On Feb 18, 1:59*pm, "Henry Kolesnik"
wrote:
What's a good place to get some good ones, *reasonable? *I've got
several AA5 radios with hum and need to fix them. *All my new old stock
capacitors are dry.
thanks
Hank wd5jfr

Hey OM.
I used to make a living selling Mallory capacitors. Mallory came out
with a book called the Bird's and Bee's of electrolytic capacitors.
Well the electrolyte in these capacitors does dry out, but not from
sitting around in room temps. The electrolyte dries up from discharge
and charge, each time of a charge or discharge cycle the electrolyte
breaks down, into gas, that's why they have to be vented, or they
would explode. The electrolyte also dries up if you heat them up. In
the old days they used a lot of electrolyte.

So why don't they have capacity? The electrolyte in old style
capacitors has lots of room in between the plates and seperators, and
with time the electrolyte settles via gravity, At this point the
plates are no longer fully covered with electrolyte so the capacity
goes down the crapper.

When removed from scrap equipment , it is best to slowly cycle them
(charge/discharge) a few times up to the stated working voltage .
If necessary test them in a real equivalent circuit and check ripple
with a scope . A bit of work ,but imho a rewarding activity.

Frank GM0CSZ / KN6WH

^Is right for the most part, the key really is to ramp the voltage.
from 0 to full rated WVDC, up slowly, real real real slow, like days
to a week, this will wick the electrolyte back up on the plates and
once again the capacitor will be usable. So a NOS capacitor off the
self at room temp can be brought back from the grave

73 OM
de n8zu