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Level 2

308 points

G5 shuts down suddenly, does not reboot anymore

Hi,

I was just surfing the web, suddenly G5 shuts down, as if you would pull the plug.

If I press the power button, it won't reboot. I hear the apple startup chime, and about 5 seconds later, it shuts down again.

Nothing appears on the screen.

I've done this already:

- open the lid, removed some dust

- try to boot with all other hardware disconnected

- try to boot from FW800 lacie external HDD, with a recent clone of my system drive (made with Carbon Copy Cloner)

- take out battery for half hour

no results, still startup chime - then dead.

So I guess:

it should be a hardware error, since it won't boot from the external FW drive.

So it is probably the power supply or the motherboard.

correct? any other suggestions, that I can try before taking it to Apple repair service?

( I had a dead powersupply in 2007 in the same machine, costed me +300 euro)

Any help is appreciated.

Regards, A.C.

 G5 PPC dual 2GHz (june 2004 model) / 3.5GB RAM, Mac OS X (10.4.11)

Posted on Sep 1, 2011 12:51 PM

21 replies

--A--C-- Author

Level 2

308 points

Sep 13, 2011 9:17 AM in response to BDAqua

Do you mean I need to take apart the CPU units as well?

Screw the PCB from the heatsink?

Cause now I can't see any thermal paste.

seems risky business to me. Have never applied thermal paste, it is a delicate job probably?

worth the risk, when I'm not sure if that's the problem?

BDAqua

Level 10

239,369 points

Sep 13, 2011 9:54 AM in response to --A--C--

It's harder on a G5 than most any other computer.

See if you can get it to run long enough to...

Get Temperature Monitor to see if it's heat related...

http://www.macupdate.com/info.php/id/12381/temperature-monitor

And/or iStat Pro...

http://www.islayer.com/apps/istatpro/

If you have any temps in the 70°C/160°F range, that's likely it.

--A--C-- Author

Level 2

308 points

Sep 13, 2011 9:55 AM in response to --A--C--

Another thing I'm considering, why has it worked for one day by blowing dust out?

Isn't that an indication that the problem is not thermal paste related?

BDAqua, you mentioned in your first answer also the graphics card, could dust on there also cause these symptoms?

(And, how can I mark this thread as unsolved? Or do I need to start a new thread?

because not many people will do an effort reading solved questions)

--A--C-- Author

Level 2

308 points

Sep 13, 2011 9:58 AM in response to BDAqua

The G5 shuts down approximately 5 sec after pressing the button.

I don't even get anything on my monitor.

I do use and check temperatures regularly on both my computers with iStat Pro, and didn't notice anything unusual prior to the shutdown, also not when it worked for one day, temperatures normal.

cpu temps in the range of 55°C

--A--C-- Author

Level 2

308 points

Sep 29, 2011 1:11 PM in response to BDAqua

Yesterday evening, I replaced the thermal paste of the processor cores.

Took me a while, 'cause I wanted to gather as much info as possible on the subject, and had to wait for the delivery of the Arctic Silver 5.

For those interested, started another thread on the subject here:

https://discussions.apple.com/thread/3344773

But too bad: the G5 remains dead. It doesn't even give me the startup-chime anymore, if I press the power button nothing happens at all. So It must be the power supply after all. Or else I did something wrong without realizing, but I think I did everything perfectly.

Anyhow, I don't want to buy a new PSU, guess I'll be saving up money for a new Mac Mini then.

Thanks all for your time and suggestions!

Oct 1, 2011 12:21 PM in response to --A--C--

The service manuals have information on how to measure/verify the PSU. Only needs a voltmeter.

Some have used an ATX PSU as a replacement:

http://damntechnology.blogspot.com/2009/02/rebuilding-powermac-g5-power-supply.h tml

The following thread is also quite informative:

http://forums.nekochan.net/viewtopic.php?f=9&t=16720839

G5 shuts down suddenly, does not reboot anymore