Diagnosing PowerMac G5 failures

eric2006

iMovie Professional
Hello all,
I recently acquired two G5's, a 2.0 DP and 2.7 DP PCI-X PowerMac. Both were DOA, after inspecting both PSUs and reseating components the 2.0 started working, no luck with the 2.7.

When I plug the 2.7 in, the power light flashes and I hear a click. The same thing happens when I press the power button, but after pressing it once it won't click again for a few seconds or so. With the processor removed, nothing happens when I press the power button (on the 2.0 unit, the power light turns on while the button is pressed).
Also took the processors off the block and tried all 1/2 processor combos.

Obviously, the 2.7 has the LCS, so that was my first thought. I inspected the processor and found minor buildup, but not as major as http://www.xlr8yourmac.com/systems/G5_CoolantLeak_Repair/G5_CoolantLeak_Repair.html . There is no evidence of coolant anywhere else in the case.

I would like to get this fixed if possible, but am not sure if the CPU or logic board is bad, or both. Given the incompatibility of G5 logic boards with other processors I can't test that way. It's also possible I overlooked something.

I know the PSU is good after running it in the 2.0, also swapped pram batteries. I could swap the power button board but I think it's unlikely that that is the problem.

If all else fails, I may look for a broken 2.0, as I think the PSUs on those tended to fail?

Any insight would be appreciated, thanks

Edit 1: I swapped processors for kicks, the 2.7 will spinup but not chime with the 2.0 processors, which makes me think that the processors on the 2.7 are bad as it will not even spinup with them
 
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djackmac

ACMT
Pretty much if it gets down to processor or logic board with those its difficult to know without test parts. But in my personal experience, 9 out of 10 times its a bad processor or multiprocessor.
 

eric2006

iMovie Professional
Got new CPUs in for the 2.7, mounted them on 2.0 heatsinks to test before rebuilding the LCS. The system will power on and spin the fans (which it did not do before), but has no chime or any sign of life from USB hardware, or any display. Tried resetting the SMU, unplugging, replacing clock battery, etc. I ended up unplugging it and taking the clock battery out, will try again this weekend, but it looks like the logic board might be bad too.
Thanks for the help
 
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eric2006

iMovie Professional
Got the 2.7 up and running! Apparently, the pump needs to be plugged in for it to boot. I had the CPUs on air-cooled heatsinks, when I plugged the pump in it chimed and booted right away. Also noted that it needs to have some sort of heatsink to power on - I tried to test the CPUs without heatsinks and it would not turn on. I found some o-rings at the local hardware store, and picked up some hose clamps and fuel hose to rebuild the LCS as well. Using a mity-vac I was able to get the coolant throughout the loop without power. Re-calibrated the CPUs, and it's good as new.
 
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