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ASK SILICON CHIP
Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line
and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au
Advanced GPS
Computer cable length
I am thinking of building the
Advanced GPS Computer (June & July
2021; siliconchip.com.au/Series/366).
Could you advise whether a 2m
length of cable between the GPS module and the Micromite would be possible? I note that your photos only
show a cable approximately 50cm
long. I also wonder what sort of accuracy one can expect if the unit was in
a car doing, say, 100km/h. Keep up the
good work. (D. B. S., Artarmon, NSW)
• 2m is a bit long for a cable carrying TTL serial signals. It might or
might not work; it could be flaky. As
the GPS serial is usually only 9600
baud, you might get away with it.
Still, you would be better off using a
GPS module with an external antenna
socket, mounting it near the Advanced
GPS Computer and then running a 2m
shielded antenna cable to an appropriate antenna mount.
If you did want to extend the data
cable, we suggest you use a shielded
cable.
The speed accuracy is down to the
GPS module. The data for the VK2828
module we used suggests a speed error
of less than 0.1m/s (around 0.3km/h).
In our experience, the readings are
usually within 1km/h, with the update
lag introducing more noticeable errors
than the speed accuracy itself. That is
because many GPS modules only produce data once per second, plus there
is a processing delay.
GPS Computer
battery charging
I built the Advanced GPS Computer,
and everything seems to be working
OK, but the battery takes forever to
charge. Could I lower the value of the
10kW resistor between pin 5 of IC4
and ground to say 4.7kW? It will draw
an extra 100mA or so from the power
source, but I don’t see why that would
matter. (P. C., Balgal Beach, Qld)
• The battery we used in our prototype
siliconchip.com.au
did not have a specified maximum
charge current, hence the 100mA
setting, which is quite conservative.
Lower charging currents will be better
for long-term cell longevity too.
If you are confident that your battery
can handle a higher charging current,
then the 10kW PROG resistor can be
reduced as far as 2kW. That will give a
500mA nominal charge current, which
is the limit of the MCP73831 charge
controller IC. A 4.7kW resistor should
give around 212mA, as you suggest.
USB socket
part code query
What type of mini USB socket have
you used in the Battery Multi Logger
(February & March 2021; siliconchip.
com.au/Series/355)? The parts list only
describes it as an “SMD mini-USB
socket”. (B. C., Bray Park, Qld)
• We aren’t sure who originated this
design but it seems that virtually
everyone has copied it. While there
are surely incompatible SMD Mini
Type-B sockets available, many of the
parts you can find will fit this same
footprint. One part we know is suitable is the EDAC Inc. 690-005-299043, available from Digi-Key (Cat 1511206-1-ND) and Mouser (Cat 587-690005-299-043).
Substitute Mosfet for
Ultrasonic Cleaner
I’m thinking of building your High
Power Ultrasonic Cleaner (September & October 2020; siliconchip.com.
au/Series/350), but I’m finding most
suppliers of the SUP53P06-20 Mosfet
are out of stock.
Jaycar seems to still have a few (Cat
ZT2464), but if I can’t get those, can I
use the IPP80P03P4L-04 that you sell
in your Online Shop (siliconchip.
com.au/Shop/7/4318)? (E. Z., Turramurra, NSW)
• Yes, the IPP80P03P4L-04 should
be a suitable substitute for the
SUP53P06-20 in this circuit. It has
high enough current and voltage
Australia’s electronics magazine
ratings at 80A and 30V, and its gatesource voltage on-threshold is low
enough.
Short circuit on
Mini BackPack PCB
I built your D1 Mini BackPack with
WiFi (October 2020; siliconchip.com.
au/Article/14599) and was able to
load the demo software into it. When
I power it up, the screen for entering
a location appears on the LCD but the
touch function is not working. Can you
suggest a solution? (J. L., Tauranga, NZ)
• You most likely have a short circuit
somewhere on the SD card socket. The
SPI pins used to communicate with the
touch controller are also used for SD
card socket communications. As the
screen display is working, most likely,
the MISO line is shorted since that line
is necessary for the touch controller
to work but not the screen displays.
Have a close look at the pins on the
SD card socket and possibly remove
the SD socket if it looks as though
something could be shorting out
underneath.
The reader followed up to confirm
that this was the problem.
