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I'm repairing my old 478 socket computer motherboard and two 6.3v 2200uF capacitors near the CPU are bust. The computer still powers on, but it doesn't pass the BIOS screen without the ps/2 mouse plugged in, and the keyboard stops working after about 20 minutes.

I'm wondering if I could replace the broken 6.3v 2200uF caps with 16v 2200uF ones instead?

TheJamaicanGuy
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    Yes, you can. 6.3V is the minimum required voltage. – Circuit fantasist Feb 22 '15 at 21:47
  • Yes if you have the required space. Do not leave long connection pins, and put a tinny drop of hot glue to secure capacitor shell in to the PCB. – GR Tech Feb 22 '15 at 21:53
  • Those are Low ESR caps. If the 16V cap fits in the space of the 6V3, its ESR is almost surely too high to be of use. Caution: High ripple current may cause it to overheat and blow up in your face. – Turbo J Feb 22 '15 at 22:48

3 Answers3

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Yes. The voltage rating of a capacitor is the maximum it can take. In theory, a 16 V cap is a superset of a 6.3 V cap if the other specs are the same.

Olin Lathrop
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Yes, but ... .

A 16V 2200 uF capacitor will provide the same capacitance as a 6.3V 2200 uF one.
It should work properly - initially.

Added:
[[ Spehro notes that the capacitors should be low ESR (equivalent series resistance) parts. It's likely that caps with an adequate ripple current rating will also have low ESR as the two are related. ]]

A 6.3 V capacitor of the same capacitance MAY have a higher ripple current rating - the amount of current at operating frequency that it will tolerate long term. In a power supply situation this is likely to be the case and is reasonably likely to matter. (ie ripple current rating is a factor in cost and designers tend not to over-design $ wise if they can help it.)
A capacitor run above its ripple current rating will run hot, dry out quicker and die sooner. If the capacitor dis it MAY do more damage than when it first fails - but probably not.

Aluminum electrolytic capacitors should be run at 80%+ of their rated voltage for longest life. Not liable to matter too much here.

Russell McMahon
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    "Aluminum electrolytic capacitors should be run at 80%+ of their rated voltage for longest life. Not liable to matter too much here. " that means more than 80%? I always thought it was better to have a safety margin, and the parts themselves may be +- 20% – user2813274 Feb 23 '15 at 07:09
  • @user2813274 >~~= 80% is a figure that I've seen stated by some manufacturers. I had a look through past SE answers of mine and found a claim by me to that effect **BUT** the most excellent reference (party on dudes) that I cited in it disagress with me :-)/. The reference is worth looking at. It contains graphs from some utterly awesome and long lost experimental paper which they do not cite afaics. || [Myanswer](http://electronics.stackexchange.com/questions/17048/does-the-voltage-across-an-electrolytic-cap-significantly-alter-its-lifespan/17050#17050) .... – Russell McMahon Feb 23 '15 at 10:12
  • @user2813274 .... [Awesome reference](http://www.tayloredge.com/reference/Electronics/Capacitors/ElectrolyticLife.pdf) = http://www.tayloredge.com/reference/Electronics/Capacitors/ElectrolyticLife.pdf – Russell McMahon Feb 23 '15 at 10:13
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If they will physically fit, probably not.

You must use low impedance (low ESR) capacitors on a motherboard. Ordinary 2200uF 16V caps will not work properly and could cause something to be damaged if it isn't already.

Spehro Pefhany
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    Interesting the various perspectives. I suspect in a motherboard supply that large ecap ESR will not be a stability issue (but, I may be wrong), but higher ESR translates into more heating and lower ripple current rating, so this part of our answers tends to share common territory while they are not identical. – Russell McMahon Feb 23 '15 at 04:13
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    @RussellMcMahon I base this on personal and anecdotal evidence that carefully replacing bulging capacitor plague parts does not always restore functionality- I've not attempted to analyze why this is so, but I can imagine wild swings in output voltage resulting. I agree the answers are somewhat different, and I can't say that anything is actually wrong in any one. – Spehro Pefhany Feb 23 '15 at 06:49