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PowerMac G4 (MDD) won't turn on - HELP!

I've just bought a PowerMac G4 (MDD) Dual 1Ghz off eBay.

Connected it to my ADC monitor and power, pressed the power button and... nothing.

The power light comes on while I'm pressing it, but that's all.

I opened the machine, removed the RAM and tried it - nothing. I reseated the RAM and tried again - nothing.

I swapped the battery - nothing. I pressed the Reset PMU button for a few seconds - nothing.

I plugged in an old keyboard with a power button on it - but that did even less than pressing the button on the machine.

I have noticed that very occasionally a couple of lights on the main board come on for less than a second.

Occasionally the fan on the fold-down door will spin for a second.

I have tried to remove the main power cable to clean it, but I couldn't get it off the logic board. Instead, I lifted it as much as possible and then reseated it. That seemed to make the lights come on slightly more often and the fan spin a bit more - but I cannot be sure.

I've contacted the seller and asked if they had any problems - and not heard back at all.

The eBay description for the item shows it running, so I really hope it's nothing I've done (I'm sure that plugging it in and connecting it to a monitor shouldn't harm it!) but I really want to get it working, rather than my only other option - strip out all the useful parts and then try to sell what's left on eBay to try to recoup a bit of money.

Am desperate for advice that isn't just "Sounds like the PSU is dead" because those things are rare and usually more money than I paid for the whole stinking machine. PLEASE HELP!

Posted on May 28, 2011 3:19 AM

Best reply

Texas Mac Man

Level 8

46,839 points

Posted on May 28, 2011 6:02 AM

Resetting the Logic Board

Resetting the logic board can resolve many system problems. Whenever you have a

unit that fails to power up, you should follow this procedure

before replacing any modules.

1 Unplug the computer.

2 Press the Power On button on the front of the unit.

3 Open the side access panel.

4 Remove the battery from the logic board.

5 Wait at least 10 minutes before replacing the battery.

6 Make sure the battery is installed in the correct +/-

direction.

7 Reassemble the computer and test the unit.

Note:

This procedure resets the computer’s PRAM. Be sure to

check the computer’s time/date and other system parameter settings

Power Mac G4: Computer Does Not Power On, No Fan Movement

http://docs.info.apple.com/article.html?artnum=95038

 Cheers, Tom 😉

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18 replies

Apr 12, 2014 4:38 AM in response to Richard Tanner

in case someone reads this...

the problem was the processor one of the two died.

I bought a second hand one on ebay and the comp works it still has some minor issues though

BDAqua

Level 10

239,363 points

Apr 12, 2014 10:40 AM in response to OS 9.1 is the best!!!

Great to hear, thanks for the report! 🙂

Nov 22, 2016 6:56 AM in response to Richard Tanner

I had the same problem on my G4 1,42 dual processor. I got a lot of replies saying all the usual things.

The best answer I ask was on YouTube which would suggest the mother board has either some microscopic cracks in the tracks of the mother board ~ or some faulty components on the mother board. The poster of the video solved the problem by buying a replacement mother board and he got his computer working again after rebuilding it with the new mother board.

People will bang on about disconnecting the computer and holding the power button in for several seconds, or resetting the power management switch, or even taking out all the PCI cards but I can tell you from my own experience that none of the work.

I was not prepared to fork out for a new mother board so I sold mine for parts

PowerMac G4 (MDD) won't turn on - HELP!