Reflow Oven wiring
diagram error
I’m building Phil Prosser’s DIY Solder Reflow Oven (April & May 2020;
siliconchip.com.au/Series/343). The
wiring diagram, Fig.11 on page 90 of
the May 2020 issue, shows the ribbon cable arrangement from CON8 to
the LCD module, but pin 1 of CON8
appears to go to pin 20 of the LCD.
The photo on page 89 appears correct, although I think the ribbon cable
cannot be folded neatly. Also, care
needs to be taken to prevent the LCD
Adaptor board from shorting out on
the display cover mounting clips. I’d
suggest some stand-offs or insulation
here. Could I have some clarification?
(I. T., Duncraig, WA)
• Phil Prosser responds: You are correct; Fig.11 shows the cable from the
August 2021 107
controller to the LCD with pins 1 &
20 swapped. The drawing probably
should have had pin 1 indicated on
the ribbon cable. I should have picked
that up. Yes, the photo is correct.
It is possible to fold ribbon cable to
‘neatly’ swap over the pins. It is a little
like origami, and it takes a little more
cable, but it does work. You need to
‘squish’ it pretty hard, but a clean bend
is possible. You bend the cable 90° in
the opposite direction you want the
corner to go in, then fold it back 180°
on top of itself.
This error was corrected in the
online version, with errata published
in the June 2021 issue of Silicon Chip.
We have not had trouble with the
LCD adaptor board, although thinking of the problem you describe, we
wonder if you are trying to mount the
adaptor close to flush with the LCD. We
generally use standard 2.54mm header
pins to connect the LCD adaptor board
to the screen, which gives 5mm+ of
separation between them.
Idea to help the hardof-hearing watch TV
Is there an unused audio channel
on the Australian TV broadcast standards? I have searched the internet for
an answer without success.
Recently, TV channels have been
broadcasting a secondary audio channel for the vision-impaired. I wonder
if another similar facility is vacant and
could be made available for the hearing impaired. Such an audio channel could exclude the background or
effects sounds that make it so difficult
for many hearing-impaired people to
understand TV dialog.
This would enable Australian programs such as current affairs to be
heard with ‘clean’ dialog. It seems that
once background and effects audio are
mixed in, there is no way of unscrambling the combination.
As an afterthought, is the primary
TV broadcast audio a multichannel
system so that viewers with 5.1 or 7.1
home theatre receivers can produce
this effect? If so, maybe a cooperative
TV broadcaster could have one audio
channel (perhaps the centre channel)
free of background/effects so that hardof-hearing viewers could connect to
that audio and hear ‘clean’ monaural dialog.
Some years ago, one of your readers
suggested changing the connections to
108
Silicon Chip
one ear of a pair of earphones (causing the ears to hear anti-phase) could
produce clean dialog, but I have had
no success with this. Any other suggestions would be most welcome. (B.
H., Cornubia, Qld)
• That is a great idea. While we don’t
have the technical details of the Australian TV broadcast standards, channels use either MPEG2/4 digital compression and encapsulation. MPEG2
supports up to 16 audio programs,
while MPEG4 supports an essentially
unlimited number.
So we think there is no technical
reason why your suggestion couldn’t
be implemented, as long as the TVs
decoding the streams can handle more
than one or two audio programs (and
surely they should).
You would have to convince the
broadcasters to add those channels,
however. Even people with reasonably good hearing can have trouble
understanding dialog in TV programs
with loud background music or sound
effects. Some programs seem to have
especially muted-sounding dialog.
You are right that 5.1/7.1 encoded
transmission usually have the centre channel carrying speech and little
else. This is a good reason to have a
surround sound system with a centre
channel (even if you don’t need the
rear channels), as it can make dialog
significantly more intelligible. Not
all broadcasts have surround sound
encoding, though.
Ultrasonic Anti-Fouling
fault LED flashing
I have built your Ultrasonic
Anti-Fouling MkII (May & June 2017;
siliconchip.com.au/Series/312) from
a Jaycar kit. During the testing step,
without the transformers installed, I
adjusted and measured the following
voltages:
Input: 14.3V
Between pins 5 & 14 of IC1
socket: 4.95V
TP1: 1.155V
TP2: 0.5V
2200μF capacitor: 0V
When power is applied, the green
LED comes on for about three seconds, then goes off, and the fault LED
flashes. I tested all the resistors with a
multimeter before fitting and have now
removed and replaced them with new
resistors, a new 20MHz crystal and
even a couple of the capacitors. No
Australia’s electronics magazine
change, still the fault light is flashing.
