G5 iMac Will Not Turn On - Power Supply Diagnosis?

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Level 1

6 points

G5 iMac Will Not Turn On - Power Supply Diagnosis?

My A1145 20" iSight PPC G5 iMac will not turn on - it doesn't respond to the power button. It had been shut down for a few days, I turned on the power and it booted up as normal, the desktop appeared and I was about to open the web browser when it suddenly went dead; the screen immediately turned off with no warning or noise. There is no fan or disk noise coming from it when the power lead is plugged in, just a very, very faint electronic hum from inside.

From reading various webpages, it seems possible that the power supply could have failed. Is there a simple way that I can diagnose this before deciding whether to attempt to replace it myself or not? I understand that there should be some diagnostic LEDs which could help identify a problem - I've removed the surround from the iMac and peeled back the black EMI film below the display but I'm not sure for what or where I should be looking (they seem to be easier to find on the 17" models).

Whilst I know a repair might not be cost-effective on such an old machine, I have 220GB of photographs, documents and music on it - none of which is backed-up - so I am very keen to get it working and backed-up as soon as possible.

Could anyone suggest how to diagnose the problem?

iMac G5

Posted on Nov 6, 2013 5:24 AM

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Answer 1

K Shaffer

Level 7

34,966 points

Nov 6, 2013 3:06 PM in response to JoeBloggs

Hi there:

My experience with Macintosh computers has not included the G5 iMac even though I almost got one to replace a failed-under-AppleCare iMac G4 17" 1.25GHz after three/four major failures and no local support.

...So, I think you may be able to pull the hard disk drive out of that computer and see if an external enclosure could allow you access those files IF the drive spins up at all. Sometimes odd things happen, and the G5 iMac had some history of capacitor and other failures that could be a problem. I see there are a few free information guides here that may be helpful: http://www.ifixit.com/Device/iMac_G5

If the battery on the logic board was dead, but the computer kept in running condition by leaving it plugged in, once the computer was left unplugged for a time then the device may fail to start. There is a way to reset the power management chip (different names for same idea as technology moved forward) and that could help in the process of troubleshooting most power related issues in the PPC Macs of later G3/G4/G5 design.

There are troubleshooting items of interest in here http://www.apple.com/support/imac/g5/ ie: what to do when your computer won't turn on...

Sorry to not be of direct help in this matter.

Good luck & happy computing! 🙂

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Answer 2

JoeBloggs Author

Level 1

6 points

Nov 7, 2013 3:48 AM in response to K Shaffer

Thanks - I've seen the ifixit guides (useful if a bit daunting - 49 stages to swap the power supply ...). Unfortunately the Apple help page re diagnostics doesn't apply to the iSight model.

I don't think it's the battery on the logic board (PRAM?) as the machine booted up fine and then died.

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Answer 3

Klaus1

Level 9

52,749 points

Nov 7, 2013 4:18 AM in response to JoeBloggs

Anything here help?

iMac G5: Fails to startup

http://support.apple.com/kb/HT2173?viewlocale=en_US

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Answer 4

JoeBloggs Author

Level 1

6 points

Nov 7, 2013 3:26 PM in response to Klaus1

Thanks - doesn't apply to the iSight versions of the G5

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Answer 5

Feb 10, 2014 4:54 PM in response to JoeBloggs

I wanted to add my story because until the end, my situation was the same. But it ended up differently.

Everything from the initial humming and a slight caustic smell coming from the top left corner of my 2010 iMac made it seem like the power source was failing. When my computer wouldn't turn on, the LEDs confirmed the power source was not working.

HOWEVER, when the Apple tech opened up my computer, they said my computer was really dusty. I mean, the vent slot is pretty wide and probably lets in a lot of dust. The dust was preventing my computer from booting up, not a failed power source. From now on, I'll use the dust cover on my iMac when I'm not using it. I should have been doing this from the beginning. Whoops.

Apple didn't charge me for opening up my computer, even though it was no longer covered by Apple Care. In addition, replacing the power source would have only cost me a little less than $110, including parts, labor, and tax.

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Answer 6

Feb 10, 2014 4:56 PM in response to JoeBloggs

I posted this on a similar question, but I wanted to share it here too.

I wanted to add my story because until the end, my situation was the same. But it ended up differently.

Everything from the initial humming and a slight caustic smell coming from the top left corner of my 2010 iMac made it seem like the power source was failing. When my computer wouldn't turn on, the LEDs confirmed the power source was not working.

HOWEVER, when the Apple tech opened up my computer, they said my computer was really dusty. I mean, the vent slot is pretty wide and probably lets in a lot of dust. The dust was preventing my computer from booting up, not a failed power source. From now on, I'll use the dust cover on my iMac when I'm not using it. I should have been doing this from the beginning. Whoops.

Apple didn't charge me for opening up my computer, even though it was no longer covered by Apple Care. In addition, replacing the power source would have only cost me a little less than $110, including parts, labor, and tax.

Reply