John Robertson wrote:


As usual, heat is the enemy. Reading the technical specs for caps is
enlightening. They are rated usually at something like 2,000 to 5,000
hours at their rated temperature.

** Usually that number include operation at rated ripple current too.


So an 80C cap will die after something
like 2000 hrs at 80C

** I constantly see large can electros rated at 85C running operating in a 95C ambient that are 30 years old and still fine. Brand is LCR made in England, used in Marshall valve amplifiers and placed right next to the E34 output valves.


or 4000 hours at 50C and 10000 hours at 40C (not
looking it up!), whereas a 105C cap will last 10000 hours at 85C, etc.
So, the better the grade of cap the longer it will last in warm to hot
environments.

** 105C electros are pretty much industry standard these days.

Some of them last a long time and some do not.

It has more to do with ripple current and quality of manufacture than anything else.


And there is the equivalent resistance and inductance to
consider as well.

** Low ESR caps have proved to be the most unreliable of the lot - cos so many Asian makers got the chemistry wrong.

Inductance is however a non issue, electros of similar physical size and lead arrangement have the same inductance - usually not more than 25nH.


..... Phil