Notes & Errata
Busy Loo Indicator, January 2021: at the bottom of the left-hand column on p79,
where the text says the inputs of IC1b are normally high, it should read IC1d instead.
Mini Digital AC Panel Meters, January 2021: if the current transformer secondary
is not terminated with a low impedance, it will generate a very high (and potentially
dangerous) voltage if any significant AC current is flowing in the primary. So make
sure to connect the secondary leads of the CT to the panel meter before any current
is allowed to flow through the primary.
Radiating test antenna for AM Radios, Circuit Notebook, January 2021: the
ferrite rod is 200mm long, not 400mm as stated in the text.
Vintage Battery Radio Li-ion Power Supply, December 2020: on page 28, the
text refers to a 220µF capacitor being charged via a 220W resistor. The capacitor
value is actually 10µF.
Colour Maximite 2, July & August 2020: the SD card socket specified for this
project (Hirose DM1AA-SF-PEJ(21)) is being discontinued by the manufacturer.
Instead, use the DM1AA-SF-PEJ(82) which costs the same and fits the existing
footprint on the PCB.
The March 2021 issue is due on sale in newsagents by Thursday, February
25th. Expect postal delivery of subscription copies in Australia between
February 23rd and March 12th.
Advertising Index
Altronics...............................21-24
Ampec Technologies................. 37
Dave Thompson...................... 111
Digi-Key Electronics.................... 3
Emona Instruments................. IBC
Jaycar............................ IFC,53-60
Keith Rippon Kit Assembly...... 111
LD Electronics......................... 111
LEDsales................................. 111
Microchip Technology............ OBC
Ocean Controls........................... 5
Silicon Chip Binders............... 111
pair of Ultra-LD Mk.3 amplifier modules (March-May 2012; siliconchip.
com.au/Series/27). The transistors
specified for Q1 and Q2, 2SA970 lownoise PNP bipolar transistors (BJTs),
seem to be no longer available.
I am considering using KSA992s
as a substitute. Do you think this will
compromise the performance of the
amplifiers? (I. S., Mitcham, Vic)
• The KSA992 looks OK. It’s hard to
be sure because the way they specify
the noise voltage in the data sheet is
not very useful. We don’t think you
will notice the difference (if any).
We can see some online sellers offering 2SA970s, but we think many
of them are counterfeit parts. Some
people have said that the clone parts
work well, while others say they are
not low-noise types; it probably depends on the luck of the draw. Your
suggestion of using KSA992s is safer
since you can get them from a reputable supplier.
Old remote preamp
not recommended
I was browsing old issues of Silicon Chip and found a project by John
Clarke called the Stereo Preamplifier
with IR Remote Control (September &
November 1993; siliconchip.com.au/
Series/168).
Since then, many newer designs
have been published like the Ultra-LD
Stereo Preamplifier & Input Selector
112
Silicon Chip
that I am happily using together with
the Ultra-LD Mk4 amp. What caught
my attention was the absence of a volume pot and the LED display.
I was wondering if that design is still
valid and if I could build it? I’d need
to find a few replacement components
that’d be obsolete by now. I checked
that I could source the microcontroller online; however, I have no way to
program it. Do you have any advice on
this? (O. A., Singapore)
• That Preamplifier would be extremely difficult to build at this late
date, as many critical parts would be
very difficult to obtain.
The microcontroller would be difficult to program as we don’t have the
facilities for that processor anymore.
We do not recommend that you start
building this project.
Note that we are working on a new
digital preamp design with remote volume, bass and treble controls; however, it is not yet finished, and we don’t
know when it might be published at
this stage.
Problem with 3-channel
Rolling Code Remote
I built this project, described in
your August & September 2009 issues
(siliconchip.com.au/Series/39) from a
Jaycar kit, Cat KC5483. All functions
are operational, but the range is only
about 3m.
I have checked the antennas on both
Australia’s electronics magazine
SC Micromite BackPack............ 96
Silicon Chip PDFs on USB....... 87
Silicon Chip Shop.................... 97
The Loudspeaker Kit.com........... 7
Tronixlabs................................ 111
Vintage Radio Repairs............ 111
Wagner Electronics................... 51
the transmitter and receiver but cannot
find a fault in the construction. Do you
have any suggestions? (G. P., via email)
• The most likely cause is the soldering to the coiled wire antenna. The
wire is enamel-coated, and unless
this is scraped off well before soldering, it may not form a good connection, reducing the effectiveness of the
antenna.
You probably have already checked
these connections. However, a multimeter measurement of resistance from
the antenna input on the receiver module (or output for the transmitter module) to the free end of the antenna will
verify if this is a low-ohms connection, as expected, or high-resistance/
open-circuit.
Another thing to check is that there
is the full 5V DC supply to the transmitter and receiver modules and that
the transmitter supply stays at 5V
when transmitting.
SC
siliconchip.com.au