I’ve covered each high-voltage part
and under the crystal with conformal
coating to make sure it does not short
on the board.
I tried adding a 470W 1W resistor
between the drain and source of the Q5
Mosfet, as you’ve suggested in the past
to fix similar faults, but that didn’t help
either. I also replaced the 2200μF 25V
capacitors that came with the kit with
Rubycon 25ZLH2200MEFC16X20
capacitors but still get the same fault
light. Does it matter that it does not
say “low ESR” on the packet? (T. S.,
United Kingdom)
• Those Rubycon caps are suitable;
they are listed as low-impedance. As
it seems the capacitors are not leaky,
we think that Mosfet Q5 isn’t charging
the capacitors. Check this Mosfet and
whether it is being driven at its gate
when power is switched on.
There should be a square wave at
pin 6 of IC1, and the gate voltage of
Q5 should start to increase above
the source. Over a few seconds, this
voltage should go above 3V, and the
2200μF capacitor should begin to
charge. Read the section entitled “Soft
start facility” in the instructions, and
check if this is happening with your
Anti-Fouling unit.
Running SC200 from a
35-0-35V transformer
I have a quick question concerning
the SC200 Power Amplifier modules
(January-March 2017; siliconchip.
com.au/Series/308). I’ve read in your
articles that for the lower power version, using a 160VA transformer with
30-0-30V secondaries, you suggest
changing the 22kW resistor between
the collector of Q7 and ground to 15kW,
and the two 6.8kW resistors at the collector of Q6 to 4.7kW.
As I’m using the Ferguson transformers from my old ETI500 with
35-0-35V secondaries, should I change
those resistors to 18kW and 5.6kW,
respectively? (T. B., Bumberrah, Vic)
• The values you have suggested are
about right.
MMBasic and
PRINT USING
I have looked in all the MMBasic
Manuals (versions 4.5 to 5.05.03) and
on Geoff Graham’s Maximite website,
but I cannot find any reference to the
siliconchip.com.au
PRINT USING command. Is there a
workaround? I have several BASIC
programs I want to convert to MMBasic from the Amiga, Amstrad, Commodore 128 and TRS-80.
Also, could you let me know how
many articles are in the series “Getting
Started with the Maximite”, which I
believe started in February 2017? (R.
M., Melville, WA)
• Geoff Graham responds: As you
have discovered, PRINT USING is not
implemented in MMBasic. Use the
Str$() function instead, which provides a lot of the same functionality
(although the syntax is different).
The “Getting Started with the
Micromite” articles were published
in the February, March, May & June
2017 issues. See siliconchip.com.au/
Series/311
Sourcing parts for
Ultra-LD Mk.4 Amp
I would very much like to build the
Ultra-LD Mk.4 200W amplifier, power
supply and Mk.3 speaker protector
(July-October 2015; siliconchip.com.
au/Series/289).
I’m starting to investigate the
availability of parts before deciding
whether to proceed. Are there any
parts in those designs that will likely
be hard to find?
Also, this would be my first Silicon Chip build, and I don’t have any
preferred suppliers. I see your references to suppliers such as element14,
Rockby, Altronics, Mouser, Digi-Key
and Jaycar. I also see that Altronics
have a kit for the power supply, and I
can obtain the circuit boards plus the
SMD parts for the Speaker Protector
Mk.3 from Silicon Chip.
Does anyone supply more complete
kits for the amplifier at all? As you can
understand, shipping costs will be significant if I need to source lots of partial shipments (to New Zealand) from
different suppliers.
Sourcing the correct transformer is
a problem. I haven’t found any suppliers that list a version with 2x40V
plus 2x15V secondaries. The power
supply kit available from Altronics
doesn’t appear to include the transformer. I have had discussions with
a transformer manufacturer here in
Christchurch, but I’d need more detail
on its specifications before proceeding.
If I need to have a transformer
built, can I assume the following? The
siliconchip.com.au
40-0-40 secondary will need to handle
up to 300VA continuously. It should
preferably have a silicone steel core,
and the lowest practical winding resistance using copper, not aluminium. (J.
G., Christchurch, NZ)
• As far as we know, all the parts to
build those modules are still available. There are a few parts that you
will probably have to order from us.
That includes the PCBs plus the frontend transistors for the Ultra-LD Mk.4
amplifier modules, we sell these at:
siliconchip.com.au/Shop/7/3400
The PCBs and other parts can
be found at: siliconchip.com.au/
Shop/?article=8959
As for the less commonly available
parts, it depends on which supplier(s) suit you best. We suggest you try
Mouser or Digi-Key first, as they are
likely to have the largest proportion
of the components you need, and you
will be ordering enough to get free
delivery.
