G4 will not power up. Help!

S

sarah12beetle

Registered
Here's a rundown of what I've got....
An Apple Quicksilver Power Mac G4
800 MHZ single processor
512 MB PC133 memory
CD-RW drive
Maxtor 40GB Hard Drive
I have been running machine fine with no problems, recently (2 months ago got the fan replaced as sheered off and made quite a racket) worked fine afterwards, but other day machine was switched off . Then I turn the thing on again and fans start to spin, the power light on the front stays on, but then the light goes out and the fans stop....
I tried resetting the PMU as I've read in other threads, but to no good.
Could the logic board be fried? Is it a lost cause?
I disconnected all the drives, monitor, etc. Tried powering up...the same symptoms as before; the fan comes on, then everything goes off. Like a car trying to crank, but can't quite get there.
Removed battery & replaced - Same thing.
Does this sound like a power issue to anyone? Or does it seem to be a logic board issue?
I took out the power supply and cleaned it thoroughly with canned air. Stuck it back in...same effect.
By now I just about know this thing inside and out( have taken apart everything but the logic board and CPU).

Please help
 
You can get any 350w or 400w ATX Power supply from about any where. Just look around. You should be able to find a 350 around $25.00 to $50.00 and a 400w goes for around $45.00 to $110.00. Just have to look around.
 
G4s do not use a standard ATX power supply. Pre-Gigabit models have a similar connector, but you need to change 2 wires (splice gray to orange and white to black...don't worry, it works). Later models use 22 pins and have a 28v DC pin for the ADC circuit that does not exist on any ATX supply. You will need to buy a new one, or shop on eBay for a used one or maybe a whole computer for parts. Hope this helps.
 
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