[ARC5] Starting work on BC-453B

Wed, 5 Feb 2003 11:07:22 -0500

I'm glad to see this cap reformation subject come up again, since every =
time it does, there's something new to learn. (Thanks Jim, and good luck =
on your 453!)

I now understand that all those triple-05 cans out of my 454/455/696/459 =
etc. that I thought I was "restoring" were actually just getting cooked =
to remove moisture. Most of them responded favorably (leakage current =
dropped off); only a few were totally shot.

Now for the question I haven't seen answered: What IS the acceptable =
leakage current per cap in those old triple-05's? I suppose there are =
two values worth quoting: a)The "spec" value for that particular cap (if =
anyone has the parchment on this), and b) an empirically derived value =
for proper and safe operation in a command Tx or Rx.

Any takers?

Thanks & 73,
Bud, WA2AUI

-----Original Message-----
From: J. Forster [mailto:[email protected]]
Sent: Monday, February 03, 2003 5:42 PM
To: [email protected]; ARC-5
Subject: Re: [ARC5] Starting work on BC-453B

[email protected] wrote:

> John:
>
> Because we have some new people on the list, it might make sense to go =
over
> the procedure to reform the capacitors.  I've done it before with good
> results.
>
> Thanks,
>
> Dave Jackson

Re-forming is a process used to recondition capacitors after long =
periods of
storage.  It mainly applies to electrolytics, but has some application =
to
leakages in other types.

The process is simple. You just apply a much reduced voltage (perhaps 5 =
to 10 %
of the rated voltage) to the cap from a high impedance source and watch =
the
current. It will decay with time (this is not the RC time constant). =
When the
current has stabilized, up the voltage another 5 to 10% and watch the =
current
again. Keep doing this until the rated voltage s reached, or the =
capacitor
fails.

I have used this procedure with sets that have been stored since WW II =
and they
work just fine, WITH ALL ORIGINAL CAPS.

YMMV,

-John

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