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G5 Quad random shutdowns, what log to look at?

B

burnout8488

macrumors 6502a
Original poster
May 8, 2011
578
95
Endwell, NY
I'm experiencing random shutdowns on my 2.5 Quad. Temperatures are all perfectly fine.

One shutdown happened simply browsing the web, another was under high load encoding video to my PS3 (PS3 Media Server). It's done it about 4 times now. The last one, the computer acted as if it was going into sleep mode, but wouldn't snap out of it. (Power LED lit, black screen, non responsive)

I checked /var/logs/system.log and found nothing abnormal at all. When the computer shuts down, it doesn't log ANYTHING in there.

Is that the correct log to be looking at? Also, if the computer isn't logging a reason for the shutdown, does that hint towards what the problem actually is?

I'm considering replacing the CR2032 battery on the motherboard, if that sounds like it's a good idea. I haven't sold my old 2.0DP yet, which was reliable as dirt, and I don't know if I should. Maybe it's time to ditch the Quad before it gets worse? I love it to death because of its speed, but if its not going to be reliable, we can't stay together. :(
 
burnout8488 said:
I checked /var/logs/system.log and found nothing abnormal at all. When the computer shuts down, it doesn't log ANYTHING in there.

Is that the correct log to be looking at? Also, if the computer isn't logging a reason for the shutdown, does that hint towards what the problem actually is?

I'm considering replacing the CR2032 battery on the motherboard, if that sounds like it's a good idea.
Click to expand...

Yes, this is correct log. You can access it through the Console (it's more comfortable than Text Edit to search info inside logs IMHO).

Battery is quite good idea for the start, but symptoms you've described may indicate the beginning of PSU dying.

Check this out:

Power Mac G5 Repair Extension Program for Power Supply Issues

Power Mac G5 The Power Mac G5 Repair Extension Program for Power Supply Issues applies to Power Mac G5 systems that have power-related issues as a result of a specific component failure within the computer's power supply. If your Power Mac G5 fails to start up after the power button has been pressed and your computer's serial number is within the noted ranges, your computer may be eligible for repair, free of charge. There are no known safety issues caused by this component failure.

Identifying Affected Power Mac G5 systems
The affected Power Mac G5 models were sold between approximately October 2005 and August 2006 and feature Dual 2GHz, Dual 2.3GHz or Quad 2.5GHz PowerPC G5 processors.

If Apple or an Apple Authorized Service Provider (AASP) determines that your Power Mac G5 computer is eligible as part of the program, the power supply repair will be covered by Apple for up to two years from the original date of purchase even if your Power Mac G5 is out of warranty. This worldwide Apple program does not extend the standard warranty coverage of the Power Mac G5.

Affected systems will exhibit one of the following power-related symptoms:

* System will not start up after the power button is pressed
* No LED activity

Serial Number Ranges

CK539xxxxxx - CK608xxxxxx
G8539xxxxxx - G8608xxxxxx
YM539xxxxxx - YM608xxxxxx
RM539xxxxxx - RM608xxxxxx
Click to expand...

Program has ended OFC, but I've quoted it just for reference.
 
Thank you for the post! My box *does* fall in the serial range for the affected models, but I'm willing to bet pretty much every Quad does.

I've backed up my files to an external HD just now, and will reinstall Leopard to see if the problem returns, as well as the battery in a day or two. (Just to isolate the problem)

Just ran Apple Hardware Test, and it passed. The CPU setting has been on "Reduced" for a week now as well, still shutting down.

Really hoping it's not PSU now, even though all signs are leading to it.
 
So check the log. Try to remember exact time when next shutdown will occur. Look for any unusual errors in log near this time. But if it's PSU problem, there may be nothing logged because of sudden power loss.
 
I've checked the log and there have been zero errors before shutdown time. In some cases, there aren't ANY events within a few minutes of the shutdown.

Recently I reapplied thermal grease to my CPUs. I did not re run the thermal calibration after this, because I did not replace the CPUs. Is this necessary after removing them, even if they are the same?

Replaced the PRAM battery, still shuts down. The system will reliably turn off during a low level format it seems, so I use that as the test now.

Thank god I have this iPad.
 
Somehow I forgot this big detail.

When I got the computer, the graphics went garbled and eventually the screen turned off after about 1 minute of YouTube viewing. I could not get the computer to produce graphics after this, or produce a boot chime. I baked the 6600 in the oven for 8 minutes, and upon reinstalling it, everything worked fine again.

Can a blown video card really shut down my computer? Maybe this is the problem all along, I can't believe I forgot about that.
 
To rule out the card, remove it and access your Mac via SSH/VNC. PCIe G5 can run headless. Run some tasks like encoding or something and see if shutdown will occur.
 
Good idea! I might try that later.

So far, I've reseated the video card and plugged the computer into a power strip - it was plugged directly into the wall before. It's been running for over 12 hours now. Next time it shuts down, I'll assume it's the video card.
 
80% of failed PSU I've replaced in people's Macs were plugged like this (I was always asking them). Power strip with filter and fuse can significantly reduce the risk of PSU damage from instability of electrics source and extend PSU lifespan. It works, at least for me ;)

What I've noticed: laptop PSUs are more "immune" to this. They must have better protection built-in than desktop ones.
 
This must be one of the most sensitive computers I've ever owned, but I can see why. Still no shutdowns yet since putting her on a power strip (only fused I think though) and reseating the video card. However I wish I only did one at a time, to isolate the problem.

Thanks for all your help so far! :)
 
I have been working in a powersupply mfg company previously, this is what we call back then as brown out and surge protection. Your powersupply would shutdown once it senses a surge and a sudden drop in voltage it will not take more than a second for the circuit to detect. Its a circuit protection, nothing to worry about. Although most of the "modern" power supplies have in line filters in them, it is better to be more secure to place behind a filter and surge protector with fuse.
 
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