Having experienced several failed capacitors recently I decided it was time to have some means of checking them. A good way to find faulty electrolytics is to measure the equivalent series resistance (ESR) using an ESR meter.
There are some nice but expensive commercial products around and I am sure they work well. There is also a good design for a homebrew meter by G0NQE. This is my version built in a day from mainly from recovered components including an old plastic box. It works well.
Full details on the G0NQE site.
For more information about ESR see:
en.wikipedia.org/wiki/Equivalent_series_resistance
my.execpc.com/~endlr/esr.htm – includes a table of typical readings.
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