From: firstname.lastname@example.org (N. Thornton)
Subject: Re: maximum reverse voltage allowed on electrolytic caps?
Date: 14 Nov 2002 17:28:29 -0800
References: <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 15 Nov 2002 01:28:30 GMT
"Bill Sloman" wrote in message news:...
> "Spehro Pefhany" wrote in message
> > Baz@NOSPAMporteraudio.co.uk (Barry E Porter) wrote:
> > >Depends upon how long it's there. Some makes of electrolytic (e.g
> > >Philips) don't even like no bias voltage for any length of time, and
> > >turn into short circuits after about 6 months of continuous use
> > How does the capacitor know that the item is being used
> > continuously rather than just sitting on the shelf, if the bias
> > voltage is zero?
> It doesn't. If you take old capacitors out of store, it is always a good
> idea to "re-form" them by hooking them up to a DC source close to their
> rated voltage, via a resistor that will drop their rated leakage current at
> that voltage.
> One of the legends at Geoge Kent in the 1970's was about a steel mill that
> had a couple of racks of George Kent analogue process controllers, which had
> been ordered and installed several years before they were needed. When they
> were finally powered up, most of the reservoir capacitors blew up. The
> customer was not impressed, and even less impressed to learn that the
> controllers were out of guarantee.
> Bill Sloman, Nijmegen
Its funny, I hear these kind of stories. But I still have some NOS
eletrolytics left from 1969, and very occasionally I use a few for 1
off tests, and I've yet to have any problems with them. They're
Sprague, Philips, I think another make too. One day they'll get slung
in a clear out, but for whatever reasons they're still there, and
still work. I cant remember why theyre there to be honest, but I know
they have been useful at some point.
I tried reforming 1930s caps when I did my big radio, but with not