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is GND. I have confirmed continuity between the two pads. Has there been a circuit diagram change? I wonder if someone there would be able to comment on what looks like an error. (M. F., Gulfview Heights, SA) ● It isn’t marked as such on the PCB, but pin 1 is at the other end of CON4. The clue is that pin 1 has a square pad, while the others are rounded. So that pin of CON4 you are referring to is actually pin 13 (second from the end), which connects to JP2 as expected. The trace to pin 9 is on the underside of the PCB. This probably isn’t helped by the fact that pins 15-18 don’t exist on Advertising Index Altronics.................................43-50 Blackmagic Design....................... 7 Dave Thompson........................ 111 DigiKey Electronics..................OBC Electronex..................................... 5 Emona Instruments.................. IBC Hare & Forbes............................. 11 Jaycar............................. IFC, 12-15 Keith Rippon Kit Assembly....... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology.................. 9 Mouser Electronics....................... 3 PCBWay....................................... 39 PMD Way................................... 111 Rohde & Schwarz........................ 59 SC ESR Test Tweezers............... 92 Silicon Chip Back Issues........... 78 Silicon Chip Binders................ 111 Silicon Chip PDFs on USB......... 61 Silicon Chip Subscriptions........ 89 Silicon Chip Shop.............. 97, 108 The Loudspeaker Kit.com............ 8 Wagner Electronics................... 101 Next issue of Silicon Chip Next Issue: the June 2026 issue is due on sale in newsagents by Monday, May 25th. Expect postal delivery of subscription copies in Australia between May 22nd and June 9th. 112 Silicon Chip CON4 (on the PCB); they correspond to the four pins at the other end of the LCD module for its (unused) SD card slot. Bench supply upgrade query Can you advise me if Silicon Chip has published a design for a variable-­ voltage, variable-current linear power supply, delivering (say) 0-30V at 0-5A (or so), using something like 2N3055 series pass output transistors? I have recently acquired a WONI bench power supply that appears to be working, but the design is rather woeful, mainly in regard to the voltage control potentiometer. The design of the supply has the pot wired as an adjustable resistor (just two wires from the pot to the PCB) and the voltage variation is far from linear. Rather than playing around with the existing design, I think I would be happier to build and retrofit a Silicon Chip design, which I know would perform properly. (P. W., Pukekohe, New Zealand) ● We have a few designs that may suit you. In October 2019, we published a 45V, 8A linear bench supply (siliconchip.au/Article/12014). It would have plenty of headroom to operate at 5A but, being a linear supply, it is on the bulky side. Alternatively, you could consider the 40V Switchmode/Linear Bench Power Supply (April-June 2014 issues; siliconchip.au/Series/241). It uses a fast-acting final linear stage for output regulation and current limiting, with a tracking switch-mode regulator before it for better efficiency. As such, it doesn’t require a large heatsink. Using a Pico 2 W for the WiFi Time Source I have several clocks I wish to adapt to using the New GPS-Synchronised Analog Clock from September 2022 (siliconchip.au/Article/15466). I was intending to use the WiFi Time Source for GPS Clocks project with it (June 2023; siliconchip.au/Article/15823). Is there any advantage to using a Pico 2 W over the Pico W in this project? If I use the Pico 2 W, what changes would I have to make to the WiFi Time Source project, if any? (P. N., Engadine, NSW) Australia's electronics magazine ● The Pico 2 W uses a different processor from the Pico W (RP2350A rather than RP2040) so you can’t load a UF2 file compiled for the Pico W on a Pico 2 W. It will just ignore it. In theory, the existing source code should compile if the target is changed to the Pico 2 W, but we have not tried that, or tested the result. So we recommend you stick with the Pico W since we know it works and have a compiled UF2 file ready to use. Also, there’s no real advantage to using a Pico 2 W in this scenario, and it costs more. While it’s possible that simply recompiling the code for the Pico 2 W target will be sufficient, there may be breaking changes in the C SDK and its API that mean that more work is needed. The Pico W’s capabilities are more than sufficient for the task, so we don’t see any need to port the code at this stage. The Raspberry Pi Foundation says that the Pico W will remain in production until at least January 2036. Case advice for Roadie’s Test Oscillator Can I use a plastic enclosure for the Roadie’s Test Oscillator project (June 2020; siliconchip.au/Article/14466)? I don’t need it to be drop-proof or rugged. (R. M., Melville, WA) ● Yes, a plastic enclosure is suitable. Note that you must use a type where the lid is attached to the base using screws to comply with safety standards restricting access to the coin cell that powers the oscillator. The cell can be a severe health hazard to young children if they can access it. RF Probe wanted I was just looking at a video from Carlson’s Lab where Carlson troubleshoots electronic circuits with a device he created himself that he calls the Carlson Ultra Probe. It is a very high-gain and sensitive amplifier that uses a coaxial cable as a probe. It can be used as an RF or AF detector and amplifier. I was wondering whether Silicon Chip has created such a project. (P. J., Lenah Valley, Tas) ● We published a similar Audio Signal Injector and Tracer with a matching AM Demodulator Probe in the June 2015 issue (siliconchip.au/ SC Article/8603). siliconchip.com.au