Fw: information needed on long term storage of vintage radioequipment (Collins S Line)

[talen]

What basically happens is that the electrolyte changes over time in electrolytic
capacitors under "non use". The electrolyte develops a lower resistance which
can cause enough current to flow initially, heating the capacitor, POSSIBLY
causing internal shorts, causing more current, etc until the electrolytic fails.
The best way is to limit this current by attaching the capacitor to a Capacitor
Checker and step the voltage up each time the eye is fully open until you reach
the working voltage. You will never exceed about 5ma this way. Do this a couple
of times and you are done.

By the way, ANY kind of voltage "ramp up" is better than "instantaneous"
application of full voltage to an old electrolytic capacitor....older circuits that
have a rectifier tube have "fillament warmup delay" vs where the rectifier tube has
been replaced with a solid state rectifier in old tube gear. Also the voltages on the
electrolytic are a little higher when changing to solid state rectifiers.

I don't know how long a time schedule is defined anywhere, but based on what
I've seen on a good ol' Heath IT-28 Capacitor Checker where I've taken old
caps and slowly charged them by waiting until the eye opens before going to
the next step and adding a margin of error and stabilization time, I would do the
following with the variac:

Start 25% rated output, leave for 1 minutes
Go to 50%, leave for 5 minutes
Go to 75%, leave for 10 minutes
Go to 100% leave for 30 minutes
(you can probably cut the times in half with no problem)

The only potential damage to an input (power) transformer I can think of is if
you don't do the above and the capacitor happens to short and the fuse is
slow in opening. Not to mention the potential mess.

73s  Kees K5BCQ


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From: MarjoriePistone <MarjoriePistone at EMAIL.MSN.COM>
To: HEATH at LISTSERV.TEMPE.GOV
Subject: information needed on long term storage of vintage radioequipment (Collins S Line)
Date: Thursday, February 24, 2000 12:34 PM

I would like information on preventing damage to and rejuvenate capacitors
in long term storage unused.
Xmtr & Rcvrs ( or other components) that have TRANSFORMER INPUTS by plugging
them into a variac and periodically (slowly) increasing the voltage on them.
Can that possibly damage the input transformer or other components in the
system and Can anyone suggest a time/voltage schedule to follow if the above
procedure is OK? I would appreciate any information.

Thank You
Bob

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