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Old 2nd Dec 2017, 4:41 pm   #30
Al (astral highway)
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Join Date: Nov 2006
Location: London, UK.
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Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Andrew2 View Post
My money's on it being incorrectly marked, either voltage or polarity-wise.

Andrew, I think so, too. It seems to be behaving like a 25V or 16V device. I think even 25V rated would blow quickly on the DC bus, feeding that chip, quite a noisy environment, so probably a 16V mislabelled as 63V.

I may contact the manufacturer to see if this has happened before. I still don't feel it's appropriate to name them as the provenance is murky, not from what we would recognise as a trusted electronics wholesaler but an EBay business. They were described as low ESR, 105 degree C rated.

Quote:
Originally Posted by Argus25 View Post
What this really shows is that it is possible to make good electrolytics, but they cost a lot more $, that Rifa cap is not cheap. So we are looking at a situation where electros are being made down to a price, not up to a standard. With all the different competing companies making them, trying to undercut each other on price, it is not really surprising that there are so many poor quality electros around. A simple case of you get what you pay for perhaps.
Hugo, a very interesting point. And indeed, since individual electrolytics, even the lower voltage ones, are so expensive, there's an incentive to clone them at a dirt cheap production cost, charge top dollar and make £8 profit a pop. Far more, obviously, for the 380V big ones that are sought after by audiophiles.

I'll take a look at Rifa's from now on. I haven't used tants for years, and I didn't know that they could be good enough for mil service, so that's both interesting and reassuring. I have seen them as decoupling caps on many DC buses on big old boards with multiple chips on them, from the early 80s, but have never tested them to see if those particular ones still work to spec.
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