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Boot Issue with Power Mac G5 (Dual 2.7GHz Model)

K

KMG1995

macrumors newbie
Original poster
Oct 11, 2014
6
0
Hello,

I've run into a brick wall with attempting to fix this G5. When I got it originally the radiator was leaking pretty bad, but by some miracle there was no damage to the CPUs or logic board. I ordered a replacement radiator from eBay, put new o-rings in it and booted the system up.

It ran perfectly, detecting both the CPUs with no problems other than Temperature Monitor reporting -30C for the first processor. I left it on for about twenty minutes and it ended up freezing. I could still see temperature monitor and the temperature of the second CPU was only ~ 42C.

So I turned it off by holding the power button, and then it wouldn't boot afterwards. Solid white power LED on the front and no red LEDs on inside. No chime or video output.

So I opened it up again and reset the PMU. But now--where I'm stuck at--it still won't boot, but now there's no solid white LED on the front. It only comes on when I push the power button. This has happened before, and I resolved it by taking out the PRAM battery for ten minutes. But no dice this time, it simply refuses boot or show a white light in the front. Does anyone have any idea what the issue might be?
 
KMG1995 said:
Hello,

I've run into a brick wall with attempting to fix this G5. When I got it originally the radiator was leaking pretty bad, but by some miracle there was no damage to the CPUs or logic board. I ordered a replacement radiator from eBay, put new o-rings in it and booted the system up.

It ran perfectly, detecting both the CPUs with no problems other than Temperature Monitor reporting -30C for the first processor. I left it on for about twenty minutes and it ended up freezing. I could still see temperature monitor and the temperature of the second CPU was only ~ 42C.

So I turned it off by holding the power button, and then it wouldn't boot afterwards. Solid white power LED on the front and no red LEDs on inside. No chime or video output.

So I opened it up again and reset the PMU. But now--where I'm stuck at--it still won't boot, but now there's no solid white LED on the front. It only comes on when I push the power button. This has happened before, and I resolved it by taking out the PRAM battery for ten minutes. But no dice this time, it simply refuses boot or show a white light in the front. Does anyone have any idea what the issue might be?
Click to expand...

Could be damage to the PSU from leaking coolant coming from the pumps.
 
I thought that too, but it wouldn't make sense seen as the system was apparently running fine before I was asked to repair it (minus the radiator issue) and after I repaired the radiator. There was never any random shut-offs nor has there been an instance where pushing the power button failed to engage the PSU.

My only ideas are a dead PRAM battery (don't have a multi-meter handy to check it) or a faulty logic board, but I want to make sure before spending the money for replacing one of those.
 
KMG1995 said:
I thought that too, but it wouldn't make sense seen as the system was apparently running fine before I was asked to repair it (minus the radiator issue) and after I repaired the radiator. There was never any random shut-offs nor has there been an instance where pushing the power button failed to engage the PSU.



My only ideas are a dead PRAM battery (don't have a multi-meter handy to check it) or a faulty logic board, but I want to make sure before spending the money for replacing one of those.
Click to expand...


Is there corrosion on the PSU cover?
 
As Altemose said, there is a possibility the power supply is shot. I suspect a bad processor, could be one or both, because of the negative temperature reported to Temperature Monitor. I have a LCS assembly that has *I think* dual 2.7 CPUs. If you are in the U.S., the assembly is yours for the cost of shipping. I can't guarantee whether they'll work or not, but there are no bent pins in the connector socket. I'm not trying to push my Mac junk off on you, I just figured I might be able to help.
 
Hmm, there's a bit of corrosion on the plate above the PSU, but I'll take that off and look closer tonight when I get a chance.

ctmpkmlec4 said:
I suspect a bad processor, could be one or both, because of the negative temperature reported to Temperature Monitor. I have a LCS assembly that has *I think* dual 2.7 CPUs. If you are in the U.S., the assembly is yours for the cost of shipping. I can't guarantee whether they'll work or not, but there are no bent pins in the connector socket. I'm not trying to push my Mac junk off on you, I just figured I might be able to help.
Click to expand...

Wow, thanks for the offer! If I can't get this worked out I'll be happy to pay the shipping to take your "Mac junk" off your hands. I live in north-western Pennsylvania.

But anyway, I'm not so sure it's the processors either because I have a second pair that came with the replacement radiator (which I verified to be working), and even those aren't working now.
 
KMG1995 said:
Hmm, there's a bit of corrosion on the plate above the PSU, but I'll take that off and look closer tonight when I get a chance.



Wow, thanks for the offer! If I can't get this worked out I'll be happy to pay the shipping to take your "Mac junk" off your hands. I live in north-western Pennsylvania.

But anyway, I'm not so sure it's the processors either because I have a second pair that came with the replacement radiator (which I verified to be working), and even those aren't working now.
Click to expand...
No problem! When doing the PMU reset, have you completely removed power by disconnecting the power cord from the power supply or wall socket? I know it's a pretty basic suggestion, but I know I am capable of sometimes overlooking the obvious. If you're sure the processors are properly seated and the RAM is properly installed, maybe check the connection between the power button board and the logic board. There is a short wiring harness that connects the two. If the LCS leaked before, it isn't unheard of for those pins on the logic board to be corroded. I hope you're able to get it going, and if you want LCS/CPU assembly, just send me a PM. Good luck!
 
I have a question for you, are there 2 red LED lights that turn on after awhile (one on each processor card)? My 2.7 did this for the longest time and ultimately I rebuilt the LCS and has worked fine until recently. Pressing the button inside the case next to the RAM got it to boot up a few times in the past.
 
No, there's no LEDs that come on if I let it sit for awhile. The fans just slowly rev up to full-speed.
 
Well I checked out the PSU: no corrosion anywhere on the case.

While I was in there I made sure everything was connected, but I took the time to examine the pins on the logic board & CPU, which I've yet to actually do:

http://imgur.com/a/SM7JE

The logic board pins just look like they have bits of dried up coolant on them, but it definitely looks like corrosion on the CPUs. Think this might be the source of the problem?
 
Yep, that corrosion would be an issue. Get some electrical contact cleaner spray from Radioshack to clean those pins. Clean both the CPU and logic board sockets and be careful to not bend the pins.
 
Okay, got the cleaner and got rid of most of the corrosion. Still not booting up and still no led on in the front. I noticed a couple pins seem to be severely bent or completely missing on the logic board, so I'm thinking I need to replace that since I've exhausted all other possibilities. Thankfully they don't appear to be too expensive on eBay.
 
KMG1995 said:
Okay, got the cleaner and got rid of most of the corrosion. Still not booting up and still no led on in the front. I noticed a couple pins seem to be severely bent or completely missing on the logic board, so I'm thinking I need to replace that since I've exhausted all other possibilities. Thankfully they don't appear to be too expensive on eBay.
Click to expand...

That is most likely the case. I hope you can get the parts at an affordable rate.
 
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