On Jan 3, 2011, at 12:55 PM, Leo Hoyt wrote:
I have a dual 2.7 Ghz PPC G5 w/ 4.5 GB ram. The machine recently started powering off without warning. Is this signs of a power supply failing?
I don't think this is necessarily a sign the power supply is failing. I have a dual 2.3 that had a power supply fail. It was NOT part of the batch of G5's covered in the Extended Warranty program for G5's with defective power supplies, it was manufactured 3 weeks too early for the program, and I'm almost certain yours would have been covered in this program except for the fact that it ended in January 2010, so you're too late for a free replacement (unless you already got it replaced free?).
When mine failed with less than 1 week usage it failed instantly with the smell of burned electrical components and no startup after that. Testing with a multimeter yielded that more than half the power sources were dead. Since this Mac was brand new I was somehow able to talk Apple into replacing the power supply for free. They also replaced the entire logicboard and both CPUs, which they do send back for "re-certification" to be used in future warranty or replacement work if they're still good.
The symptom you're describing is something I still have intermittent problems with. I'm almost 100% certain it's got more to do with power line fluctuations rather than a failing power supply. I've noticed that on several occasions when my G5 suddenly powers off without warning that this power off is accompanied by some other event. Examples of other events that I've noticed occurring simultaneously with the G5 power off are 1) a washing machine motor starting. 2) a refrigerator compressor starting 3) a furnace motor starting 4) a slight dimming of all incandescent lights. I've worked hard to isolate my G5 from these power line fluctuations, it's on its own circuit breaker, has its own UPC, but neither of these has helped enough to stop these intermittent power-off instances. It happens about once every couple weeks or so, and always powers up again instantly without problems other than those related to the power-off. My UPC DOES seem to catch about half of these power-off cycles, BUT, it's a royal pain- in-the-ass because when the UPC catches the glitch it has an alarm, a high-pitched shrill alarm, and the alarm turns off when you press a button, BUT pressing the button results in an instant power-off of the G5, so you can't just press the reset on the UPC, you first must Shutdown the G5 and then reset the UPC, so it nearly defeats the entire purpose of the UPC. When I'm gone, the alarm has bothered my pets for 8-12 hours at a time. About half the times the UPC alarm doesn't sound at all, and the G5 just "stops" cold, one second fine, the next off. The monitor and other hardware don't seem affected by these power line glitches, only the G5 itself.
If so how hard are the power supplies to replace in these towers?
I believe it's very difficult. They're expensive also. Apple wanted over $800 for their work on mine, and that's what the warranty receipt said, something like $875 in total work, with the power supply unit being near $400 I think?
Your G5 is different than mine. Mine is air-cooled. Yours is liquid- cooled. Yours should have came from the group covered in the extended warranty. People say that you really need to watch for corrosion in the liquid-cooled G5's. They also say that you should never power-off a liquid-cooled G5 because this is what causes the corrosion. The is anecdotal evidence from schools and businesses that have large quantities of liquid-cooled G5's running and they noticed that the ones that were never powered-off didn't have problems with leakage or corrosion. The idea is that by having the fluid always circulating and always at constant temperature there's no corrosion, but when it stops circulating and cools on a daily basis this causes corrosion and leakage. I don't know if anyone has added automotive radiator stop- leak additives to their coolant in a G5, but it might not be a bad idea if you see any signs of corrosion and still have a working power supply unit. My understanding is that as soon as they start leaking the power supplies blow once they get wet at all. Once they blow, they don't startup again. If your G5 is still starting after these intermittent power-off events, it's NOT a blown power supply, and mine has been having these events for several years now without any other problems. I'm almost 100% certain my problem is caused by power line voltage or amperage drops of some sort rather than anything specific to a power supply failure. When then fail, they don't startup any more.
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