Evaluate High uF Capacitors

[Longbow]

Here's a question for those interested in older linear mode power supplies. For many years computer grade power supplies used gigantic electrolytics to stabilize the power rails to logic boards (usually with TTL and ECL chips). Nobody designs circuits with these parts anymore, but let's say we want to evaluate an older 50,000 uF filter cap. These caps were designed to filter 120 cycle pulses riding on a dc level of 5-50 volts depending on the circuit. Other than an open or shorted part, what kind of testing would be used on monster sized filter caps?

[berniedd]

Re: Evaluate High uF Capacitors

Capacitance value, I would think. But how to go about it, I'm not sure. I don't know of any commercial equipment that measures that high.

[Jack Crow]

Re: Evaluate High uF Capacitors

Long Bow,
I suppose we could go back to basics.

Do a charge / discharge cycle into a known load resistor.

That will tell you if the value of the cap is close to spec.

Very often the best way is to sub in a good part for the suspect part and see what happens.

Jack Crow.