VOGONS


Tantalum capacitor value

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First post, by dionb

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Tantalum caps, the little fireworks you love to hate.

This one failed short on an So4 board so needs replacing.

The attachment PXL_20241228_214642535.jpg is no longer available

Question is: what with?

The markings are "10" and "16". That 16 sounds like a 16V part, but it's the 10 I'm not sure about.

Would that be 10uF?

And given it looks like a simple filter cap, would a ceramic replacement be OK or should I go for low ESR aluminium or tantalum electrolytics?

Reply 1 of 2, by Deunan

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10uF / 16V. Note that polarity on those is marked differently, the positive lead is marked. This one has a + so it's easy to tell but even a dot or a strip, which might look like -, is the positive end. Get it wrong and watch fireworks again.
There are no ceramics that go that high except MLCCs and these have their own issues when biased with DC (loss of capacitance), plus these days nobody makes anything but SMD. So your options are electrolytics - tanatalum, aluminum or perhaps polymer. Tantalum are longer lasting but prone to cracking with thermal cycling, esp. the older ones. Modern tantalums, if not some cheap no-names, will last. But you can install something else if tantalums make you nervous. However if that is a 12V line I would suggest getting 25V rated caps, I've seen plenty of old tantalum caps fail but 95% of the time it's a 16V cap on 12V line. There is such a thing as a max dV/dt with these and modern higher power PSUs can easily overstress the older tantalums with too fast voltage rise on power-on. Higher voltage rating caps will have higer limits, and are usually a bit bigger but 25V one should not be that much different (and modern caps are usually smaller in general).

Reply 2 of 2, by dionb

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The cap was on the 12V line near an ISA slot, so the 25V tip is a good one.

The thing that makes me nervous about tantalums is the failure mode - aluminum fail faster, but they fail open and frequently do so visibly. Open fails tends not to damage other stuff, shorts does. That said, this cap lasted the better part of three decades. I seriously doubt I'll be doing this stuff with this board 30 years or more in the future...