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PowerMac G4 Quicksilver won't turn on

My Dad owns a PowerMac G4 Quicksilver 867Mhz computer, with default parts installed, and no add-ons whatsoever. He was using it one night, and it was running fine, and then the next day, he tried to turn it on, and it wouldn't do anything. The light stays on while you're pushing on it, but turns off as soon as you release it. I have tried all the following:

CUDA Switch: Tried a dozen different diagnostic test with this switch, none worked.

Power Supply: Bought a fine new working power supply, switched them out, didn't work.

PRAM Battery: Took a brand new PRAM battery and put that into the computer, didn't work.

Power Cord: Switched out the old power cord with a fine working one, didn't work.

So after all that, what on earth can I do now? If I have to replace the Logic Board I can, but I'd be very surprised if it was the problem. We had no storms, no power surges, no "brown-outs" or anything that would disrupt or damage my Dad's computer, so I'm at a loss as to what it could be. If anyone has any ideas, EVEN if I've already tried them, please post. Thanks.

Power Mac G4 933 Mhz Quicksilver 2002, Mac OS X (10.4.10), 512MB RAM/60GB HD/128MB VRAM GeForceTi4600

Posted on Apr 8, 2008 6:55 AM

Top-ranking reply

Limnos

Level 10

419,875 points

Posted on Apr 8, 2008 7:06 AM

Well you tried a new PRAM battery, but did you test it? I once had somebody give me a computer with a new battery (saw him take hte old one out and put the new one in) and the new battery was dead. If you have a digital multimeter you can check the condition of your present battery. It should read at least 3.2V if it is the 3.6V half-AA battery type. Ideally this should be measured while the battery is under load; added recommendation from Hans777:

I have recently found out that an exhausted battery will still indicate >3.6 V with a high internal resistance VM.

Checking incircuit: powercord disconnected press PMU reset button for >about 5 sec before measuring.

Checking outside: load the battery with a 1500 Ohm resistor when measuring.

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20 replies

reslar

Level 1

0 points

Jul 2, 2008 6:12 PM in response to Jan Olsen1

I'm in the same boat guy's. Battery tests out at 6.34v. I know some apple tecs who I can beat on, hopefully I can get back with some answers.

Jul 30, 2008 1:22 PM in response to infestedsmith

Based on everything posted and the following components verified OK:

PRAM Battery is at approx. 3.6v
Power Supply has trickle voltage of 25v at pins 11 and 22
PMU switch S1 has been reset

I would recommend replacing the motherboard, retaining the original CPU. I know people are reluctant to replace the motherboard, but they do occasional fail. Hope this helps, good luck.

Jul 30, 2008 4:50 PM in response to Chris Dunn

Chris Dunn-

How did you decide on the Motherboard over the CPU module?

Aug 18, 2008 6:15 AM in response to Grant Bennet-Alder

Has anyone had to replace the power supply? I have tried all of the above with my dead Power Mac. Replaced the battery, waited 15 secs., etc., etc. I really need this computer back up
and running yesterday. Since it is an eight- ⚠ year-old computer, where do I find a power supply in a hurry?

Aug 18, 2008 7:00 PM in response to Michael Brugh

Replacing the Power supply absent smoke or burnt smell is a bit drastic. Have you looked for the Trickle Power voltage on one of the unique-colored wires at the main DC wiring harness?

If you do not find a 5 Volt or 25 Volt trickle power there (with AC power cord plugged in but mac nominally OFF) eBay has power supplies from G4s almost every week.

PowerMac G4 Quicksilver won't turn on