My G4 Quicksilver went dead with the following symptom. The power button lights up when pressed, then goes off when the button is released. A tiny light on the motherboard flashes momentarily but nothing starts in the computer. A Mac "Tech" said it was a bad Power Supply so I obtained a replacement and carefully made the changeover. It still exhibits the identical same symptom so I am assuming it is not the power supply. Does anyone have any idea what might be the problem. Getting Mac service here in Montana is very expensive with questionable results.
Thanks for any suggestions
Replace the battery that sits on the logic board. Available from Radio Shack at around $16.
Further steps to follow when you have completed this one