clipping, before their associated PTC
thermistor acts to limit the
current.
The solution is quite simple
though. All you have to do is to
connect a PTC (positive temperature coefficient) thermistor of
appropriate rating in series with
the speakers you wish to protect.
As it happens, the thermistor
specified for the 50 watt
amplifier module described in
our December 1987 issue will be
made to VRl. Even tapping VRl
causes little disturbance to the
LED.
Also, the parts list and circuit
diagram both .call for 15 0.0lµF
miniature ceramic capacitors but
the parts overlay only shows 14.
What happened to the fifteenth? I
am hoping you can help me with
this problem. (G. W., Willmot,
NSW).
• As a first step in solving this
problem we suggest you check the
main counter board very carefully
for any board defects such as
solder bridges between tracks or
open-circuits in tracks. On this
closely packed board with its fine
tracks it is quite easy to miss a
defect. You need strong light and,
ideally, a magnifying glass.
Once you are sure that there are
no board defects, you can go on to
check the logic states of the 10116
triple line receiver; ie, the device
which drives the LED in question.
Since the 10116 is an ECL (emitter coupled logic) device, its logic
states are quite different to those
for the more common CMOS logic
devices. Instead of logic 1 being
just the ticket. It is a Raychem
type RDE 115 Polyswitch. It is a
stock item from Jaycar Electronics (Cat. No. RN-3415) at
$8.95 each. You will need one for
each 60 watt speaker box. We
suggest you install each Polyswitch inside the speaker box.
As far as a speaker selector
switch is concerned, your suggestion is workable although the
readily available rotary switches
from electronic parts retailers
do not really have rugged enough
contacts to carry the relatively
high currents involved. As a partial solution, we suggest that you
use a 4-pole 3-position switch,
and parallel the switch sections
so that you get a higher current
capability.
A better solution may be to use
a pair of mains-rated DPDT switches with 10-amp contacts. You
need one switch for each pair of
speakers. To select both speaker
systems, both switches should be
on.
close to + 5V and logic 0 being
close to 0V, the ECL logic 1 corresponds to - 0.9V below the + 5V
supply while ECL logic 0 is -1.75V
below + 5V.
This means that the pins on an
ECL device should be higher than
+ 4.1 V or lower than + 3.25V,
assuming that the 5V supply is exactly 5V.
So go through and check each of
the pins on the 10116. Pins 9 and 10
should be close to + 3. 7V, pins 1
and 16 should be at + 5V and pin 8
should be at 0V. All the other pins
should be at ECL logic levels.
Note also that since the 10116 is
a differential device (with differential inputs and outputs), its inputs
and outputs are complementary.
For example, if output pin 6 is high,
its complementary output at pin 7
will be low. Similarly, if output pin
3 is high, pin 2 will be low.
By checking the voltages right
around the device you should be
able to isolate the problem.
·
As far as the 15 .0lµF capacitors are concerned, the component
layout diagram is correct. There
are only 14.
DECEMBER1988
93
Index to Volume 1:
Nov. 1987 - Dec. 1988
Features
Electric Railways
11 /87 76 Your House Wiring Could Kill You
12/87 6 Using Your VCR to Tune UHF TV
Stations
12/87 40 Amateurs Link Coast to Coast
12/87 50 AT-Compatible Kit Computer
01 /88 12 The 1987 CESA Hifi Awards
01 /88 68 OTC's Automatic Seaphone
Service
02/88 6 Electronics and the Big Cat
02/88 1 4 Easy Tips on Headphone Repair
02/88 50 South Pacific: The Electronic
Version
03/88 6 New Life for Radio Cassette
Players
03/88 12 Vintage Radio: How It Began ,
Pt.1
04/88 6 Vintage Rad io: How it Began,
Pt.2
07/88 4 Amplifier Headroom: It It a Con?