They send out orders pretty fast;
usually, we receive parts from those
two suppliers within a week of ordering. For the remainder of the components, especially for ‘generic’ things
like capacitors and through-hole resistors, try your local Jaycar store.
Altronics have a good selection too,
and if you will be ordering the power
supply kit from them, you can get
many of the other parts delivered at
the same time.
As for the transformer, you are correct that the Altronics part we used
has been discontinued and it’s difficult to find a replacement. You could
have a transformer made, but also
consider using two separate toroidal
transformers, one around 300VA with
two 40V secondaries and one smaller
2x15V (say 30VA). Both are available
off-the-shelf.
The only real disadvantage of this
configuration is the extra space and a
bit more wiring. There are some advantages - you might get a bit more power
for the main amplifier modules since
you won’t have the preamp draw on
that transformer.
Your suggestions for the transformer
specifications seem sound, although
you didn’t mention it being toroidal,
which we strongly recommend as they
have lower external magnetic fields. If
you do have to get one made, see if you
can get it with an outer electrostatic
shield layer. That helps to reduce the
hum field.
Australia’s electronics magazine
Faulty batch of
transistors
I purchased several Ultra-LD
Mk.4 Amplifier PCBs from your
Online Shop, along with the required
HN3A51F and HN3C51F transistors.
This project was published in the
July-October 2015 issues (siliconchip.
com.au/Series/289).
Following the 12-step setup procedure in the third article, steps 1 to
11 were successful, but I could not
achieve the desired offset voltage (step
12) on any of the six amplifiers I assembled. The voltage across the amplifier
outputs is far too high. My understanding is that it should be almost
0V. VR2 has practically no effect on
the DC level.
The voltages across the 68W emitter
resistors of Q2a & Q2b measure 60mV
rather than the 135mV specified; the
voltage across the 12kW resistor in
series with LED1 is 20V, not 24V; and
the voltage across the 330W resistor
at the emitter of Q3a is 580mV rather
than 600mV.
When I feed a signal generator into
the amplifier, the amplifier goes into
distortion for all frequencies above
1kHz. Interestingly, all six modules
are performing (faulting) precisely
the same.
I think the fault is with the HN3C51F
transistors (Q2). I am confident that the
output stage is stable and is operating
correctly. (I. P. V., Karrinyup, WA)
• We tested several of the HN3C51F
transistors that we have in stock, and
it seems that we have received a batch
of duds.
It isn’t that they are out-of-spec transistors; they do not behave like transistors at all, and different samples we
tested all behave differently. So it must
be a manufacturing failure.
Luckily, we were able to find and
source a reasonable number of the
only compatible substitute part, also
now discontinued, the IMX8-7-F. We
have tested several of the devices that
we received, and they seem to be fine.
So from now on, we will supply IMX8-7-F transistors instead
of HN3C51F (siliconchip.com.au/
Shop/7/3400) and we will send you
replacements for the faulty transistors
you received.
Luckily, Q2 acts as the current mirror for the input pair, so the performance of these transistors is nowhere
near as critical as the HN3A51Fs. We
August 2021 109
still have a reasonable number of those
in stock.
By the way, it looks like the original circuit diagram (Fig.1 on p34-35 of
the August 2015 issue) had an error.
The 135mV specified for the 68W emitter resistors of Q2a & Q2b should be
closer to 68mV as the 2mA from Q3a
is split between these two resistors in
the quiescent condition.
Hence, your voltage measurements
were all close enough to be considered correct.
Operating hydronic
heating during blackout
Last Wednesday, a storm broke hundreds of trees near our home, and this
is the sixth day without power.
We have hydronic heating and plenty
of gas, but we can’t run it because the
installer says that Bosch boilers are not
compatible with generators. They gave
no technical explanation for why this
is the case, nor any solution.
A local electrician said to connect
Neutral to the generator ground, which
sounds dangerous to me. I have also
heard about difficulties powering stationary computers, washing machines
and some fridges from generators.
Is it possible to run the hydronic
heating controller from a generator?
(V. K., Mt Dandenong, Vic)
• It’s difficult to answer your question without knowing what sort of
generator you have. Generator outputs vary considerably depending on
whether they are electronically synthesised (inverter generator) or not,
and whether they have a pure sinewave output, modified sinewave,
square wave etc.
