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Surplus caps how old is too old?
Surplus caps how old is too old?
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Old 6th June 2002, 04:25 PM   #1
woody is offline woody
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Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
Surplus caps how old is too old?
Default Surplus caps how old is too old?

In cleaning out my garrage I found a box of electrolitic caps I had
bought back in 1980. They seem to still be healthy but is there any way to predict how long an old cap like this will last if put to
use. When charged up to their rated voltage these 15,000uf 63v
Marcom caps didn't seem to have any leakage current to speak of
and held a charge for a few hours when disconnected. I have 20 of these I would like to find a new home for but don't want to sell
anything that is likely to fail real soon.

Thanks for past and future help,

Woody AKA bob12345678
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Old 6th June 2002, 05:51 PM   #2
tiroth is offline tiroth  United States
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You could test the ESR. I believe a major failure mechanism is aging causes a rise in ESR, which causes higher dissipation, faster aging, etc.
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Old 6th June 2002, 05:57 PM   #3
Peter Daniel is offline Peter Daniel  Canada
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I like surpluss caps too. Check my other thread dealing with that matter: http://www.diyaudio.com/forums/showt...&threadid=3276
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Old 17th June 2002, 12:58 PM   #4
yeti is offline yeti  Germany
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Location: Ewersbach
Default old caps

Usually they should still be ok,but possibly the dielctric must be reformed.
To do so ,you can connect a variable power supply to the caps in series with an ammeter, now increase the voltage to 1/3 of the maximum voltage of the caps.
At the beginnig there will be a certain amount of leakage current that decreases after a while, if the leakage current is below 1 mA you can slowly increase the voltage applied.
If you reached Vmax * 1.2 at a reasonable leakage current the caps should do for te next 10 years.

regards; Arne
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