My Mac G5 won't power up. Checked the cord continuity-good. Checked the power from the wall-good. Yet, when I press the button on the front of the box-nothing. Don't know if the problem is a fried power supply or the switch. I have a multimeter, can someone walk me through troubleshooting? Thanks.

Try holding down the power button on your G5. If that doesn't work, check that the button actually is connected to the computer. Yes- that means you will have to open up your computer, but it is a risk you might have to take.

I have the exact problem with my machine. Basically the power button has a loose connection. I give the front of the machine a hard slap with the palmof my hand and usually the power switch works. I've looked at the switch, but haven't got round to replacing it yet.