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PowerMac G5 Won't Power On

617 Views 10 Replies Latest reply: Dec 1, 2012 7:42 AM by Matt Chach RSS
Matt Chach Level 1 Level 1 (65 points)
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Nov 27, 2012 8:32 AM

I have a PowerMac G5 from about 2004. Three years after that I got a laptop which I used as my primary computer. About a year after that I pulled the G5 out of storage and tried to power it up. It wouldn't start. I heard that it might have been the little 1/2AA lithium battery on the motherboard so I replaced that and voila! It worked. It went back in storage and I removed the battery, hoping it wouldn't be dead next time I go to use the G5. Well, the computer didn't turn on so I bought another battery. Still doesn't work.


The computer's power light just flashes once and it gives the tell-tale double "click-click" sound when I try to turn it on.


Is it possible the battery I replaced it with was old and not working? Bought it from RadioShack. Is there anything else I could do to try to get this computer up and working.


I was hoping to get it started so my Dad could edit some old home 8mm film footage that I'm going to digitize. 


Any suggestions would be tremendously appreciated. I did try holding the reset button on the motherboard as well, which didn't seem to do anything.



Powermac G5, Mac OS X (10.3.7)
  • BDAqua Level 10 Level 10 (114,805 points)
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    Nov 27, 2012 8:32 PM (in response to Matt Chach) 


    Double click sounds bad.


    Is there a red LED lit on the mother board when plugged in?

  • BDAqua Level 10 Level 10 (114,805 points)
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    Nov 28, 2012 7:51 PM (in response to Matt Chach)

    It sounds like the Power Supply, no red LED means no trickle voltage to start.

  • Jacumba Level 4 Level 4 (2,325 points)
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    Nov 29, 2012 8:43 AM (in response to Matt Chach)

    I'd focus back on the battery where it was the initial problem. Before purchasing another battery go to radio shack and have it tested they do it for free. Also if you purchase a new battery have it tested before leaving the store, it is possibly to recieve a bad battery, those type Mac batteries aren't a big seller and tend to sit around.


    Radio Shack sells them for $20.  Batteries Plus + sells them for $10, if you have one of those stores in your area. If you order one online there is no way to have it tested before it ships to you.


    Are you getting any fan running in the power supply when you try to start? It seems unlikely a power supply would up and fail while the computer was just sitting in storage with the power supply not getting any wear and tear or strain on it while just sitting doing nothing.

  • japamac Level 7 Level 7 (24,390 points)
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    Nov 30, 2012 5:41 AM (in response to Matt Chach)

    Double clicking PSU is almost always a dead PSU.

  • Jacumba Level 4 Level 4 (2,325 points)
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    Nov 30, 2012 6:25 PM (in response to japamac)

    In my expierence flashing lights and clicking would have to be fool proof, they are not. I wouldn't say ya buy a power supply. Is the fan running?

  • Jacumba Level 4 Level 4 (2,325 points)
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    Nov 30, 2012 7:47 PM (in response to Matt Chach)

    Power supplies are pretty cheap. The last one I bought was a 480 watt for $19. Cheap when you think a battery can run to that amount. A couple of things you can try is checking if the power supply fan has a dust build up or putting a small spray of WD 40 to get it going. It would appear to be strange that the power supply would fail while the computer in storage and did run before it was. Goodluck a power supply can be a tough call. Post back if you get it going.

  • japamac Level 7 Level 7 (24,390 points)
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    Dec 1, 2012 2:33 AM (in response to Matt Chach)

    If you have a volt meter (multi meter), you can test the PSU for trickle voltage.

    The process (for one) is discussed here: ml

    and here:


    If you do find no voltage issues and decide to replace the G5 PSU, you will have either a 450W, a 600W, or a 1KW (Quad only) model. The wattage is determined by G5 model.

    An example of the model applications (YES, I know these are expensive, but use as an information resource):


    Not a beginners proceedure, but retrofitting with ATX parts is possible: ml


    Do note that ATX PSUs do not have the same voltages as a G5 PSU, but, with some limitation, can be made to work.


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