From: Joseph Legris
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Subject: Re: maximum reverse voltage allowed on electrolytic caps?
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Date: Wed, 13 Nov 2002 17:51:15 -0500
NNTP-Posting-Date: Wed, 13 Nov 2002 17:51:14 EST
Organization: Bell Sympatico
Bill Sloman wrote:
> "Spehro Pefhany" wrote in message
> > On Wed, 13 Nov 2002 18:18:24 +0000 (UTC), the renowned
> > 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
But I doubt the ANY manufacturer makes an electrolytic capacitor that
must be reformed after only 6 months on the shelf.
Oh yeah... except possibly the ones they put on motherboards.