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Advertising Index Altronics.................................41-44 Blackmagic Design....................... 9 Dave Thompson........................ 111 DigiKey Electronics....................... 3 Emona Instruments.................. IBC Hare & Forbes............................ 6-7 Icom Australia............................. 14 Jaycar.......................IFC, 11, 15, 29 ............................54-55, 85, 97, 103 Keith Rippon Kit Assembly....... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology....... OBC, 13 Mouser Electronics....................... 4 PMD Way................................... 111 Quest Semiconductors............... 10 Silicon Chip Back Issues........... 53 SC Ideal Bridge Rectifiers........... 84 SC Pico W BackPack.................. 87 SC Programming Adaptor........ 109 Silicon Chip Shop............ 106-107 Silicon Chip Songbird.............. 104 The Loudspeaker Kit.com.......... 12 Wagner Electronics................... 105 Notes and Errata Mains Power-Up Sequencer, February & March 2024: in the Fig.3 circuit diagram (February, p52), fuse F1 should be rated at 10A, not 1A. Also scope grabs 1 & 2 show the current drawn by three amplifiers in parallel, not one. Ideal Diode Bridge Rectifiers, December 2023: 1.5mm diameter wire is too large for the SOT-23 version PCB pads; use 0.7-1.0mm diameter wire or lead off-cuts. GPS-Disciplined Oscillator, May 2023: some PCBs we sold had manufacturing errors with the four pins of REF5 (plus one nearby) shorted to the ground plane. If you have one, you can either drill those holes out slightly larger to break the connection to the plane and solder the wire link on the top, or contact us for a replacement board. Next Issue: the April 2024 issue is due on sale in newsagents by Thursday, March 28th. Expect postal delivery of subscription copies in Australia between March 27th and April 12th. 112 Silicon Chip bridge all the pins on each side, then alternately heating them while gently pulling up on the chip with tweezers. Either way, you will need to use flux paste and solder wick (pressed down firmly) to clean off all the remaining solder before placing a new chip. socket that is affecting operation. Also check the continuity for the tracks that you cleaned. While you’re at it, verify that the silicone insulating washers for Q1, Q2, D1 and D2 are insulating the device tabs from the rear panel/heatsink. Fixing Multi-purpose Fast Battery Charger FM antenna recommendations I built a Dick Smith K-3216 battery charger kit many years ago and have not used it in a while. I needed to recharge a 6V car battery with the charger this month, but it had stopped working. I found that the output fuse had blown, so I replaced it with another, which fused at switch-on. I took the cover off the unit to find that some sort of mould or corrosion had spread over one corner of the circuit board. The residue was on both sides of the circuit board, over the main switching inductor and between the rear panel and the instrument case. It appeared to follow the circuit tracks and parts soldered to the board; however, there was none around the electrolytic capacitors. They looked like new. It was hard-attached to the circuit board and components; I had to scrape it off with a flat-bladed screwdriver and wire brush. I then used WD40 to remove it from large components soldered to the board. The case was cleaned with steel wool and washed. When dry, I put it back together and followed the testing procedure in the article. All tests passed bar one: the measured output voltage should be around 10V on the 6V battery selection. My reading was 23V, no matter what settings were selected. What should I do to get the 10V on the output terminals? (K. W., Manly, Qld) ● That kit appears to be for the Multi-purpose Fast Battery Charger from the February and March 1998 issues (siliconchip.au/Series/144). The incorrect output voltage is likely due to a problem with transistor Q1; it seems it is continuously switched on. That could be due to a fault in it or transistor Q3. Check that Q1 and Q3 read open-­ circuit between the collector and emitter when the power is off. If you find a short circuit between the collector and emitter of either or both transistors, you will need to replace them. There could also be residue in IC1’s I wish to build or erect an FM antenna for the tuner in my hifi receiver. I noticed that Silicon Chip had an article in the March 1998 issue, but as it turned out, I have every issue from April 1998 (plus August 1997), so I just missed out. Is there a later article or an alternative to this antenna? Being a Yagi design and therefore directional, where can I source the information regarding the location of the FM broadcast transmission sites? I assume they’ll all be in approximately the same location here in Newcastle. Also, the transmission polarity appears horizontal, but car antennas are vertical. Do they transmit in both polarities? Any help would be greatly appreciated. (T. C., Newcastle, NSW) ● Yagi antennas are the best for FM radio. Cars mainly use vertical antennas because that is the only practical solution. Typically, FM transmission antennas provide both vertical and horizontal polarisation. That makes the transmission suitable for mobile use (eg, in cars) and for fixed antennas (with a horizontal orientation). If the transmission is purely horizontal or vertical, a receiving antenna will have more signal pickup when placed in the same plane as the transmission. However, there will still be reception if the receiving antenna is mainly in the orthogonal plane. We published a more recent FM antenna design in the October 2015 issue (siliconchip.au/Article/9137). Transmission antenna locations can be found at siliconchip.au/link/abse If you need one, you could get a copy of the March 1998 issue. While we have sold out of printed back issues of that month, you can can get access to view or download a PDF copy from siliconchip.au/Shop/12/3277 or order a photocopy of an article in that issue from siliconchip.au/Shop/2/265 It can also be obtained as part of our PDFs on USB (siliconchip.au/Shop/ digital_pdfs). SC Australia's electronics magazine siliconchip.com.au