09/88 8 Sony's Mind Blowing 8mm Video
Gear
10/88 4 Electronics & Brock's BMW
Blaster
11 /88 4 All About Screws & Screwdrivers
11 /88 8 Quieten the Fan in Your
Computer
11 /88 76 The Technology Letters, Pt.1
12/88 4 Electronics & Holden's V6 Engine
12/88 42 Kit Clinic
11 /87
Design & Theory
03/88 65 High, Low Sink & Source
Explained
04/88 10 What is Negative Feedback? Pt.1
05/88 42 Motorola's MC3334P Ignition IC
06/88 1 O What is Negative Feedback? Pt.2
07/88 50 National Semiconductor's LM833
Op Amp
07/88 70 What is Negative Feedback? Pt.3
08/88 54 A Look At Insulated Tab Triacs
09/88 58 Motorola's MC34018
Speakerphone IC
09/88 82 What is Negative Feedback? Pt.4
Digital Fundamentals
11 /87
12/87
01 /88
02/88
83
90
86
85
03/88 81
04/88 81
05/88 84
06/88 86
08/88 63
09/88 66
94
Lesson 1 : Binary Data
Lesson 2: Digital Logic Elements
Lesson 3 : Digital Circuits
Lesson 4: Understanding & Using
Flipflops
Lesson 5: Counters & Shift
Registers
Lesson 6: Combinational Logic
Circuits
Lesson 7 : Memory Circuits
Lesson 8: Introduction to
Microcomputers
Lesson 9 : Input & Output
Operations
Lesson 10: Programming
Microcomputers
SILICON CHIP
12/87
01 /88
02/88
03/88
04/88
05/88
06/88
07/88
08/88
09/88
10/88
11 /88
12/88
6 The Birth of Steam & Electric
Locos
68 Steam Locomotives Come of Age
4 The Problem of Braking
80 Australia's First 100 Years
76 Electrics in Australia
74 The Sydney & Blue Mountains
Systems
76 The First Electric Mainline
System
80 The First 3-Phase AC Electric
Railway
84 15kV 16.6Hz AC In Northern
Europe
76 Electrification in Central Europe
88 The Queensland 25kV Suburban
System
76 Queensland's Powerful New
Electric Locos
96 A Look At Diesel-Electric
Locomotives
76 Why Diesel-Electrics Killed Off
Steam
Vintage Radio
05/88
06/88
07/88
08/88
09/88
10/88
11 /88
12/88
6 Collecting Vintage Radio
Receivers
16 Cleaning Up the Chassis
10 Checking & Repairing the Valves
4 Capacitors Cause Lots of
Problems
4 Checking & Replacing Resistors
8 Checking Out the Power Supply
34 What To Do About the
Loudspeaker
14 Restoring the Dial Mechanism
The Way I See It
1 1/87 14 They'll Sell you Anything But
Don't Ask Them to Fix It
12/87 87 Is the Electronic Servicing
Industry Dragging Its Feet?
01 /88 82 Information Has Its Place But
What About Knowledge
02/88 70 Worth Preserving : A Colourful
Slice of Electronic History
03/88 72 The Quest for Ultimate Hifi is Half
the Fun
04/88 16 Audio Power Ratings - Right
Back Where We Started From
05/88 12 Is UHF TV as Good as It's
Cracked Up To Be?
06/88 6 For All Practical Purposes, Mr
Fixit Has Had His Day
07/88 18 Are Computers Turning Us Into
Automatons?
08/88 14 Some Things Are Enough to
Make a Grown Man Cry
09/88 22 Could We End Up Drinking Nickel
Cadmium Cocktails?
10/88 36 Fly By Wire: Is It Safe From
Electromagnetic Interference?
