PowerPC G4 starts to launch, then shuts down

[LoNicot]

My desktop G4 has been working great for years. I recently powered down, then when I powered up, fans turn on, I get the chimes, the grey apple screen, the spinning wheel, then, a minute later, the fans turn off and the whole thing powers down.
With a safe boot, it has the black screen with white lettering and says several things like (forgive me for not being exact - it happens fast) "can't complete .... " and has a few screens of this, then pauses, then says "killing all processes" "cpu done" and powers down again.
I've tried booting from the install disk, and it powers down again. I've removed all peripherals, including extra memory and extra usb ports, same thing. I've plugged into different outlets, same thing. I've reset the little PMU switch, same thing. The little battery measures 3.6V.
Any advice would be appreciated.

[Lil Chillbil]

bad cpu is what it sounds like to me

[PowerPCMacMan]

I think what the problem could be is a faulty power supply.. What G4 do you have? If you have the MDD, then it could be a faulty Front Power Module.. I suspect PSU at this point.

If the CPU was the problem, nothing would come on... no grey screen, no Apple, no chimes, nothing... or you could still get chimes, but a series of chimes, I think 5 of them which means: PROCESSOR IS UNUSABLE.

[DarkSel]

Originally Posted by Lil Chillbil

bad cpu is what it sounds like to me

It sounds more like the CPU is overheating.

If it was the power supply, the machine would not be able to stop all processes before shutting down.

[MisterKeeks]

Originally Posted by DarkSel

It sounds more like the CPU is overheating.

Yeah, I think you are right. It doesn't appear to be an issue with anything until the CPU has heated up.

[LoNicot]

Thanks for all the input.
So, if the CPU is overheating, how do I prevent it from doing so? All the fans seem to be working.

[MisterKeeks]

Originally Posted by LoNicot

Thanks for all the input.
So, if the CPU is overheating, how do I prevent it from doing so? All the fans seem to be working.

You can reapply heatsink paste- Google it, you'll find tutorials.

[rabidz7]

Originally Posted by LoNicot

Thanks for all the input.
So, if the CPU is overheating, how do I prevent it from doing so? All the fans seem to be working.

This might not be worth it, but a liquid cooling system would work wonders. But you can just reapply heatsink paste. If applying thermal paste does not work, then it is time for a new fan or liquid cooling system.

[Lil Chillbil]

Originally Posted by rabidz7

This might not be worth it, but a liquid cooling system would work wonders. But you can just reapply heatsink paste. If applying thermal paste does not work, then it is time for a new fan or liquid cooling system.

a liquid cooling system on a g4 would not be a good idea

however I have jerryrigged many a fan system on a g4 using super glue and a clearence fan from fry's electronics

[Zotaccian]

Does the situation change if you disconnect the hard disk and then try to boot from install disk?

[MisterKeeks]

Originally Posted by rabidz7

This might not be worth it, but a liquid cooling system would work wonders. But you can just reapply heatsink paste. If applying thermal paste does not work, then it is time for a new fan or liquid cooling system.

A liquid cooling system would offer no improvement over air cooling whatsoever. With proper air cooling the system runs fine, so why take the risks of liquid with no possible gain?

[rabidz7]

Originally Posted by MisterKeeks

A liquid cooling system would offer no improvement over air cooling whatsoever. With proper air cooling the system runs fine, so why take the risks of liquid with no possible gain?

It would run cooler and that would make the entire system last longer and it would allow for overclocking.