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Old 1st Dec 2017, 5:13 pm   #9
Argus25's Avatar
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,355
Default Re: Electrolytic capacitor fails after 1 hour in service!

Originally Posted by astral highway View Post
On inspection of the item when I had isolated it from the circuit, it performed normally up to 12V and then became progressively leaky, until it was passing 4A at a supply voltage of 30V.

This sort of thing doesn't surprise me as after seeing electrolytic caps fail in multiple ways so many times. In theory at least most of the high frequency ripple should have been bypassed by the 100nF. I guess for the replacement you could put a 1uF poly across it might help a little.

It is almost acting like a lower voltage part where the leakage is ok up to a certain voltage and suddenly goes up over that. It is possibly a miss labelled part or very bad quality clone part.

I'd also be cautious applying 30v x 4A or 120W to the the capacitor for more than a second or two, it will heat up pronto and explode its rubber seal and spray its guts all over the room.

A 63V rated cap seems like a very safe margin for an 18V supply, probably not much point in going to a 160V one, sometimes the higher voltage ones have a slightly higher ESR which is not helpful. And as noted a high ripple current rated one would help.

What does it read on the ESR meter ?

Last edited by Argus25; 1st Dec 2017 at 5:18 pm.
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