11 /88 28 Look Out TV Servicemen: VCRs
Are Now Disposable
12/88 44 UHF TV Problems in the lllawarra
Region
Serviceman's Log
11 /87
12/87
01 /88
02/88
03/88
04/88
46
73
56
60
50
54
05/88 56
06/88 38
07/88
08/88
09/88
10/88
34
28
38
44
11 /88 54
12/88 62
With Friend's Like That
All This In A Brand New Set
When The Chips Are Down
His Master's Voice
A Baffling Exercise
Beating An Intermittent When the
Heat's On
Double Or Quits - Toss Ya
Ring Out The New, Ring In The
Old
Sounding Out a Video Recorder
Sound Reasons For Confusion
Helping The Old Folk At Home
Curing Woolly Pictures At
Wollongong
My Friend (The Enemy) Flicker
The Customer Has No Idea
TETIA TV Tips
12/87 66 Rank Arena C2239 (82 Chassis)
01 /87 59 Blaupunkt (Bridge Rectifier
Chassis)
02/88 64 Sony KV1 800-AS
03/88 54 Thorn 9904 (Q Chassis)
04/88 55 Sony KV1 800-AS
05/88 60 Philips K9 Chassis
06/88 42 Rank Arena C2205
07/88 36 HMV 12613 (Braddon)
08/88 31 Philips (CA826) (Toshiba
Chassis)
09/88 44 General Electric TC53L2
10/88 49 National TC1401 A
11 /88 60 Sony KV1830AS (Early Version)
12/88 67 Kriesler 59-4/5/6
Telecommander Remote Control
12/88 67 AWA Thorn 3500 Series
Hifi Reviews
11 /87 11 Marantz PM-35 Integrated
Amplifier
12/87 17 Realistic Nova-1 5 Loudspeakers
01 /88 32 Marantz CD-94 Compact Disc
Player
02/88 30 Sony RA-N77ES Stereo Power
Amplifier & TA-E77ES Stereo
Control Amplifier
03/88 16 Tandy CD-1 500 CD Player
04/88 15 Arista CDS606 Compact
Loudspeaker System
06/88 15 Realistic Optimus 304
Loudspeaker System
07/88 .16 Amcron MA-1 200 Power
Amplifier
10/88 20 Yamaha CDX-1110 CD Player
12/88 18 Harman Kardon PM665Vxi
Stereo Amplifier
Circuit Notebook
11 /87 62 DC Speed Control For Model
Motors
11 /87 62 Measuring the Tracking of Dual
Potentiometers
Projects
11 /87 20 Capacitance Adaptor for DMMs
11/87 32 1GHz Digital Frequency Meter,
Pt.1
11/87 54 Car Stereo for Your Home
11/87 66 Off Hook Indicator for
Telephones
11/87 72 Portable Electronics Workbench
12/87 10 100 Watt Amplifier Module
12/87 28 24V to 12V Converter for Trucks
12/87 33 Passive lnfrared Movement
Detector
12/87 46 Speedi-Watt Lamp Dimmer
12/87 76 1GHz Digital Frequency Meter,
Pt.2
01/88 14 High-Performance UHF Antenna
01/88 24 Electronic Chime for Telephones
01/88 38 Dual Tracking ± 18.5V Power
Supply
01/88 48 1GHz Digital Frequency Meter,
Pt.3
01/88 64 Subcarrier Adaptor for FM Tuners
01/88 71 The Flexo Shortwave Antenna
02/88 18 Protector Car Burglar Alarm
02/88 36 Studio 200 Stereo Power
Amplifier
02/88 46 End-of-File Indicator for Modems
02/88 53 Build the Door Minder
02/88 56 Low Ohms Adaptor for
Multimeters
11 /87 63 How to Obtain -5V From A +5V
Supply
11 /87 63 Frequency Comparator With
Visual Display
12/87 18 Low Power RAM EPROM
Emulator
12/87 18 Simple Transistor Oscillator
12/87 19 Courtesy Light Delay Switch
12/87 19 Voltage Regulator For 1 2V
Alternators
01 / 88 22 Sequential Lamp Flasher For
Cars
01 /88 22 High Impedance Op Amp With
Input Protection
01 /88 23 Crowbar Over-Voltage Protection
For Power Supplies
01 /88 23 Substituting Electrolytic
Capacitors
02/88 34 Thermatic Fan Timer For Cars
02/88 34 Dynamic Noise Reduction For
Cassette Players
02/88 35 El Cheapo Car Burglar Alarm
03/88 38 Adjustable Load For Power
Supplies
