Electrolytics

Tim Shoppa tshoppa at wmata.com
Mon Feb 23 12:25:29 CST 2009


>>> 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.

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.

Tim.





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