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Re: [Amps] LK-500

To: amps@contesting.com
Subject: Re: [Amps] LK-500
From: Steve Thompson <g8gsq@eltac.co.uk>
Date: Tue, 17 Jan 2006 16:53:57 +0000
List-post: <mailto:amps@contesting.com>

dick.knol@planet.nl wrote:
> Rich Measures AG6K sells 450 WV 105ºC electrolytic caps for HT PSU use. 
> (http://www.somis.org/Price-Info.html)
> 
> Please note that contrary to crack, a 105ºC rating electrolytic cap 
> cannot be obtained on every street corner. However, the 105ºC rating 
> will result in a much longer servbice life in a hot HFF power amp 
> environment.
A while ago I looked at the ratings on Philips electrolytics, where you 
can get physically identical capacitors, one family with 85C rating, the 
other with 105C rating. For the same value, the ripple current ratings 
were different, as were the lifetimes at the operating temperatures.

I worked out the thermal resistance from the maximum allowed temperature 
and I^R rating at 85C. Working backwards to 105C, I ended up with 
exactly the ripple current specified for the 105C part. The different 
lifetimes were related in just the same way. In other words, these 
appeared to be absolutely indentical, just specified at different 
operating temperatures. I don't know if there's any manufacturing 
difference between 105 and 85C parts - but it would not surprise me if 
they all come off the same conveyor and just had different part numbers 
printed on them.

I've not tried it for other brands but I can imagine the same might apply.

Steve
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