03/88 38 Synchroscope For Frequency
Comparison
03/88 39 CAO Probe Modification
03/88 39 Precision Reset For
Microprocessors
04/88 50 High Speed Pulse Amplifier
04/88 50 Headphone Noise Monitor For
Power Amplifiers
04/88 51 Quiz Game Using a CMOS Latch
04/88 51 VU Meter For Tape Dubbing
05/88 50 Voltage & Current Metering For
Power Supplies
05/88 51 Improvements For Modem Endof-File Indicator
03/88 18 Line Grabber for Telephones
03/88 26 Remote Switch for Car Burglar
Alarms
03/88 40 Endless Loop Tape Player
03/88 43 Technilab 301 Function
Generator
03/88 56 Old-Time Crystal Radio
03/88 60 Build Your Own Light Box
04/88 28 Headphone Amplifier for CD
Players
04/88 32 Walkaround Throttle for Model
Railroads, Pt. 1
04/88 47 Build a Slave Flash Trigger
04/88 60 A pH Meter for Swimming Pools
05/88 18 Optical Tachometer for
Aeromodellers
05/88 32 High Energy Ignition for Cars
05/88 44 Walkaround Throttle for Model
Railroads, Pt.2
05/88 62 Ultrasonic Car Burglar Alarm
05/88 72 Build the Party Light
06/88 28 Studio 200 Stereo Control Unit,
Pt.1
06/88 44 Convert Your Car to Breakerless
Ignition
06/88 56 Automatic Light Controller
06/88 62 Mega-Fast Nicad .Battery Charger
07/88 14 Fuel Cut-Off Solenoid for Cars
07/88 30 Booster for TV & FM Signals
07/88 40 Studio 200 Stereo Control Unit,
Pt.2
07/88 56 The Discolight Light Show, Pt.1
07/88 74 Tone Burst Source for Amplifier
Testing
08/88 8 Build a Plasma Display
08/88 18 High Performance AC
Millivoltmeter, Pt.1
08/88 38 Universal Power Supply Board
08/88 42 The Discolight Light Show, Pt.2
08/88 56 Remote Controlled Chimes Unit
09/88 14 Hands-Free Speakerphone
09/88 30 Electronic Fish Bite Detector
09/88 46 High Performance AC
Millivoltmeter, Pt.2
09/88 60 the Incredible Vader Voice
10/88 14 FM Stereo Transmitter
10/88 28 High Performance FM Antenna
10/88 52 The Classic Matchbox Crystal
Set
10/88 64 The Led-Light House Number
11/88 14 High Power PA Amplifier Module
11/88 40 Poor Man's Plasma Display
11/88 64 Build a Car Safety Light
11/88 68 Add a Headset to the
Speakerphone
11/88 87 Dynamic Balancing for Electric
Fans
12/88 26 1 20 Watt Public Address
Amplifier
12/88 34 Car Antenna/Demister Adaptor
12/88 50 Diesel Sound Simulator for Model
Railroads
05/88 51 High-Q Notch Filter
06/88 69 Dual Power Circuit With Back-Up
Battery Indicator
06/88 69 Brighter Flashing Lamp For
Alarms
06/88 69 Flashing Pilot Lamp
07/88 14 Fuel Cut-Off Solenoid For Cars
08/88 34 Telephone Ring Simulator
08/88 34 DC Stereo Volume Control
08/88 35 Digital Lissajous Frequency
Comparator
09/88 34 National Semiconductor's LM12
150W Op Amp
10/88 70 Off Peak Indicator For Hot Water
Systems
10/88 70 Audio Overload Detector
10/88 71 Long Interval Timer
11 /88 32 Knightrider LED Scanner
11 /88 32 12-240V 60VA Inverter
12/88 59 Charger for 1 2V Gel Batteries
12/88 59 Constant Current Nicad Charger
04/88 67 Mobile Antenna For The VHF &
UHF Bands
05/88 70 Designing & Building Attenuators
06/88 72 Build An RF Sniffer Probe &
Preamplifier
07/88 64 A Look At Amplitude Companded
Sideband
08/88 84 How To Get The Most Out Of
Nicad Batteries
09/88 84 Switchmode Charger For Gel
Batteries
10/88 84 Convert a CB Radio to the
28MHz Amateur Band
11 /88 92 What's All This Talk About SINAD?
