[mdlug] computer shutting down

[Michael Rudas (computer)]

-- Wolfger wrote:

> I mentioned in my DST post that my computer has
> been shutting itself off of late. Can anybody
> tell me how to diagnose this problem?

You likely have one of two problems, either of which
is usually due to bad electrolytic capacitors.

Check the capacitors around the CPU for physical signs
of leakage or swelling due to bad chemistry.  Here's a
couple of photos to show you what to look for:
<http://www.thenakedpc.com/dan/Bulging_Capacitors/close-up.jpg>
<http://www.careyholzman.com/caps/images/bad_caps.jpg>

and a good article on the subject-- at least *I* think
so... heh:
<http://www.daniweb.com/techtalkforums/thread910.html>

...and another:
<http://www.pcstats.com/articleview.cfm?articleID=195>

The same thing can happen with power supplies, as
well.  One of the useful indicators of this is to go
into the "BIOS Setup" screen (after the machine's been
on for a while) and check out the "Hardware Monitor"
page, which shows power supply voltages and CPU
temperature and (usually) CPU fan RPMs.  If the power
supply fan goes wonky or some of the caps are of the
defective type, the caps dry out or the supply burns
up.  Before this happens, the PS starts shutting down
and/or the volages start drifting out of spec (beyond
or below 5% of nominal on the 5V and 3.3V lines, 10%
on the 12V line), which causes a "power supply good"
(PSG) error and shutdown.

While you're in the hardware-monitor screen: if the
CPU fan slows down or the heatsink fins clog (most
common with thin-multifin copper heatsinks), the CPU
temperature can rise and the PC may go into thermal
shutdown.  Any CPU temp higher than about 45 deg C is
cause for concern.

Last-but-not-least, a simple fix that solves a lot of
problems: unplug and reseat the power-supply connector
from the motherboard.  Contact oxidation can occur,
and some of those pins carry up to 3-5 amps.

An issue to consider, if you are running Windows XP: a
new motherboard is considered a new computer, hence a
new ~$80 (or more) XP license is needed-- one of the
reasons I often replace the caps instead of the MB.

-- Mikey