[avahifi]

My iMac G5 died.  It will run for about 5 minutes and then shut off like you pulled the power plug.  I have been told it is either the power supply or logic board going south.

How easy is it to replace the power supply?  Anyone know of a good source for the necessary parts?  Replacing the logic board probably is not a cost effective choice.

Thanks,

Frank Van Alstine

[Bigfish]

Frank:

Check out Tiger Direct to determine if they have what you are looking for.  If nothing else it will provide you with an idea for prices.  http://www.tigerdirect.com/

Ken

[jaywills]

Sorry to hear your news.  My G5 2.0 ghz dual tower just died three months out of warranty ("It might be the processor, or it might be the logic board.  We won't know until we replace them at ~$1K.").

A source for parts I've used before:  http://www.mac-pro.com/

From my reading, there are a significant number of G5's that develop overheating problems.  The only sound from Apple is crickets chirping.  Good luck.

[soewhatman]

I don't know how Macs are built internally, but a buddy of mine recently had a similar problem with his PC.  It turned out the heat sink on the CPU had come loose and was no longer making good contact.  The CPU would overheat and the computer would shut itself down.  I don't know if this problem would be possible in a Mac.

Rick.

[andrewbee]

Certain models of the G5 iMac had power supply issues, particularly the earlier models. If it restarts after it shuts down it may well be a power supply issue. Some of the power supplies show this behaviour mode until they finally will not restart. Sometimes you can also detect a faint burning odour.

[Andrikos]

It definitely looks like a thermal shutdown issue.
Make sure your processor fan is not dead.
If it is, it's an easy $5-$10 fix.

good luck.
PS Also make sure it's not caked with dust.

[avahifi]

The problem turned out to be a defective power supply module.  I was able to find a new replacement for about $100 and R&R myself with no problems (three screws, one plug in connector).

It turns out Apple did have a three year extended warranty on that part for my machine as there were lots of failures from my series of iMacs.  Unfortunately, the warranty was three years and mine was four years old.

The job was easy enough to avoid the high labor rates at Apple and other repair shops. And of course I did get the upgraded supply to avoid a repeat of that problem.

Frank Van Alstine

[andrewbee]

Good to know you got it sorted out. The early G5 iMacs are actually pretty good, certainly much easier to work on than all the others that have followed. The original G3/G4 iMacs are even better if you don't need the processing power.
Some of the the electrolytic caps in the p/s are run close to their rated voltage and eventually swell, fail and sometimes when they fail pop open with a bang.

Andrew

[santacore]

Glad to hear this got sorted out. I have a iMac G5 that's been sitting for years because I didn't know how to fix it. People I've talked to said it was either the power supply or the logic board. Basically the unit would work fine once you got it powered on. But anytime you would turn it off or restart it, you would roll the dice as to whether it would boot up again. Most of the time I'd get a white screen and nothing else. Sometimes it took 10+ restarts before I could get it to boot properly. I finally gave up on it and it's been siting ever since. Maybe I should try the power supply replacement. Of course it's a $100 gamble. Tough call.

[andrewbee]

If you get a white (grey) screen everytime you restart its not the p/s.
Reseat the memory.
Try booting from the startup cd in the optical drive. Hold down the "c" key before or right after the chime to boot from the optical drive.
If it boots consistently then its either your HD / OS.
Next step.
You can reinstall the OS by using the same CD and performing an "archive and install" preserving your user and network settings.
If all is well then you are back in business.

If you have an external drive with an OS try booting connected via firewire.
You have to hold down the alt / option key (keep holding it down) before or right after the computer chimes and that will bring up a screen which allows you to select the startup volume (you can let go the key now). Select the external firewire drive to startup from.

If it still does not boot from either the optical or external drives then disconnect the internal HD and try again.

Of course it could be the logic bd or something else but going from your description (white screen) it sounds like the OS is not loading.


Andrew

[krikor]

Glad to hear this got sorted out. I have a iMac G5 that's been sitting for years because I didn't know how to fix it. People I've talked to said it was either the power supply or the logic board. Basically the unit would work fine once you got it powered on. But anytime you would turn it off or restart it, you would roll the dice as to whether it would boot up again. Most of the time I'd get a white screen and nothing else. Sometimes it took 10+ restarts before I could get it to boot properly. I finally gave up on it and it's been siting ever since. Maybe I should try the power supply replacement. Of course it's a $100 gamble. Tough call.

My 3.5 year old G5 tower (dual 1.8ghz processors) just bit the dust with similar symptoms.  Intermittent booting until it would boot no longer.  Kernel panics. No boot from the OS disc.  Could boot from the hardware test disc, but the test showed no hardware problems.  Finally had our company's mac service look at it, who told me it was a bad logic board and that the paltry sum of $900 could fix the problem.  Even if I wanted to attempt the repair myself, the cheapest logic board I've found is nearly $800.  No thanks ... the computer was $2k new and I can get a more powerful mini for less than the repair cost.  I also found a website that surveys Mac users for reliability and found that my particular model had an 19% failure rate on logic boards.