If you have an inverter generator
with a pure sinewave output, virtually
any equipment should be able to run
from it the same as it does from the
mains. Just make sure that the generator has sufficient peak and continuous current/power capability for the
load(s) attached. The pure sinewave
output would be cleaner than the typical mains waveforms!
The primary power consumption in
a hydronic heating system will be the
water pump. If the pump is modestly
sized, it will probably not draw more
than a few amps, so even a modest
pure sinewave inverter running from
a reasonably-sized lead-acid battery
should be able to run it.
We do not suggest running sensitive
110
Silicon Chip
loads like computers or computercontrolled equipment from a generator without a pure sinewave output.
Their waveform can be very distorted,
and the amplitude and frequency can
vary considerably. That is probably
what you are referring to when you
mention stationary computers, washing machines and fridges.
Easy way to calibrate
multimeters
I have seven multimeters. Many of
them are not used regularly, so I have
stored them without batteries in the
original boxes, and they remain in
good condition.
It would be expensive to get them
professionally recalibrated, so I am
building the Precision 10V DC Reference for Checking DMMs (March 2014;
siliconchip.com.au/Article/6729) and
have ordered 10W, 100W, 1kW, 10kW &
100kW ±0.1% resistors. I plan to put
all these in an enclosure.
I know this will not be the same as
getting them professional calibrated;
it is only to check that they are still
within their manufacturer’s specs so
that I can use them with confidence.
I have ordered the AD587JNZ and
the resistors from element14. Do you
have any comments on this? (R. M.,
Melville, WA)
• That sounds like a reasonable
approach. You will probably find that
many of your multimeters are still spot
on. They can drift over time, but don’t
always do so.
You could also use such a setup to
calibrate the lower current ranges, in
combination with a variable bench
supply, ideally with an adjustable
current limit. You would need to calibrate one meter’s voltage ranges first.
Connect the meter in series with
one of the lower-value precision resistors, with the calibrated meter across
the resistor. Adjust the supply voltage
until you get very close to 10mV across
the 10W resistor.
You then know that the current is
very close to 100mA. The resistor dissipation will be 100mW in this case,
so keep in mind the resistor’s power
rating.
Induction Motor Speed
Controller radiates EMI
I have built your Induction Motor
Speed Controller (April & May 2012;
Australia’s electronics magazine
siliconchip.com.au/Series/25) from an
Altronics kit (Cat K6032) for use on
my pool pump, as per the instructions
included with the kit. The pump starts
and runs as described, but the controller is emitting RFI that interferes with
our AM radio reception. The interference is quite evident and disturbing.
Our AM radio uses a loop antenna
mounted in the ceiling and gives excellent interference-free reception, unless
the controller is running. The controller is located in the pool shed, which
is about 10 metres from the house in
the corner of our yard, so I cannot
increase the physical separation. I am
also concerned that I will be causing a
nuisance to my neighbours.
The pump being controlled is an
860W Davey Silensor which, according to my power meter, is drawing
around 990W without the controller
and about 330W with it. So it should be
well within the controller’s capacity.
The controller and pump leads are
both around 1.8m long and cannot be
shortened significantly. The Altronics
kit came with a plastic case, as per your
article. The pool shed is metal and is
not Earthed in any way (I’m not sure
if that is required). The radio and pool
shed are on the same mains circuit.
Please give me suggestions on how
I can reduce this interference. (J. M.,
via email)
• We tested whether the IMSC interfered with AM radio reception during
the development phase. We did this
while it was connected to a pool pump
and operating. Bringing a portable AM
radio close to the IMSC only resulted
in a small amount of hash pickup at a
range of about 1m. With the radio more
than 2m away from the controller, very
little to no interference was apparent.
So your controller appears to be creating a great deal more EMI/RFI than
our prototype. We therefore suspect
that your problem is related to noise
coupled onto the mains wiring, rather
than direct radiation from the unit or
its wiring.
First, check your mains Earthing.
The effectiveness of the line filtering
is only as good as the Earthing. This
could be a problem if the controller is
at the end of a long cable run, and the
Earth impedance is on the high side,
or if your domestic Earth connection
is not good. You might need to have
an electrician install an Earth stake in
the pool shed.
continued on page 112
siliconchip.com.au
If the Earth is solid, then it would
be worthwhile trying a bigger mains
filter. This could be as simple as winding the mains wires through a toroidal
ferrite core.
