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Practical Electronics Editorial offices Electron Publishing (Aust.) Tel +61 2 9939 3295 Unit 1, 234 Harbord Road Email pe<at>pemag.au Brookvale NSW 2100 Web www.electronpublishing.com Australia Address mail to: Electron Publishing (Australia) PO Box 194, Matraville NSW 2036 Australia Advertising enquiries +61 2 9939 3295 pe<at>pemag.au Editor Nicholas Vinen Publisher Nicholas Vinen Digital subscriptions Stewart Kearn Tel 01202 880299 Online Editor Alan Winstanley Web Systems Kris Thain Production Bao Smith Technical staff Tim Blythman, John Clarke Print subscriptions Practical Electronics Subscriptions PO Box 6337 Bournemouth BH1 9EH Tel 01202 087631 United Kingdom Email pesubs<at>selectps.com Technical enquiries We regret that technical enquiries cannot be answered over the telephone. We are unable to offer any advice on the use, purchase, repair or modification of commercial equipment or the incorporation or modification of designs published in the magazine. Questions about articles or projects should be sent to the editor by email: pe<at>pemag.au Projects and circuits All reasonable precautions are taken to ensure that the advice and data given to readers is reliable. We cannot, however, guarantee it and we cannot accept legal responsibility for it. Some projects and circuits published in Practical Electronics employ voltages that can be lethal. Do not build, test, modify or fix any mains-powered equipment unless you fully understand the safety aspects involved and you use an RCD (GFCI) adaptor. Component supplies Silicon Chip Publications may offer kits or other parts for making our projects, but not in all cases. When kits are not available, readers will need to find and source parts themselves. We advise readers to check that all parts are still available before commencing any project in a back-dated issue. 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The laws vary from country to country; readers should check local laws. 2 Volume 54. No. 4 April 2025 ISSN 2632 573X Editorial Equivalent Series Resistance testers are very useful One of our projects this month is the very useful ESR Test Tweezers tool, a handheld device that can measure capacitance (over a limited range) but, more importantly, can also accurately measure capacitor equivalent series resistance (ESR) down to tiny fractions of an ohm. I was a bit surprised when I looked back over the recent history of Practical Electronics and couldn’t find much in the way of ESR testers until our recent LC/ESR Meter from the August 2024 issue. Given how useful these devices are for repairing and servicing equipment, I expected other designs to have been published. For example, Silicon Chip magazine published Bob Parker’s ESR Meter Mk2 design in its March & April 2004 issues. It turned out to be an extremely popular project that was made into a kit by both Dick Smith Electronics and Altronics. The beauty of an ESR meter is that it can identify faulty electrolytic capacitors that otherwise seem fine. Electrolytic capacitors are probably the single most common source of faults in equipment these days as they have a much shorter lifespan than any other component, usually measured in thousands of hours. An electrolytic capacitor might look fine, and a capacitance meter may even give the expected reading. However, if it has developed a high ESR (often as a result of the electrolyte drying up or leaking out), it won’t properly perform its job of filtering or smoothing out voltages. An ESR meter will immediately detect this and pinpoint the capacitor(s) that need replacing. It is not uncommon to find a large electrolytic capacitor that seems fine on visual inspection and would normally have an ESR figure of 0.01Ω or less, that then measures several ohms! Such a capacitor is essentially no good for anything other than decoration at that point. Of course, if a capacitor has a bulging top or a brown stain around its base, you probably don’t need any test equipment to tell you it needs replacing. Unfortunately, faults aren’t always that obvious. That’s why an ESR meter is a worthy addition to a repairer’s toolkit. Errata Unfortunately, some errors in the Audio Out column last month were not spotted before it went to press: • In Fig.15 on page 24, the 1.5nF capacitor should be 1.5µF and the 47nF capacitor should be 4.7µF. • In Fig.22 on page 25, the 2.2nF capacitor should be 2.2µF. Nicholas Vinen, Electron Publishing (Australia)* Publisher & Editor, Practical Electronics Magazine * a division of Silicon Chip Publications Pty Ltd. Practical Electronics | April | 2025