. Various k7204 - ESR & Low Ohms Meter free download

File name k7204 - ESR & Low Ohms Meter.pdf

Assembly Manual ESR & Low Ohms Cat No. K 7204 Meter by Bob Parker ACN 000 908 716 K I T Reproduced in part by arrangement Please read Disclaimer carefully as we with Electronics Australia, from their can only guarantee parts and not the January 1996 edition. labour content you provide. If you repair switch-mode power supplies, TV receivers, computer monitors, vintage radios, or similar equipment, and/or if you need to measure very low values of resistance, this proj- ect can save you lots of time and aggravation - as it has for me. It measures an aspect of electrolytic capacitor performance which is very important, but normally very difficult to check: the equivalent series resistance, or `ESR'. ome wise person once said, "The can do is give a low reading if the elec- currents, the electrolyte will start to S reliability of any piece of electronic equipment is inversely proportional to tro is nearly open circuit. decompose and the dielectric may dete- riorate - and the ESR will increase far the number of electrolytic capacitors in About ESR... more rapidly. it", and I doubt that many service techni- To make things worse, as the ESR cians would disagree! So what exactly is an electrolytic's increases, so does the internal heating Especially now that switch-mode equivalent series resistance? caused by ripple current. This can lead to power supplies (SMPSs) have been Electrolytics depend on a water-based commonly used in domestic VCRs and electrolyte, soaked into a strip of porous TVs, etc for a decade or so, one of the material between the aluminium foil most likely components to fail is the plates, to complete the `outer' electrical humble electrolytic. The symptoms can connection to the aluminium oxide be as diverse as a VCR's playback pic- dielectric coating on the anode foil. ture swimming in tiny dots, up to SMPSs The electrolyte has electrical resist- mysteriously self-destructing. ance which, along with the (negligible) As a service technician myself (though resistance of the connecting leads and I'd prefer to be a full-time designer!), I aluminium foil plates, forms the capaci- was just about tearing my hair out tor's equivalent series resistance. bec