Old Electrolytic Capacitors?

[davent]

Hello,

I've got some small value electrolytic capacitors here (1uF, 2.2uF, 3.3uF) that are at least 20 years old and never been used. Would these still be good, is there any way to test them to see if they're still OK or should I just scrape a few pennies together and replace them?

Thanks for the help!
dave

[Pedal love]

What voltages are these rated at?

[kurtlives]

I would think smaller caps (voltage rating) would last longer than the filter caps in our amps that we are supposed to replace very  5 - 10 years. There is less electrolytic liquid and it would seem it would be harder for it to dry.

[davent]

Hi guys,

These are all just little ones I want to use in pedals, 50v and 63v, (although if they're any good they could be pressed into service as cathode bypass caps on preamp tubes.)

dave

[frank_p]

You have to measure the ESR (serie resistance that builds in the electrolytic):
There are some charts pointed by RG:

http://www.diystompboxes.com/smfforum/index.php?topic=72006.msg581498#msg581498

Also:
http://www.diystompboxes.com/smfforum/index.php?topic=65451.0

Also, search for ESR on the net, you should find some more info.


Yours

[bassmasta17]

i dont know anything about this but their are amps out their older that 20 that still work. They should work. just don't do this from what i said!

[R.G.]

Electro caps decay from sitting on the shelf. They decay in use, too. If held with a voltage on them and cool, they decay slowest. If hot, they decay faster.

Old, but unused caps may be OK, but I personally would only use them for temporary tinkering, not where I'd have to go troubleshoot a failure in a few weeks/months. Test them before using them.

[davent]

Electro caps decay from sitting on the shelf. They decay in use, too. If held with a voltage on them and cool, they decay slowest. If hot, they decay faster.

Old, but unused caps may be OK, but I personally would only use them for temporary tinkering, not where I'd have to go troubleshoot a failure in a few weeks/months. Test them before using them.

Thanks R.G. that's what I needed to hear.  Would be pretty foolish to use an old cap to save a dime then have to spend considerable time and energy troubleshooting later.

You have to measure the ESR (serie resistance that builds in the electrolytic):
There are some charts pointed by RG:

http://www.diystompboxes.com/smfforum/index.php?topic=72006.msg581498#msg581498

Also:
http://www.diystompboxes.com/smfforum/index.php?topic=65451.0

Also, search for ESR on the net, you should find some more info.


Yours

Thanks Frank, found a post in one of links you posted where R.G. describes some methods to test caps without having to spring for some new toys

Take care
dave