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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