12/88 70 SSS Adaptor For Shortwave
Receivers
Safety Watch
03/88
03/88
03/88
10/88
71
71
71
71
VCRs & Water Don't Mix
Hazardous Power Cords
Safety With The Iron
Electric Shavers Should Be
Checked
Amateur Radio
Introducing Amateur Radio
Tuning In To The VHF Bands
Getting Started on Amateur TV
Line Isolation Unit for Phone
Patch Operation
03/88 68 Antennas For The VHF & UHF
Bands
11 /87
12/87
01 /88
02 /88
90
73
76
74
Notes & Errata
01 /88
03/88
03/88
06/88
06/88
95
96
96
95
95
07/88 95
08/88 95
08/88 95
08/88 95
08/88 95
09/88 103
10/88 99
10/88 99
11 /88 104
11 /88 104
11 /88 104
12/88 96
Digital Fundamentals
Capacitance Adaptor for DMMs
24V to 12V Converter
Remote Switch for Car Alarms
Passive lnfrared Movement
Detector
Remote Switch for Car Alarms
24V to 12V Converter
Protector Car Burglar Alarm
Optical Tachometer
Studio 200 Stereo Control Unit
UHF Remote Chime/Doorbell
Studio 200 Stereo Control Unit
Remote Switch & Remote
Chime
Low Ohms Tester for DMMs
Switchmode Battery Charger
Hands-Free Speakerphone
Stereo FM Transmitter
DECEMBER 1988
95
CEN
Cash in your surplus gear. Advertise it here in Silicon Chip.
CLASSIFIED ADVERTISING COUPON
Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents
for each additional word; Display ads (casual rate) - $20 per column centimetre (max.
10cm).
Closing date: five weeks prior to month of sale. If you use a PO Box number, you must
include your permanent address and phone number for our files. We cannot accept ads
submitted without this information.
To run your own classified ad, put one word on each of the lines below and send this form
with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097.
PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS
2
3
4
5
6
7
8
9
10
11
12
13
14
15 ($7.00)
16 ($7.40)
17 ($7.80)
18 ($8.20)
19 ($8.60)
20 ($9.00)
21 ($9.40)
22 ($9.80)
23 ($10.20)
24 ($10.60)
25 ($11 00)
26 ($11 .40)
27 ($11.80)
28 ($12.20)
29 ($12.60)
30 ($13.00)
Name ...
Address ...
Suburb/Town
Postcode .
Enclosed is my cneque or money order for $ ....... . .... . .... .. . ... .
D Bankcard D Visa Card
Card No
. or please debit my
!~~~-~~~~-~~~~~-~~~~~
Signature ........ .
FOR SALE
NEW 64K-256K PRINTER BUFFER
design release . VER 4.0 and REV G
boards now available. Double-sided
PCB, EPROM and instructions:
$39 .00 . Optional additions include 2 x
THE BUBBLE-ETCHER
Our Bubble-Etcher now has a
heater. Reheat the etchant when
you need it. Let the air bubbles do
the stirring. The perspex tank
forms a vertical slot. You see the
etching proceed. Suits boards up
to 1 2 x 1 0-inch. Ask us for a
pamphlet.
Sesame Electronics Pty Ltd, PO
Box 452, Prahan 3181. Phone
(03) 527 8807.
96
SILICON CHIP
Advertising Index
Allied Capacitors ...... ...... .... .. 21
Altronics ..... ..... ........ .... .. 38-41
Arista Electronics .............. ... 66
Avtek ... .... ..... ....... .... ... ...... IBC
Ballarat Electronic Supplies .. . 1 5
Bell lRH ... .... .. .. ............ ... ...... 9
Contact International .. ... .. ..... 86
David Reid Electronics ... ..... .. 33
Dick Smith Electronics ..... 12, 13
48,49,88,89
Electronic Solutions ...... .. 60,61
Geoff Wood Electronics .. ...... 85
Goldstar ..... .... ..... .. .. ... . : ..... IFC
Hycal Instruments ................ 1 5
Jaycar Electronics ... ....... 22-25
72-75
J.V. Tuners ............... .. ... ..... 67
Kenwood Australia .. ... .... ... OBC
Pre Pak Electronics ... ........ ... 69
RCS Radio .......... .... .. ... .. ... .. 4 7
Rod Irving Electronics ......... .. 81
Scan Audio .. .. ............ .. ....... 21
Sesame Electronics ....... ...... 96
7 -segment LED front panel display of
percentage full, 1 to 99 copies select,
3 polled computer inputs, printer switches, computer switches, and serial
converter boards. For a free catalog
send a 37c stamp to: Don McKenzie,
29 Ellesmere Crescent, Tullamarine
3043 .
