[ARC5] Capacitors in command sets

Wed, 5 Feb 2003 18:02:16 -0800

All this talk of capacitor failures in command sets, reminds me of my BC-456 with
very low transmit audio.  Turned out to be the bypass cap on the mic input, C-54B
had failed open, or completely dried out, not leaky, just not a capacitor anymore.

Jack

Jack Antonio WA7DIA
[email protected]

----- Original Message -----
From: "Beckley, Stew" <[email protected]>
To: <[email protected]>; <[email protected]>; "ARC-5" <[email protected]>
Sent: Wednesday, February 05, 2003 8:07 AM
Subject: RE: [ARC5] Starting work on BC-453B

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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