24 Jul
2007
24 Jul
'07
1:05 p.m.
Thanks, everyone, for your helpful responses! I'll definitely test the
power supply out with a dummy-load, just need to run out and get some
parts when I get a chance. It does appear to run fine with no load
whatsoever, and the voltages it's putting out look to be correct under
those circumstances.
My _guess_ is that the PSU is OK, and that the real fault is a
short-circuit from one of the power lines to ground somewhere in the rest
of the computer.
Have you tried doing a DC resistance check from each power line to
ground, on the mainboard with the PSU disconnected? In other words, leave
the PSU out, and check the resistance from each of the power pins to the
ground pin on the connector where said PSU conenctes.
Can you build up the machine in sections (even if it can't boot like
that)? Conenct _just_ the mainboard first, then add things like the
keyboard, disk drive, expansion cards, etc. In case the shoet is in one
of those.
What's the best method for testing for bad capacitors?
Sicne there will be many in parallel, unfortunately, you have to desolder
each capacitor and check is separately. In general, the capacitors that
fail are the electrolytics, both the aluminium and tanatalum types.
Start by doing a DC resistance check to see if they're dead short. Then
use an ESR meter (Effective Series Resistance) to find those that have
'dried up'
-tony