[Elecraft] Electrolytic Capacitor failure

[CUTTER DAVID]

Hello Gill
Doing reliability calculations to MIL 217 was very instructive many years ago and it taught me that operating well under the limits extended MTBF a lot.  Some military customers instructed that specs were 60% or more degraded to achieve longer service life.  What was your experience of that? It amazes me that amateur psus last so long!  Then, again, they are rarely continuously operated 24/7.
73
David G3UNA/G6CP

> On 16 April 2020 at 15:19 Gill via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> 
> As Harlan pointed out - I was an engineer for the FAA until retirement - 
> We changed electrolytics as part of normal PM's on critical systems 
> usually every 5 years or so. CDE (Cornell Dubilier) indicates expected 
> life (MTBF) of devices operated within rated voltage & temp specs to be 
> about 80-100 thousand hours. Most failures occur quickly around the end 
> of that period. For 24/7 operated systems, that translates to around 
> 8-10 years before rapid EOL failures begin to occur. Electrolytics can 
> be thought of like incandescent lamps - they have a finite useful life 
> and the fail quickly around the end of that time. ESR (Equivalent Series 
> (AC) resistance) increases which reflects in higher ripple currents in 
> power supplies are a main culprit. Check out: 
> https://www.cde.com/resources/technical-papers/reliability.pdf
> 73 Gill W4RYW
> 
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