Replacing motherboard capacitors

Just tried powering up an old (386) PC, and was greeted with an acrid smell and a puff of smoke; one of the motherboard capacitors had blown. I'd like to try replacing it, but my main concern is: what rating should I buy as a replacement? The surviving originals are all marked "10+ 16J".

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John Elliott
Reply to
johne
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10 microfarads @ 16 volts (just a guess).
Reply to
Charles Schuler

they are tantalium caps, replace with another tantalium.

Reply to
inty's world

I'd replace them with electrolytics unless there's very good reason why tants are essential. As they smoked I'd assume they're across the supply, ie filter caps, so as long as they physically fit, electrolytics are a reasonable choice for replacement.

Tantalum caps have very high failure rates, and worse still they often fail short circuit. I never use them unless I have to.

Dave

Reply to
Dave D

The last PC I had do that - the PSU regulation had failed!

Reply to
I.F.

That's a 10 uF 16 volt tantalum cap. They tend to be very reliable, but when they do fail, they short and smoke. A tantalum cap would be best, but any decent 10 uF 16 v cap should work in that application.

There's no need to replace any other caps if only one failed. This isn't like the more recent motherboard that were made with dozens of defective caps.

As a quick test, you can try removing the cap. Chances are the PC will at least POST without it.

When you replace it, note that the stripe on a tantalum cap identifies the positive side, but most other caps have the stripe on the negative side. Andy Cuffe

snipped-for-privacy@gmail.com

Reply to
Andy Cuffe

I did this (using a known good power supply) with mixed results. It looks as if the -12v line is shorted to ground somewhere, because the power supply refuses to switch on if it's connected. If I disconnect

-12v and leave the other power lines connected, the board powers up and makes it through POST.

I think I'll let the matter rest, at least for now.

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John Elliott
Reply to
johne

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