PowerMac G5 Quad can't boot, overtemp and checkstop led light up

[giathyex]

I have a PowerMac G5 Quad

I install a pair of 2GB DDR2-800 Corsair XMS2 Ram in the right slot (mirrored centermost)

At first, I got 3 beep and the fan start to spin fast
After some re-seat and change ram module, I got the boot chime

But a few second after the chime, overtemp led bright up, and led806 checkstop bright up too. It stucks at it and the fan start to ramp up faster and faster. No display

So my G5 should be still alive and that is just some problem with the liquid cooling unit? Should I spend time to clean and rebuild the cooling unit?

Thank you for help

 

[amishallin]

I recently acquired 1 of these on ebay. However, mine acts slightly differently. It boots into Tiger and is usable for a few seconds before the CPU overtemp and checkstop LEDs (#2 and #7) come on and it locks up. What's interesting is I can long press the power button to shut it off and turn it on again with the same result. Changing the power setting to "reduced" gives a couple more seconds of usability before it overheats.

There are a few things I plan on doing in the spring.
1) Perform the "new blood" mod on my version 2 liquid cooler. This will be done outside due to the degrading toxic coolant in the loop. There should be other mods out there for version 1 coolers.
2) Repaste the chip on the back of the logic board (northbridge?) since that seems to be an issue with overheating if the plastic mounting clips melt and the heatsink comes off (or heatsink fins are clogged). This sounds like a possible design flaw. May also find a better way of mounting the heatsink and add an aid filter of some kind to the front.
3) Repaste whatever chip is under the large black heatsink on the front of the logic board.
4) Repaste the CPUs.
5) Do a deep clean of the whole system (incliding all heatsink fins and fans) while its in pieces.
6) Ditch the previous owners original hard disk with an SSD and a fresh OS install.

Until then I have the computer laying on its side on a table with the side panel off so if it does leak it won't (hopefully) get on the power supply.

May try documenting this on youtube. Don't think there are any videos like this yet and don't have experience with making videos.

 

[giathyex]

I recently acquired 1 of these on ebay. However, mine acts slightly differently. It boots into Tiger and is usable for a few seconds before the CPU overtemp and checkstop LEDs (#2 and #7) come on and it locks up. What's interesting is I can long press the power button to shut it off and turn it on again with the same result. Changing the power setting to "reduced" gives a couple more seconds of usability before it overheats.

There are a few things I plan on doing in the spring.
1) Perform the "new blood" mod on my version 2 liquid cooler. This will be done outside due to the degrading toxic coolant in the loop. There should be other mods out there for version 1 coolers.
2) Repaste the chip on the back of the logic board (northbridge?) since that seems to be an issue with overheating if the plastic mounting clips melt and the heatsink comes off (or heatsink fins are clogged). This sounds like a possible design flaw. May also find a better way of mounting the heatsink and add an aid filter of some kind to the front.
3) Repaste whatever chip is under the large black heatsink on the front of the logic board.
4) Repaste the CPUs.
5) Do a deep clean of the whole system (incliding all heatsink fins and fans) while its in pieces.
6) Ditch the previous owners original hard disk with an SSD and a fresh OS install.

Until then I have the computer laying on its side on a table with the side panel off so if it does leak it won't (hopefully) get on the power supply.

May try documenting this on youtube. Don't think there are any videos like this yet and don't have experience with making videos.

Yeah, I have cleaned carefully almost entire my G5 (except the PSU bay). Have not put it back together yet

I will try to repaste it and see what will happen. I will post my result here

 

[giathyex]

Same issue after repaste. Guess I have to involved further with the LCS

 

[giathyex]

However, I notice that if I leave my G5 for a while to let it "cool down", I will got the boot chime, and after that the overtemp light kick on. But if I just turn it of and turn back on immediately, the overtemp light kick on right away

This make me believe my G5 just got an temperature issue and not too serious logic board problem. I will try to perform the "new blood" mod on my LCS

 

[mrbubzie1993]

Likely due to water system leak shorts to the power supply

 

[giathyex]

I have completely flushed the LCS. Now things get weird

After flushed and cleaned, the LCS works really well. Before I cleaned it, only the input port of the pump gets hot, the output port of the pump and the radiator doesn't get hot at all. Now the whole radiator gets hot nicely after my G5 turned on for a while

The overtemp light does not turn on any more. I got boot chime everytime I turn it on. Really make some progress here

But still get no display, nothing happen after the chime

Maybe I will try to find another graphics card. If the problem still not solved, next thing I may have to do is run it with only one CPU

 

[amishallin]

May sound like a stupid suggestion but did you try the GPU in a different slot?

