Roy J. Tellason
rtellason at verizon.net
Mon Feb 23 23:39:47 CST 2009
On Monday 23 February 2009 01:25:29 pm Tim Shoppa wrote:
> >>> I have to say, for all the talk of failing caps in power supplies
> >>> I've only ever seen one electrolytic cap fail *ever*, and that was
> >>> last week in a one-year-old graphics card that has hardly ever been
> >>> powered off...
> > Gordon, you don't mention how many caps you've looked at or tested, or
> > how you've done so, but I encounter them constantly. Not so much in
> > the 1980's vintage DEC equipment YET, but it's no myth that AEC's are
> > electrochemical vats that have a lifespan. The lifespan varies widely
> > depending on many factors, heat being the big one.
> My gut feeling is that electrolytics got a lot lot better in the 70's
> compared to earlier generations. It's not just that they're 20 years
> newer than the ones from the 50's, they really were better
> quality to begin with.
Having worked with stuff starting out with junk made in the 1950s and earlier
and onward, I would agree with this.
> I work on old radios and it's pretty much a given that any set has
> electrolytics in need of replacement. If the set was used for a while,
> in fact some lytics were probably already replaced in the 50's or 60's, and
> maybe the replacement needs replacement today.
> "Failed" is a relative term... it's easy to find electrolytics leaky
> enough that they no longer meet their original spec, or leaky
> enough that they get warm. But the set still works.
> Other times they literally explode, or they cause other components
> in the circle to fail catastrophically... my experience is that
> switching supplies are far more sensitive to out of spec ESR's
> in electrolytics than any old radio ever was.
Yes. I've done a number of those, too. A bit of hum in an old radio isn't
necessarily a killer, and it's amazing sometimes how bad those old parts can
be and the radio still seems to work. :-)
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