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MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz LEDsales KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com FOR SALE LEDs and accessories for the DIY enthusiast LEDS, BRAND NAME AND GENERIC LEDs, filament LEDs, LED drivers, heatsinks, power supplies, kits and modules, components, breadboards, hardware, magnets. Please visit www.ledsales.com.au PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. PCB PRODUCTION Lazer Security PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au WE OFFER KITS, LEDs, LED assemblies and all sorts of quality electronic components, through-hole and SMD, at very competitive prices. Check out the latest deals at www.lazer.com.au For Quality That Counts... ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (02) 9939 3295. Your 0.7-1.0V readings across the safety resistors is good, as is the fact that it increases slowly as you rotate VR1 clockwise. That, combined with the low output offset voltage, makes it very likely that the modules are working correctly. Those substitute transistors have specifications that are very close to the originals and should not cause any problems. The substitution was necessary as one of the originals is no longer made/available. Once the resistors are moved to the fuse locations, the voltage drop across them only depends on the output stage current, not the total module current. Since the initial bias is so low, the output stage is drawing almost no current, hence the low voltage drop readings at first. That probably should have been explained in the article. siliconchip.com.au Yes, there will be a slight variation in the current sharing. That’s part of the reason for the emitter resistors; they help to reduce the variation. Your measurements are fine, and we would not bother to make any further adjustments as long as the bias currents don’t keep increasing over time as the module warms up (thermal feedback). With the readings between 4mV and 6mV, you should get performance pretty much identical to the published graphs, and as long as the voltages are not creeping up, there is no risk of thermal runaway. Appliance Energy Meter voltage is wrong I built the Appliance Energy Meter (August-October 2016; siliconchip.au/ Series/302) and much of it works fine. Australia's electronics magazine The Micromite display comes on and I can set clock time. At first, I could calibrate the AC voltage readings to match the mains, but now I am unable to do that. I have checked voltages at various points as given on the circuit diagram and all check out except some around IC4 (the ACS718). I measure 4.87V at pin 10, 2.47V at pin 12 and 0V at pin 15. Pin 15 is shown as Vcc and should give 5V. I can measure 5V up to the 56kW resistor but not beyond. I can see the PCB track from pin 15 connecting to Earth at the end of the 2.2kW resistor. What am I missing here? Is the PCB faulty? If the 5V rail connected to Earth, I would think none of the other positive rail points would show a voltage. I have built many projects over many decades (back to Radio, TV continued on page 104 August 2024  103