iMac shuts down for no reason

Hi all,

My iMac G5 (10.4.10) keeps on turning off for no reason. I'll walk away
from the computer, come back an hour later, and it'll be shut down. It
almost always happens when I'm not using it, for whatever that's worth.

About 2 years ago, the same computer would shut down every time it went
to sleep. Apple replaced the power supply and that solved the problem.

This time, there doesn't seem to be any connection to sleep mode. I've
left it asleep overnight, and it's still been on in the morning. On the
other hand, I know it's shut down minutes after I walked away from it,
when it was still awake.

I've run disk repair and the hardware test since this started happening,
and both showed no problems.

Does anyone have any thoughts about what this might be? Is there
anything on the computer that I can check for clues (logs or anything
like that)?

Thanks for any help you can offer!
-ez

 

I was afraid of that. At first I thought it wasn't the computer but
the electricity flickering in my apartment, but I'm pretty sure that
isn't the case now.

Is it a coincidence that the same thing started happening to

Strange coincidence. If you can post what the results are, that would be
great. Sadly, my iMac is about one week out of AppleCare. I just moved,
and I really don't want to splurge for a new computer.

I don't think that's the problem in this case, but I'll double-check.
Thanks for the help!

 

It still might need a power supply. This generation of machine is
probably embraced in the ongoing free repair program:

http://docs.info.apple.com/article.html?artnum=302181

m.

 

Thanks very much! I'll check that out.
-ez

 

It turns out my computer is still AppleCare eligible (until Monday--that
was close!), and also that the free repair program ends after 3 years,
when AppleCare ends.

Anyway, I called AppleCare today after my computer shut down twice in 2
hours, once in the middle of running Disk Repair of the OS X DVDs. The
woman had me disconnect all peripherals (speakers which are always on
and printer which almost never is) and reset the PMU. It hasn't shut
down since then; it's been about 2 hours. I hope that solves it, but I'm
skeptical.

 

Have you reconnected all the peripherals?

 

Nope. I never did reconnect the peripherals, and the computer still shut
down twice in the past hour. I'm bringing it to an Apple-authorized
service provider, hopefully tomorrow.

Oh well. I've already had to replace the power supply on this computer
twice, the hard drive once, and one other part whose name I'm forgetting
once (it was the longest and most challenging one of them all).

-ez
-ez