Also, I like what you did there with the pump. Only replaced the 2 hoses? I was planning on taking the blocks that make contact with the CPUs apart also. If they are anything like modern waterblocks they should have little fins to transfer the heat to the liquid and may be full of crud. Figured I may as well cover as many things as possible.

The biggest thing that gets me about doing this is placing the LCS back into the machine. Was it as easy as lining up the screw holes and gently pressing down? The CPU pins like similar to my Quicksilver from the images i've seen.

 

[giathyex]

May sound like a stupid suggestion but did you try the GPU in a different slot?

Also, I like what you did there with the pump. Only replaced the 2 hoses? I was planning on taking the blocks that make contact with the CPUs apart also. If they are anything like modern waterblocks they should have little fins to transfer the heat to the liquid and may be full of crud. Figured I may as well cover as many things as possible.

The biggest thing that gets me about doing this is placing the LCS back into the machine. Was it as easy as lining up the screw holes and gently pressing down? The CPU pins like similar to my Quicksilver from the images i've seen

Yeah, I have tried different PCIE Slot. I even end up buy two another 6600LE (fair price) and still got the same problem. Boot up, got chimes, no display

For the LCS, I cut and remove these two hoses (with scissor, razor, cutting pliers), drain out old water, put vinegar + water 20/80 mixture in it, sealed and put the LCS in the sun for an hour

Then I run the LCS with the vinegar mixture using a DYI cable to get 12V power from standard ATX PSU

And then, I drain out the vinegar mixture, flush and run the pump again with clean water and distiled water. Finally, I put standard modern PC watercooler liquid in it and sealed back with two new hoses. You will want soft tubing (can buy from standard modern PC shop that sell custom watercooler) with inner diameter of 3/8" or 9.5-10mm

The hardest part in my opinion is to put new liquid in the LCS without letting air get inside it. I'm still kinda failed at that

And yes, I think the part of putting back the LCS same fairly straightforward as you mentioned. But you should be careful as I heard a guy on FB mentioned that he break something when he put them back (and I start to wonder if I have done something wrong and I dont even realize it, thats why my G5 is acting weird now and I kinda give up, looking for another working G5 )

This link may help you flush the LCS and make the cable to power LCS with standard PSU

 

[giathyex]

Powermac G5 Service Manual

This document maybe helpful

 

[amishallin]

Nice that service manual is newer then mine... mine was last updated on Jan 13 2006. More then likely just the addition of the extended repair program.

Also, that link to 68kmla looks like a great reference. However, I was thinking about using the G5 itself to power the pump while flushing it. Something like holding the pump in a tote with plastic tupperware full of clean solution and have it drain in the tote around the tupperware. Don't see why it wouldn't work and i'm sure the LEDs corresponding to CPU A/B fault will be lit... since they won't be installed.

Suppose another thing you can do is find a working G5 quad motherboard.

 

[giathyex]

I'm back, I find another G5 Quad in my country that looks like having a PSU problem (when I press the power button, the red light bright up then turn off immediately).

I take it home, swap the PSU from my G5 at home into it. After spending a few hours messing with all GPU I got, finally I found one GPU that work. I got it boot up and run perfectly fine.

Temperature fine (my room is at 35°C), run smoothly without any interuption.

Now I have a working Q5 Quad and a whole G5 Quad with a bad PSU laying around for parts.

 

[Eriamjh1138@DAN]

These PSs go on eBay and others for $50 to $150, shipped in the USA. I'm currently repairing a Lite-On version and hope to be done shortly after I figure out what parts I need. Mine appears to have gotten wet even though the CPUs show no sign of leaking.

Apple's had a PS recall back in 2006ish to replace supplies that simply died. Internally, there is a fuse, but it's there to protect against whatever is shorting out and killing these supplies.