A while ago I obtained a G5 dual 2.7Ghz PowerMac with the intent of installing MorphOS. I currently run MorphOS on a G4 MDD so this would be a nice performance upgrade.

Initially, the G5 would run for about 10-20 minutes; the fans would then speed up and shortly afterwards it would shutdown. It ran like this for a few months. I intended to repaste the cpus and check the cooling system.

Before I could do this a new problem appeared. When attempting to start-up there was sometimes no response when the power button was pressed. Cycling the power supply switch would sometimes cure this new problem. I would then press the power button, the machine would start-up and then operate as described above, shutting down after 10-20 minutes. Pretty soon however, cycling the power supply switch no longer ‘cured’ the problem and when I subsequently pressed the power button instead I would hear a click followed by a second click from the power supply and then – nothing.

As far as troubleshooting, I have replaced the battery and reset the mcu. I have also removed/reseated memory, gfx card, HDs one at a time. My machine has the Panasonic heat exchangers. No leakage evident.

That is where I am at presently. The 2.7Ghz model takes a 600w power supply. I have tried a 450w supply. I was optimistic at first because when I pressed the power button, the machine immediately came to life, the fans came on – but after about 3 seconds it shutdown.

I have 2 questions for our G5 gurus:

1. Should a 450w Powermac power supply work in the 2.7GHz G5 or is it looking specifically for a 600w supply?
2. Any other ideas on troubleshooting or things I could look at?