Diagnosing a Quad G5 that won't boot or chime

[ziggy29]

I just got hold of a cheap Quad G5 to mess with, since I've kind of always wanted to get my hands on a G5 and play with it. Was told it was working perfectly well, but when I plug it in, hitting the power button does nothing. When I remove the plastic shield inside the case, the fourth LED (Trickle) glows amber but *no* other lights come on. No chime, no boot, no nothing.

I have pressed the SMC reset below the bottom RAM module, to no effect.

Any G5 veterans seen this? Could it be a power supply issue (keeping in mind it's getting at least some power because the trickle light is on)? Would a dead PRAM battery possibly cause this? Bad RAM? (Some of this I doubt because it might cause other LED status lights on the board to glow.) I have a fairly generous window to return this thing but if it's something simple I'd rather try to deal with it myself than ship this behemoth back. I've never had a G5 so I'm not really familiar with its troubleshooting.

 

[AphoticD]

I just got hold of a cheap Quad G5 to mess with, since I've kind of always wanted to get my hands on a G5 and play with it. Was told it was working perfectly well, but when I plug it in, hitting the power button does nothing. When I remove the plastic shield inside the case, the fourth LED (Trickle) glows amber but *no* other lights come on. No chime, no boot, no nothing.

I have pressed the SMC reset below the bottom RAM module, to no effect.

Any G5 veterans seen this? Could it be a power supply issue (keeping in mind it's getting at least some power because the trickle light is on)? Would a dead PRAM battery possibly cause this? Bad RAM? (Some of this I doubt because it might cause other LED status lights on the board to glow.) I have a fairly generous window to return this thing but if it's something simple I'd rather try to deal with it myself than ship this behemoth back. I've never had a G5 so I'm not really familiar with its troubleshooting.

It does sound like a power supply issue. Does the front power-on light illuminate when you press the button?

You might want to pull out the LCS, CPUs and power supply, check for leakages, clean connectors and reassemble to reseat things. Even just check that the PSU connections to the logic board are all well connected.

Download and step through the G5 (late 2005) Apple Service Manual at

http://tim.id.au/laptops/apple/powermac/powermac_g5_late2005.pdf

There should be some helpful troubleshooting steps to try and also voltage pinouts for the PSU.

 

[ziggy29]

Thanks. Looked through some of those already. Just a few minutes ago, I took out all the RAM, then with the battery I took it out, reseated it, and rotated the PRAM battery in the socket and it chimed and started to POST up. Problem is, then I turned it off and after that, it wouldn't start again. And once in a while, when I plug in the power cable, even without pressing the power button, it would POST up again, chime would come, fans would kick in.... but the power button isn't triggering it. The only lights that stay on are light #3 being red and #4 being amber, which seems like normal operation.

As for pulling stuff, I don't want to do too much because I can still return it for a while (assuming it's worth the return shipping) and if I tear it down and can't get it properly back together, that option is out. I'll start with a new PRAM battery and diagnosing/reseating other connections. Also wondering about the quality of the power cable, and wondering if it consistently providing enough juice, since powering up sometimes seems intermittent based on plugging and unplugging that power cable.

 

[ziggy29]

Update. I think there are some issues with power management itself on the board, maybe? Yesterday for the first time, I got the G5 to boot and be usable. I had to play a lot of tricks -- take the battery out and unplug for a while, put the battery back in, reset the SMU, press the power button a few seconds, plug in and then press the power again -- I think that was the sequence, and then it booted up. I used it for a while and it was stable.

But when I powered it down, it wouldn't start up again when pressing the power button. Unfortunately I suspect there is a problem on the logic board somewhere which might not easily be resolved.

 

[0248294]

I'd start disassembling the unit to look for any potential water damage, the Quads are known the spring a leak. If there is any water damage on the logic board and/or processors, it might explain the fact the G5 is being temperamental.

 

[ziggy29]

I'd start disassembling the unit to look for any potential water damage, the Quads are known the spring a leak. If there is any water damage on the logic board and/or processors, it might explain the fact the G5 is being temperamental.

Thanks. So far I've seen no evidence of leaks, but I haven't done much of a teardown yet. I also suspect failing caps on the PSU are a possibility, based on what I've been able to ascertain so far.

 

[XaPHER]

Have you tried reseating the graphics card? I almost tossed my 2ghz late 2005 before doing so. If laying the machine on the floor (with opened case facing the floor) doesn't reveal any liquid, LCS leaks may not be the problem.