# Power Mac G5 not powering up properly



## sabbertonic (Jan 12, 2012)

I have a Power Mac G5 Desktop 2Ghz- M9032LL/A  serial number XB4060FBNVS. I bought it June 26 2004.
I use a power strip that I turn off after the computer shuts its self down. 
The failure mode that has occurred before and now seems permanent is:
Power strip on. I hear the relay in the computers power supply click on then off. 
Push power button: it lights up while I'm holding it but it does not stay lit. I hear the fans come on and the hard drives spin up BUT no chime and no display.
I hold power button 5 sec and it powers down.
I measured the internal 3.6 volt battery in circuit at about 3.5 volts. Since it was the original I replace it with a new battery that I pretested under a 1ma load. The unit powered up normally and I reset the clock. Had a normal 4 hour session with no problems. Next day it was back to the same power up problem. I verified battery voltage at 3.6 volts in circuit. Tried several power up /down cycles.
I tried to reset Pram
I reset the PMU as instructed on MAC site. Same problem.
On the my test bench with nothing connected it repeated these same symptoms. After several attempts I did get it to chime 2 power cycles in a row but I did not have a monitor hooked up. So I powered it down by holding the button 5 sec. When I hooked up the monitor and rebooted it failed to chime.  I removed the monitor and it has failed to chime since then. 
I have removed both hard drives and replaced them with a spare.  I have tried to boot up with no hard drives. No change. The power supply is obviously not totally dead but maybe one of the voltages is intermittent? Plug 1, pin 1 of the power supply does have 5.1 volts in standby mode. Does this sound like a logic board problem?
I have tried reseating the video card and RAM.
This is my main music studio computer and I need it to work. Any help would be greatly appreciated.


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## gsahli (Jan 13, 2012)

Are there any diagnostic LEDs on that motherboard?
Have you reset the cuda chip?
http://support.apple.com/kb/HT1939


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## sabbertonic (Jan 14, 2012)

gsahi,
Are there any diagnostic LEDs on that motherboard? 
No
Have you reset the cuda chip?
I did reset the PMU button which is the cuda on a G5


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## gsahli (Jan 14, 2012)

sabbertonic said:


> I did reset the PMU button which is the cuda on a G5



Sorry about that - I thought I had edited that to say "Oh, ya, the cuda IS the PMU."

I think you're at the point where the only way forward is to try replacing the power supply, and if that doesn't fix it, you know it's the motherboard, and that isn't worth replacing for a powerPC.

Review this:
http://www.badcaps.net/forum/showthread.php?t=14628

One source of power supplies (check eBay, too):
http://www.dvwarehouse.com/PowerMac-Power-Supply-c-247_5371.html


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## djackmac (Jan 14, 2012)

More than likely a weak processor...Or, occasionally vibrations from normal operation can unseat the processors from the base on the logic board. Try reseating the processors.


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## sabbertonic (Jan 16, 2012)

First, thank you for your help, I greatly appreciate it.
Let me just summarize so far in order what I've done,
Summary of failure;
Power strip on. I hear the relay in the computers power supply click on then off. 
Push power button: it lights up while I'm holding it but it does not stay lit. I hear the fans come on and the hard drives spin up BUT no chime and no display.
I hold power button 5 sec and it powers down.
Replaced 3.6 v battery and measured it in circuit, 3.6v.
Reset Pram
I reset the PMU as instructed on MAC site.
Removed hard drives, disconnected monitor 
Reseated the video card, RAM.
Removed lower processor (after I marked it) and tried to run it on one processor
Removed upper processor and reinstalled it
Tried lower processor only in upper position
Measured all the voltages on P1 (24 pins) and P2 (16 pins) of power supply while it was connected and powered  up after no chime. All voltages were correct on all pins. 25v,12v, 5v, 3.3v, -12v. (I have a pinout diagram.) Could not get to P3 8pin connector. Is this a fan supply?
While I measured these voltages the plastic air deflector was out. The fans came on full and a red led came on by power button
Tried the lower processor in the upper position
All of these attempts failed to get a reliable power up. Three times I did get a chime on power up but next time it would fail to power up with a chime.
Before I give up and call the logic board bad can I try to power this computer up without the video card installed?
With no video card, no hard drives,  should I still get a chime on power up?


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