Re: A funny thing happened on the way.....

To: tesla-at-pupman-dot-com
Subject: Re: A funny thing happened on the way.....
From: "Adam" <adamsmith-at-mediaone-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 19 Mar 2000 19:21:09 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

> Original Poster: "Jon Lagler" <rockcrawl-at-netzero-dot-net>
> 
> ...Upon closer inspection, I noticed one of the MMC caps had leaked
> oil. I peeled off the plastic wrapper, and the ceramic case was cracked. the
> funny thing is, it still measures OK with a DMM.

That's not at all unusual. Most often when a capacitor succumbs to
dielectric puncture, it does not short out completely.  A low-voltage DMM
will not notice the hole in the dielectric, unless the plates are pressed or
melted together to make a good electrical connection.  In a failed
oil-filled cap, they often aren't touching.

If you purchase used caps, you need to test them with a DMM _and_ a high
voltage power supply to know if they're any good.

-Adam
adamsmith-at-mediaone-dot-net