I have been testing a 1.8 GHz G5 PowerMac.
I just had a few lock ups and then several failures to boot.
I tested a lot of things, but the only problem I can find is a faulty ground line on the power strip plug this was originally connected to (moved to another location).
Any ideas or similar problems?

edit - definitely not the ground.
Time to remove processors and test each separately.

[ Edited by Jim 01.05.2014 - 13:34 ]

First I will have to test the CPUs of this thing (which means getting a long #1 Phillips screwdriver to remove one at a time).
Hopefully I just have a CPU problem and not a problem with the motherboard or power supply.

Has anyone tried to swap faster processors (2.0 or 2.3 GHz units) into one of these?
I get mixed results doing web searches on this.

[ Edited by Jim 01.05.2014 - 18:21 ]

I'd hate to state the obvious, but have you ruled out defective RAM?

Quote:

No, the RAM was working in a G4, but that doesn't rule it out.
I'll check.

BTW - I will continue to investigate, but some 2.5 GHz machines appear to be upgradable to 2.7, and some 1.8 GHz machines to 2.0.

[ Edited by Jim 02.05.2014 - 12:52 ]

I had memory in my Pegasos 2 at one point that *appeared* to work OK at the 133MHz it was running at, but I had strange, weird crashes I couldn't explain. At some point I ended up in a situation where if I rebooted the machine, opened a shell, went directly to my source directory and compiled a specific file, the machine would hang. Any other action inbetween would stop it from hanging. I ended up testing the memory in a PC that could run it at 166MHz (which it was rated at), and at that speed, memtest86 found lots and lots of errors. Got the memory stick replaced, and the problem on my Pegasos 2 disappeared.

Whenever I encounter a machine that has weird, unexplainable and semi-random stability problems, the first thing I check is always the RAM. It is the most likely source of such problems in my experience.

Thanks Mark,
I have a few strips of PC3200 I can try.

Pulled the memory and found I had installed PC2700.
Replaced that with PC3200 and...now it doesn't post.
The power light flashes, and nothing else.
Bad memory socket solder joints?

Edit - I just installed four 512MB strips of ECC PC3200 that were formerly in my Sun Ultra 20 (which has been upgraded to 4GB of ECC PC3200 memory).

I wasn't sure ECC memory would work, but it works like a charm.

So far, it boots and is running stably.
Thanks Mark.

Now to dig out that MorphOS CD...

Second edit - nope, it started acting up again.

[ Edited by Jim 06.05.2014 - 18:07 ]

Definitely heat related.
Boots once cooled off.
Freezes later.

Any ideas?
CPUs or mainboard?
Solder issues?
Anything?

Quote:

Does the power light flash when this problem occurs (number of flashes can specify problem)?
https://discussions.apple.com/thread/2620983?start=0&tstart=0

Any diagnostic LEDs lit up (adjacent the the RAM sockets, near the front of the case; not present on some models)?
http://support.apple.com/kb/HT2652

There's also a couple of red LEDs on/near the processor boards which may be indicative of processor fault. (One of these was lit up on mine prior to me discovering the remains of coolant leakage).
https://discussions.apple.com/message/9196626

I feel like I'm pointing out the obvious, since you've been playing with the G5s longer than I have.

Is it air- or liquid-cooled?

Does it boot far enough to check any system monitoring tools (temperature sensors)?

[ Edited by boot_wb 07.05.2014 - 01:57 ]

Temperatures appear to remain good.
Power light only flashes after warm up and failure to boot, no code, steady flashing rate.
Lock up occurs are several minutes of use, once thoroughly warmed up.

Lockups appear at about 40C (CPUs), but the memory controller heatsink runs slightly warmer than the CPUs.
Could this be part of the problem?
Does anyone know where this is on the mainboard?

Edit - Mem controller currently at 50C and climbing, not locked yet.

[ Edited by Jim 07.05.2014 - 17:33 ]

Quote:

That seems to be the norm, in fact yours runs cool:
http://forums.macrumors.com/showthread.php?t=1155268

Quote:

The underside it would seem:
http://forums.macrumors.com/showthread.php?t=1155268

/Wolfmode

Yep, it never gets a chance to get too high, but it does consistently lock up once the memory controller hits about 52C.

Without a firm idea of the exact nature of the problem, l am shelving this system until I find a cheap parts machine.
Right now, there is a seller in NYC with 3 2.7 GHz G5s at $99 each.
In the US it makes sense to focus on 2.3 to 2.7 GHz machine, unless you get a really good deal on a slower machine.

[ Edited by Jim 07.05.2014 - 20:53 ]