386 Motherboard Blown Capacitor, How Much Damage? Worth Fixing? \ VOGONS

386 Motherboard Blown Capacitor, How Much Damage? Worth Fixing?

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First post, by aberration

Posted on 2018-08-09, 01:11

aberration Offline

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So a good amount of the stuff I have found has been "liberated" from various municipal recycling sites and I recently obtained a 386 computer. When I went to power the old beast up there was a loud pop, some smoke, and then no display. Was wondering if I could get some advice as to if any damage has been done and if this is a board worth repairing. I managed to desolder the burnt-to-a-crisp capacitor and clean it up a bit and I'm hoping, since I can't find any, that there's no real damage done. The one that blew out is right between the ram slots and the AT power connector and I believe it is of the same variety as its now slightly blackened neighbor.

Thanks in advance for advice!

Reply 1 of 8, by The Serpent Rider

Posted on 2018-08-09, 01:32

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Most likely will be fine after recapping damaged one + neighbors.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 2 of 8, by Koltoroc

Posted on 2018-08-09, 01:47

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should be fine after replacing it. Tantalums tend to fail like that when they get too old.

Reply 3 of 8, by Mut

Posted on 2018-08-09, 11:15

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From my experience , if you replace only the failed caps , another one will blow up in the future. For safety I would replace all those tantalus with electrolytic caps.

Reply 4 of 8, by derSammler

Posted on 2018-08-09, 16:24

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Mut wrote:
For safety I would replace all those tantalus with electrolytic caps.

Actually, you better replace electrolytic caps with tantalum caps, not the other way around. Electrolytic caps can (and will!) leak, tantalum caps won't. And no, the way tantalum caps can fail is not an argument here, since that only happens when they are really old and don't get powered for a decade or so.

Reply 5 of 8, by carlostex

Posted on 2018-08-09, 17:07

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I've had a few tantalum explosions this year. One on an IBM 5160 board, a Paradise PEGA2 card, a Mediavision Thunderboard sound card among others.

Tantalums on IBM PC hardware are mostly 16v or 25v 10uf. These are really common. So i've been replacing on my hardware with these:

https://pt.mouser.com/ProductDetail/KEMET/A75 … kHVIs6y3Q%3D%3D

2 EGA cards after being recapped. I actually recapped my 286-16 motherboard with these capacitors. Tantalum capacitors are high performance, but nasty when they go boom.

Reply 6 of 8, by Mut

Posted on 2018-08-09, 18:07

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derSammler wrote:
Actually, you better replace electrolytic caps with tantalum caps, not the other way around. Electrolytic caps can (and will!) leak, tantalum caps won't. And no, the way tantalum caps can fail is not an argument here, since that only happens when they are really old and don't get powered for a decade or so.

Tantalum caps are not recomended anymore. Small value eletrolytics from good manufacturers will last decades before fail, are cheaper and will never fail catastrophically.

A good discussion about the pros and cons use of tantalums on eevblog:
https://www.eevblog.com/forum/projects/ ... ernatives/

Reply 7 of 8, by gdjacobs

Posted on 2018-08-09, 20:45

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Panasonic was recommending polymer caps instead of tantalum in most new designs. Given the small capacitance values involved, I doubt going polymer would be a significant step up in cost compared to appropriate low ESR lytics.

For details, see the attached application note (deals specifically with surface mount but through-hole applies equally).
https://www.element14.com/community/docs/DOC- … ts-for-tantalum

All hail the Great Capacitor Brand Finder

Reply 8 of 8, by aberration

Posted on 2018-08-10, 12:31

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As always thanks for the wisdom! Greatly appreciated!

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