[atFault]

Dual 450 G4, 1 Gig, 80 Gig (9), 40 Gig (X), A105 DVD, Radeon 9000 64M, Nexus 128 32M.

No recent changes to the machine except adding a firewire cable for iPod(3G) syncing, but it had that months before (1G) with the same setup.

Would start up and run fine for a while and then go to sleep. Immediately it would cycle as if it was doing this: sleep, wake, sleep, wake, sleep, wake, etc., about every second. Force shutdown and the restart it would do the same thing and not even boot up. I let it 'cool down' for about an hour and then started it up again. It ran but could not find any HDs and you could not hear the drives spinning. It would run fine from CD though, but still didn't see HDs even with disk utility. There is no USB power load and no ADC power load either.

Pulled the drives and both worked in another machine. Pulled the extra vid card and left one drive in the G4 (X) connected the power to the wiring loom that would normally be for the Zip drive, and started it up. It has since run for 48 hours.

Are there two 'sections' to the power supply? One for optical and Zip and one for HDs? Can a power supply begin to fail and not be able to handle as much load as before?

Any help would be greatly appreciated.

atFault

[Macola]

I'm not sure if you can have partial failure, but here's an easy way to test your power supply if you have access to a multimeter:

http://docs.info.apple.com/article.html?artnum=95064

[Detrius]

Have you tried resetting the PMU? (Power Management Unit) It's a portion of the logic board that controls everything power related from power on to reboot to sleep to spinning up your hard drives. Since your machine is failing to go to sleep, this is most likely going to fix it:

There is a button on your logic board. Shut the machine off. Pull the power plug out of the power supply. Push the button only once. Wait 15 seconds. Plug the box back in and power it up. If you have anything in PRAM, it will be lost (RAM disk). You will have to reset your date & time.

If this does not fix it, you likely have a bad motherboard, not power supply. Your battery may need replacing due to this. If the battery is dead, PMU reset will not work. Radio Shack caries the battery. 23-026 (1/2AA, 3.6V Lithium).