Speaker Protector not
sensing AC
I have built the October 2011 Loudspeaker Protector module (siliconchip.
com.au/Article/1178) from an Altronics kit (Cat K5167).
I configured it for my supply rail
voltage and tested it with the prescribed method, and it seemed fine.
However, as soon as I connect the AC
sense lines from my transformer, it
refuses to work.
Connecting AC sense to the positive
rail as detailed in the instructions and
performing all other tests shows the
module to be working.
Can you enlighten me as to the likely
cause of this problem? (D. J., Mandurah, WA)
• The first thing to do is check that
you have wired up the transformer to
the AC sense terminals correctly. Typically, you would have a centre-tapped
winding with the centre tap Earthed
and the other connections going to
both your bridge rectifier AC terminals, and the terminals of CON2 on
the Speaker Protector.
Assuming the connections are correct, verify that the base voltage of Q2
is low (below 0.2V) when the AC voltage is present at the AC sense input. If
that is incorrect, then check diodes D2
and D3 and the transistor Q1 to ensure
they are orientated correctly, have
good solder joints and are not faulty.
That it worked with a DC test suggests transistor Q1 is working OK and
that at least one of diodes D2 & D3 is
functioning correctly.
It could be a problem with the resistor or capacitor values around Q1. If
the 470nF capacitor is not soldered
correctly or has the wrong value, the
circuit will work with DC voltage
applied but not AC. Similarly, if the
resistor values are wrong, the circuit
might not hold up through dips in the
AC voltage.
Flexitimer with higher
supply voltage
Many years ago, I built the PICBased Flexitimer Mk.4 (June 2008;
siliconchip.com.au/Article/1847) from
112
Silicon Chip
a Jaycar kit (Cat KC5464). Can it be
modified to run from a 24V supply?
(J. S., via email)
• You need to change the relay to a
compatible type with a 24V DC coil,
the 470μF capacitor to a 35V rated
type, and the 1kW LED current-limiting resistor to 2.2kW.
AEE ElectroneX.......................... 7
Incorrect component in
low ohms meter
Control Devices..................... OBC
Advertising Index
Altronics...............................83-86
Ampec Technologies................. 25
I have built the Low Ohms Tester by
John Clarke from the June 1996 issue
(siliconchip.com.au/Article/4987), but
I can’t get it working. The text says that
the voltage at pin 2 of IC1 should be
the same as pin 3.
Adjusting VR1, I can get 2.4V on
pin 3, so it appears REF1 is working
OK. But the voltage at pin 2 is 1.64V. I
have replaced IC1 and Q1 to no avail.
(N. L., Christchurch, NZ)
• Since you have replaced IC1 and
Q1, that seems to rule out either component being faulty (which would
explain what you are seeing).
However, if Q1 is the wrong type
or orientated incorrectly, that would
cause this sort of fault. The only other
possibilities are a lack of continuity or
incorrect value with the 2.4kW resistor, trimpot VR2 or the 200W resistor.
Try changing range switch S2 to see
if that has any effect; if it does, it is
likely one of the latter three components at fault. Note that if this part of
the circuit is operating normally, pin
6 of IC1 should be around one diode
drop (approximately 0.6V) below the
voltage at pins 2 & 3.
Dave Thompson...................... 111
Pulse generator circuit
wanted
Vintage Radio Repairs............ 111
I’m interested in building a pulse
generator. I found a pulse generator
design in Practical Electronics, February 1979. Can you suggest a circuit as
simple as that one, but up to date with
similar specifications and features? (R.
M., Melville, WA)
• We published a pulse generator
circuit in the Circuit Notebook section
of the November 1997 issue, which has
similar features to the one you refer
to (siliconchip.com.au/Article/5833).
However, there was no PCB design to
accompany that circuit.
You could also build up the Practical Electronics design as there is nothing wrong with it. All the parts used in
that circuit are still available.
SC
Australia’s electronics magazine
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Microchip Technology.................. 5
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Notes & Errata
Ultra-LD Mk.4 Amplifier, July-August
2015: the circuit diagram (Fig.1)
incorrectly specifies 135mV across
the 68W emitter resistors of Q2a
& Q2b, the correct value should be
around 68mV.
The September 2021 issue is due
on sale in newsagents by Thursday,
August 26th. Expect postal delivery
of subscription copies in Australia
between August 25th and September
10th.
siliconchip.com.au
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