G4 tower spontaneous shutdowns

For the past 10 days my G4 tower OS 9.1 has been shutting down spontaneously so after much research and no luck I finally took it into the Apple store. They put in a new battery, ran it for 4 days and it was perfect, passed all the tests. Brought it back to the office, ran fine for 6 hours then whamo! it shut down. I find that if I leave it off overnight it will usually boot right up in the morning, last a few hours, then whamo again. Like someone pulled the plug. I've tested all the in house wiring. Am connected to 2 strips and an APC 650. Everything else on the strip runs fine. HELP please. Any ideas anyone? Cheers and thanks.

might be overheating... can you verify that the fans are all working, and the CPU heat distributer is correctly installed?

Thanks for the reply. Everything has been verified by Apple Shop and ran smoothly for 4-5 days with them. Now it won't even boot up. Overheating made sense to me too but doesn't seem to be the case. Any other ideas?? I'm desperate here... cheers

macEfan said:

might be overheating... can you verify that the fans are all working, and the CPU heat distributer is correctly installed?

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As of this morning the G4 won't even boot. Until now it would at least chime before shutting down.. I've changed the power cable, the room is cool, have reset PMU, changed battery, run hardware disk and no problems... it's a mystery and am going crazy here. thanx

pripri said:

As of this morning the G4 won't even boot. Until now it would at least chime before shutting down.. I've changed the power cable, the room is cool, have reset PMU, changed battery, run hardware disk and no problems... it's a mystery and am going crazy here. thanx

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Could be your power strip. Any type of interruption or surge will do that. Happened to me last year.

mustang_savage said:

Could be your power strip. Any type of interruption or surge will do that. Happened to me last year.

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Thanks for the reply. I tried booting after disconnecting the HD but nothing. The button lights up but no reply, no chime. Just took it to the Apple store for a second diagnosis. How did you resolve your problem last year with the power strip? Bought a new one and the problem was resolved?
Again, thanks for the support.