PowerMac Dual 1.8 PCI Sudden Shutdowns

[sxl1681]

I've brought my old PowerMac G5 dual 1.8 PCI model (OS X Leopard) out of retirement to pull some data from DV tapes now that I have time and storage to store the raw data. The problem is as follows.

First day, it powered on. It didn't boot up right away but a reboot had it up and running. Obvious PRAM battery dead when the incorrect date and time were shown. Simple fix and I had one spare battery left with charge. I cleaned up a bunch of crap to make space and installed a Seagate NS1 750 GB drive into the second HD slot and formatted. No issues noted so far. The computer continued to run for about 4 hours straight without issue as I ran software installs for the project. I powered the computer back off for a few days while I wait for a Canon XL-1 power adaptor to arrive to replace my dead one.

A few days later, I got the power adaptor and fired up the computer again. No issues noted initially and the computer ran fine and captured video from the camera for about 45 minutes when it just suddenly shut down. I thought initially the power saving mode kicked in but when I rebooted, it chimed but the screen never came out of its power save mode before the G5 shut down again.

Ok, so now I'm thinking power supply and power cord. I test and did find that the power cord was sitting a bit looser in the socket than I like so I replace it with a more snug fit model.

This time the G5 boots, screen turns on, gets about halfway through the boot process and then shuts down.

I hit the power button right after, it turns on, chimes and turns back off after about 5-10 seconds, before the screen kicks out of power save.

I then shut off the computer and opened it up, reseated the video card, removed an ATTO SCSI card, and had a good look around for dust and debris. The computer was off for about 15 minutes.

I then powered it on. I did a PRAM reset just in case. The computer ran for about 10 minutes before it shut down again. This was enough time for me to verify that power save mode was disabled and I was able to remove the ATTO kext in case that was causing issues. During this boot, I verified that every fan was operational.

I hit the power button again right after shutdown and again it boots up for 5-10 seconds and then shuts down.

So my thinking is this, probable thermal issue? Would this be some others conclusion? I don't have a tool yet to verify that the CPU paste is still good. I should have it by next week. Is this the likely issue? Of note is that when I touch the CPU heatsinks after shutdown, they are warm but not hot, not hot like I used to remember them getting. This also is leading me to suspect thermal paste is the issue.

One thing against the CPU overheating however is that the CPU fans do not spin up like they should if the CPU was hot. The CPU fans do throttle up and down as I heard them doing that during the DV capture.

I don't think it is a power supply issue as it will boot up every time I press the power button without issue but I cannot rule this out yet that maybe there are some caps failing and putting noise on the rails.

I also booted from the Leopard DVD and it also shuts down about 20-30 seconds into the boot process.

Asking for advice on where the problem may lie. I don't want to chase around tearing the cpu's from the motherboard if it is not needed since the socket is easily damaged. The CPU fans not spinning up to full blast is making me suspicious that it may not be the CPU paste after all unless the temperature sensor is on the heatsink and not in the CPU itself.

 

[1042686]

Hmm, if you could get to terminal, you could see what the OS says is the reason.

1st thing I’d do is DL the manual & follow the trouble shooting section - maybe check the psu voltages etc. & move forward from there.

http://tim.id.au/laptops/apple/powermac/powermac_g5.pdf

Either way on a 15+ year old computer it is a good idea to clean & repaste the CPU.

 

[sxl1681]

As a followup, it turns out it was the power supply going bad. I tried new thermal compound on the CPU and heatsink with no change. The CPU grease was starting to dry out but it was technically ok yet. I found a cheap power supply on eBay to swap out and this cured the problem.

Funny how my dual 1.8 GHz G5 has now gone through 2 bad power supplies and my brother's dual 2.5 GHz still chugs along just fine on the original. Both probably have close to same power-on-hours.

I opened up the bad power supply afterwards and didn't note any bulging caps or anything out of the ordinary. Guess it is some caps drying out or other devices slowly dying. Not sure if it is worth trying to fix as long as cheap power supplies are available on eBay. If someone want's two bad ones to repair, I'll mail them out, just cover postage.

 

[1042686]

As a followup, it turns out it was the power supply going bad. I tried new thermal compound on the CPU and heatsink with no change. The CPU grease was starting to dry out but it was technically ok yet. I found a cheap power supply on eBay to swap out and this cured the problem.

Funny how my dual 1.8 GHz G5 has now gone through 2 bad power supplies and my brother's dual 2.5 GHz still chugs along just fine on the original. Both probably have close to same power-on-hours.

I opened up the bad power supply afterwards and didn't note any bulging caps or anything out of the ordinary. Guess it is some caps drying out or other devices slowly dying. Not sure if it is worth trying to fix as long as cheap power supplies are available on eBay. If someone want's two bad ones to repair, I'll mail them out, just cover postage.

Out of habit, I always scavenge the fans as they’re a handy size to have around & send the rest to recycling.

 

[z970]

Out of habit, I always scavenge the fans as they’re a handy size to have around & send the rest to recycling.

I tend to keep those and all the wiring as spares. It's also good to extract out some of the (sometimes copper) heatsinks in these supplies. You never know when they might be of use...