RADIO/TV RESTORERS - We have a
large stock of new valves . Send SAE
for list or phone Shellharbour TV Service, 26B Mary St, Shellharbour,
2529. (042) 95 1175.
BOOKS & PLANS
LOW SPEED GENERATORS for windmills, water turbines, steam engines.
The definitive book: " The Homebuilt
Dynamo" (1987), 182 pages, 8.5" x
1 2", hardback. Generator design and
construction with ceramic magnets.
PC Boards
Printed circuit boards for SILICONCHIP projects are made by:
• RCS Radio Pty Ltd, 651
Forest Rd , Bexley, NSW 2207.
Phone (02) 587 3491.
• Jemal Products, 5 Forge St,
Welshpool, WA 6106. Phone
(09) 350 5555.
• Marday Services, 2139 Great
North Rd, Avondale , Auckland,
NZ. Phone 88 5730 .
Complete plans, 268 photographs,
step-by-step construction details.
$A85.00 postpaid airmail (brochure
$A5 .00 refundable). Todd-Forbes
Publishing, 627 West Coast Road,
Oratia, Auckland .
Notes & Errata
FM Stereo Transmitter, October
1988: the O.OlµF filter capacitor
connected to pin 12 of the IC should
be 0.00lµF. With the O.OlµF in
place the transmitter will not work
in stereo.
NOW SAVE EVEN MORE ON
THESE OUTSTANDING MODEMS
Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even
better value when you buy. Just check the features and the prices of Avtek and you'll see why it's the
modem chosen by more and more PC users.
More compact and
reliable than most and
suitable for data transfer
between PCs, on-line
services, E-mail and all
videotex facilities like
VIATEL (Model 123 only).
Available as a standalone
RS232 model or as a plug-in
true ½ card for IBM PCs
and compatibles.
Specifications:
Data Standards CCITTV.21 (300/300
baud full duplex).
Data rates - CCITTV.23
(1200/75 baud).
AN/DEAL
FIRST MODEM!
A fuly automatic operation,
HAYES-compatible smart modem.
Choose from 3 models (internal or external)
model 21/23 300/300, 1200/75
12
300/300, 1200/1200
123 300/300, 1200/1200, 1200/75
$
325
325
399
,~ID:llLlffill\l\\\.
A highly reliable data communicator at a budget
price. The compactly designed Minimodem II is
supplied complete with Telecom-approved, pushbutton phone.
PHONE NOW FOR FAST DELIVERY PH: (02) 888 5333
All Avtek modems are sold complete with power supply, instructions
and telephone connections. Designed and built in Australia, service
and technical support for modems is available direct from
Avtek Data communcations.
MAIL ORDERS WELCOME. AVTEK, P.O. BOX 651, LANE COVE 2066.
30-DAV. NO-QUESTIONS-ASKED, MONEY-BACK GUARANTEE.
~YTEK
DATA COMMUNICATIONS
(A Member of the NetComm Group of Companies)
L
SEND COUPON TODAY!
Name: _
_ _ _ _ _ _ _ _ _ __
Address: _ _ _ _ _ _ _ _ _ __ _
Name on Credit Card: _ _ _ _ _ _ __
Credit Card No: _ _ _ Expiry Date:_/_/_
Please rush me
Qty
Model
internal/external
price
Post to
Sub-total$
Avtek Data
Add freight$
Communications,
P.O. Box 651,
Lane Cove
TOTAL THIS ORDER$
2066.
10.00
AV005
|