Todd Lyons wrote:
>Steven Lawrance wrote on Thu, Nov 08, 2001 at 07:50:43PM -0800 :
>
>>Since I'm just a software person and not an electrical engineer, a bad
>>capacitor means that I'll have to probably replace the motherboard,
>>
>
>Having been an electronics tech in a previous life, I can verify that
>electrolytic caps are a problem that gradually onsets. We used to get
>boards in that before we would even start checking parts, we would
>change all the electrolytic caps. The standing rule was if it's not
>been changed in less than 6 years, change it without question. Flaky
>caps on power supplies were the #2 most prevalent fix. (#1 was bad
>gate driver or base driver circuits, depending on if it was DC or AC
>equipment).
>
>Caps most frequently "dry out" in warm ambient temperatures. And it
>really is drying out. If you open a new cap and compare to an old cap,
>you'll see that it's much less moist. That also contributes to it
>getting warmer (and is mainly why they burn up...no moisture). I'd
>consider inside of a computer running for several years to be warm
>ambient temperature.
>
>Your mobo could very well be doing this if it's been in service for
>4 or more years.
>
>Blue skies... Todd
>
Generally you will see a residue (brownish) around an electrolytic cap
if it has gone
bad. That is the electolyte (dieletric) between the foil leaking out.
Replacing all of
them if less than 6 years is rather hard core and is the shotgun
approach. The only
reason to do that is if you #1) Don't know what the real problem is and
don't have the
tools to troubleshoot it. or #2) Work at a business where it is more
cost effective to
replace them all rather than pay labor cost to troubleshoot the problem.
Also lot of times the layperson will have more trouble finding the exact
cap to replace
than just replacing the board.
I'd look for leaky caps and if you don't see any residue, consider
moving your troubleshooting
else where.
