iMac G5 locking up

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Level 1

11 points

iMac G5 locking up

My iSight G5 iMac quit working a couple of years ago and I haven't been able to part with it. It always turned on fine, but would lock up after a couple of minutes. The Genius Bar told me I had a bad logic board, but never took apart. After reading many stories about bulging capacitors, I finally took it apart and was surprised to find no bulging capacitors on the logic board or power supply. I did notice the power supply has several "beads" of black silicone-like material between various capacitors. It does not look like the pictures on the internet of the same model # power supply. If it is the power supply, why does it turn on and remain on?

I now have a gutted G5 in my computer room and am unsure of what to do next. I had a place lined up to replace the bad capacitors when I took it apart for <$100, but am now doubting this is the problem. Will the Genius Bar test a logic board and power supply not in the case? Any other ideas? Could it be the battery? Do not really want to sink any more money in it since you can buy a much more powerful Mac Mini for $500 more.

iMac 24 2.66 Core 2 - Macbook 2.4 Core 2, Mac OS X (10.6.2)

Posted on Jan 5, 2011 9:22 PM

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Answer 1

spudnuty

Level 5

7,116 points

Jan 5, 2011 9:52 PM in response to MacSkoog

MacSkoog,

It always turned on fine, but would lock up after a couple of minutes.

Have you looked at the console logs?
The power supplies fail in these and can cause a lockup (easily repairable) and more rarely the GPU (not easily repairable or repairable at all (got one here I've been trying to repair via GPU replacement but so far no luck in removing and replacing a GPU w/o destroying it)).
Richard

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Answer 2

MacSkoog Author

Level 1

11 points

Jan 6, 2011 5:27 AM in response to spudnuty

Unfortunately, it is laying in pieces and I cannot even turn it on, much less check the logs. I did reset the PRAM during testing, but this was all done a couple of years ago and I am getting fuzzy on what testing I did. It is very consistent about locking up in just a few minutes, but the screen doesn't go blank or blink, so am surprised that it could be the power supply.

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Answer 3

MGW

Level 7

27,041 points

Jan 6, 2011 7:14 AM in response to MacSkoog

Have you ever replaced the battery? Is there any dust in the air vents or on the fans? It;s very difficult to attempt to diagnose a computer in pieces, best you take it in and have the logic board tested.

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Answer 4

spudnuty

Level 5

7,116 points

Jan 6, 2011 8:35 AM in response to MacSkoog

MacSkoog,

It is very consistent about locking up in just a few minutes, but the screen doesn't go blank or blink, so am surprised that it could be the power supply.

Right, so that sounds more like a GPU problem.
Which iMac iSight is it? CPU speed, size?
Richard

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Answer 5

MacSkoog Author

Level 1

11 points

Jan 6, 2011 9:20 AM in response to spudnuty

The iMac is the last model that came out before the Intel's. It was a 1.9ghz G5 with 512mb Ram and 160gb hard disk that had Tiger, since update to Leopard. It had the 17" screen and built-in iSight camera. I have never replaced the battery. It is relatively clean inside and was not overheating.

When you other folks found out your GPU was bad, how did you know? Will the Genius Bar test the logic board out of the case or did you find out via the hardware diagnostics disk?

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Answer 6

MGW

Level 7

27,041 points

Jan 6, 2011 12:20 PM in response to MacSkoog

The genius will test the board, but they do it behind closed doors, so I'm not sure if it needs to be in the case or not. My guess is it doesn't need to be installed.

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Answer 7

MacSkoog Author

Level 1

11 points

Jan 6, 2011 1:16 PM in response to MGW

Nope, they won't test a logic board that is not installed. I just called the Naperville store and got that answer.

Another interesting thing about the iMac G5 is that I can start it up in Target Disk Mode and connect to it with my other iMac. It stayed running long enough for me to write zero's to the hard drive which was several hours. When it was in TD mode the fans all went to high, but when I boot it normally, the fans stay at normal speed if any.

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Answer 8

spudnuty

Level 5

7,116 points

Jan 6, 2011 8:32 PM in response to MacSkoog

Hey MacSkoog,

It stayed running long enough for me to write zero's to the hard drive

Hmmm try downloading and running Temperature Monitor:
http://www.bresink.com/osx/TemperatureMonitor.html
to see if an overtemp problem in the CPU is your problem.
Richard

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Answer 9

MacSkoog Author

Level 1

11 points

Jan 19, 2011 5:08 PM in response to spudnuty

I am suspicious that it may be the graphics processor. I downloaded the temp sensor program and the warmest thing being monitored is the gpu and it locked up at 50.6 degrees celsius. It shows the graphics processor ambient air at 47.6c. Incoming air is 22.5c. The cooling fins on the gpu are so hot that I cannot put my fingers on them for very long.

Is it possible that the gpu is the problem, and if so, is that repairable?

I ran the same program on my black Macbook and the hottest thing is the wireless module at 42c, everything else is in the thirties.

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Answer 10

spudnuty

Level 5

7,116 points

Jan 20, 2011 7:17 AM in response to MacSkoog

MacSkoog,

If it is the power supply, why does it turn on and remain on?
the warmest thing being monitored is the gpu and it locked up at 50.6 degrees celsius.

That doesn't seem very hot given that the upper limit on the ALS CPU is 85ºC.
So it's back together? To quote myself:

Have you looked at the console logs?

The iSight that I had that had a failed GPU wouldn't even produce video out.
Richard

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Answer 11

MacSkoog Author

Level 1

11 points

Jan 23, 2011 5:22 PM in response to spudnuty

I am about to give up. I fired it up and ran it for almost en entire hour, watching the temp the entire time. I did a software update the entire time and constantly moved the mouse. I don't know if this made a difference or not, but it ran the entire time until the software update wanted to reboot. The hottest thing this time was the memory controller which got up to 82.6c.

The console did not have anything in it. I don't remember what it said, but something to the effect of language set to english, etc. I believe there were only 2-3 lines of information in the console. Nothing said about errors or failures.

Now, the G5 will not startup up at all. The light comes on bright the entire time and after a several second, all fans go on high. I have tried turning off and on all day with the same effect. The screen remains black the entire time and no startup charm at all.

Don't know if keeping the thing on for an entire hour finally fried something, but I have now gone backwards. About ready to take it apart and sell it for parts.

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Answer 12

May 21, 2011 10:43 AM in response to spudnuty

Sorry for off topic. I think I've tracked down Spudnuty as someone who rehabs old Macs and donates to schools. Anyone have a link to a website so that I may contact him? I have two iMac G5s that he may be able to salvage into one for donating.

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Answer 13

KSkid

Level 1

0 points

Aug 13, 2011 9:52 AM in response to spudnuty

I am also looking for Sudnuty to donate an iBook.

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