Testing caps?

[hostarn]

Greetings!

If I have neither capacitance meter or ESR meter, how can I now if a capacitor is good or faulty. It has no visible defaults.

If the answer is that I have to buy one of the above testers, which should I get. I'm thinking ESR. And I have yet to see a capacitance meter that can meusure above 20000uf. It should also be said that in my househould the budget for this kind of thing is strictly limited.

Regards,

Erik

[luka]

why would you need to meter caps above even few uF?
if cap holds rated voltage, the is probably is good, no?

[Conrad Hoffman]

Actually, given nothing else, if the cap holds voltage it's probably quite healthy. Still, there's nothing like knowing for sure, so I show you how to build a simple cap bridge using next to nothing here- http://www.conradhoffman.com/chsw.htm
If you have a good junk box or improvise, you should be able to do it for just a few dollars.

[peranders]

Originally Posted by hostarn

Greetings!

If I have neither capacitance meter or ESR meter, how can I now if a capacitor is good or faulty. It has no visible defaults.

If the answer is that I have to buy one of the above testers, which should I get. I'm thinking ESR. And I have yet to see a capacitance meter that can meusure above 20000uf. It should also be said that in my househould the budget for this kind of thing is strictly limited.

Regards,

Erik

Is it new or old caps?

ESR is only important if you drive them hard like in a switched power supply and some other heavy duty operation.

[hostarn]

thank you everyone, @ Peranders, they're old. Well, used. And how would I know if they hold rated voltage?

[peranders]

If they are dry the will have increased leakage and in general bad function but one easy way to find out is to charge them via a resistor, 10k or so and turn up the voltage so you will get 1-5 mA leakage. Let the current flow for some time and see if it will get less. If it tends to increase you have reach the voltage rating. A 35 V cap starts to leak at 42-48 volts if it's OK. It's important that you have a resistor in series because otherwise the cap can explode if you have a powerful voltage source.

How old are they, brand, type, capacitance, voltage rating?

[Enzo]

And the simple answer - charge the cap up, remove the charging supply, then measure the stored voltage with a meter.

[switchmodepower]

Or charge the cap with a constant current. Measure the time it takes to reach a given voltage and calculate capacitance.

Or charge the cap to a given voltage and put a known distcharge resisitor- remove source and measure the time it takes to discharge, then calculate capacitance.

[hostarn]

Thank you airbody. This might all work for you. But I'm sort of a layman so I just bought an ESR meter. I also just put it to good use. I have had a NAD C350 awaiting repair for a long and desperate time. In a few minutes with my meter I meusured all the caps in the amp IN CIRCUIT. I discover FOUR of them was open. I changed them, and now I'm dancing away in my living room.

Ta'