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Old Electrolytic - George A - 09-16-2020

Hi all - I have many, probably hundreds of "NOS" electrolytic caps left over from Polytone's inventory, probably dating from the mid to late 1980's. (They made an interesting tube amp called the Fusion to compete with Mesa Boogie - didn't really pan out for them).

They're nice looking caps - Mepco/Electa 310uf/300V - a couple in series would make a nice reservoir/smoothing leg.

My question - Is there any hope for using these, or am I asking for disaster if I do?  I've read about "reforming" capacitors - does anyone have thoughts or experiences related to this?

Thank you,

George


RE: Old Electrolytic - K O'Connor - 09-17-2020

Hi George A

Manufacturers of electrolytic capacitors state that the service life for any such cap is 14 years maximum, regardless of how the life expectancy calculation might go. Long before that time, DA and DF go crazy and the best range of performance is already lot even though for most applications the cap seems to function as usual. This is with voltage regularly applied. The shelf life of most caps is often only a year or less.

Whether reforming a cap starts the clock at zero again isa question - I would not think it is a complete zero but someone who knows more about the chemistry of the cap could say for certain.

Some builders and hobbyists like how series-connected electros sound; I personally prefer single units to withstand the voltage present.

Remember: The cap can be used to its full voltage rating - it stays healthier longer that way. Derating voltage simply allows the cap to deform to the actual voltage present.


RE: Old Electrolytic - makinrose - 09-23-2020

I wouldn't recommend it. Why? Three reasons:

A. Modern Radial Electrolytic are inexpensive, so I'm not sure how much you'd save by doing this once you took the time to reform the caps and perhaps later had to go back and troubleshoot caps.

B. Modern Electrolytic caps have better electrical characteristics.

D. Unless you are very sure that the reforming process has truly set your cap back "to zero" to I'd trade paying for few caps over having to re-cap an amp earlier than usual. Or if you build it for someone else having to deal with a reliability issue.

That's just an opinion!