Fixing a mac

Chip Fixes, Thu Jul 14 2011, 09:17PM

ok so I did a google search but I couldn't find much.
I am trying to fix my friends Powermac g4 which apparently worked fine yesterday but now when you hit the power button the led light behind it stays on until you stop pressing own the power button, then it dies. And nothing else works, no fans run or anything. i already checked the power supply and it works so I think it has something to do with the motherboard?

EDIT: never mind I think it is the power supply, it's having a shorting problem
Re: Fixing a mac
Conundrum, Sun Jul 17 2011, 06:12AM

I have a few mac bits around here..

Look for any bulging capacitors in the power supply, this could be your problem. If found replace with spares, ideally new but at a pinch any old low ESRs such as ones from a fairly new PC power supply might work.
Also have a look for the startup circuit, it could be that one of the divider resistors has gone O/C or changed value.
Many "dead" PSUs can be fixed in this way if nothing else has fried.
I usually run mine from a series connected light bulb in a socket to see what that does, thanks Sam G's FAQ !

If all else fails you could do what I did and attempt to make a generic power supply, 8 power bricks in parallel later and the LCD TV worked enough to see that ordering a PSU would be a cost effective repair smile

Its still working!!!!!


Or you could go down the DIY route and... Link2

-A