Power Mac G5 Repair

The PowerMac G5 is a desktop computer first produced in 2003 by the Apple Corporation. This guide will review the repair process of an Apple PowerMac G5 model number A1047 EMC 2061 from 2004. It was discontinued in 2006 as part of the Intel switch first to developers then consumers.

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Reluctant to Boot (first, chime), Freezes or gives Kernel Panic in OS.

Hi Folks,

I've found some great questions and comments on iFixit, and commented there myself, but was recommended by Mayer to start up a new Question. So, here goes:

My PowerMac G5 (June 2004) is very reluctant to boot. My situation is very similar to that of others who have posted (with no resolution). Most of the time I'll get no chime, and will only hear the optical drive revving up, will not get video, and all this will be followed a few minutes later by fans which get increasingly louder, forcing me to shut it down manually.

Thanks to some posts, I tried resetting the PMU/SMU by the button on the bottom of the Logic Board. That worked to allow the computer to boot, and I heard the lovely chime and finally got power to the screen. I thought I was home free. The next day however, the computer froze with a Kernel panic that read as follows:

System Failure: cpu=1; code=00000001 (Corrupt Stack)

Latest crash info for cpu 1:

Exception state (sv=0x6bc1ea00)

I checked out some forums that had similar errors (though none exactly the same beyond the first line) and when I was able to boot the next time and get into the OS, I checked the system profile and noticed that it said I had 2 processors (which I do).

I read some other forum threads that said one should check the Console to look for consistent errors. I noticed one of this basic nature occurring a lot:

com/apple.SystemStarter[X] The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec().

Break on __ THE_PROCESS_HAS_FORKED... to debug.

''[the ... is mine, indicating that it's the same message as prior]

[X = several different numbers]''

I also notice this message

... *** error for object 0xa1b1c1d3: Non-aligned pointer being freed.

  • set a breakpoint in malloc_error_break to debug

[... = osascript(289), and other things in other instances, or perhaps it was just the number that changed]

I was able to get to the console because it started to boot and even restart successfully. However, the Apple Hardware Test procedure didn't go so well.

I was unable to use a USB keyboard to enter commands during boot, but was able to use the Apple BlueTooth one. I was only able to get it to recognize the holding down of "Alt" during startup, though, which allowed me to boot to the AHT DVD. I started performing the Extended Test and the G5 froze after 50 seconds and the fans remained blowing very loudly.

I had devised a method which seemed like it was working to make the G5 start:

1) Unplug power

2) Reset PMU

3) Plug cable back in while holding power button

4) Release and then press power button

Alas, this process didn't work after two times, so I don't think it was the process itself that was doing it. Perhaps it's the amount of time between attempted starts.

Oh, and BTW, I tried removing and switching out RAM. No go.

I'm not sure if I'll be able to use it, but if you could direct me to the Apple Service Diagnostic, that'd be great.

Thanks Mayer, and thanks All,

Andrew

Answered! View the answer I have this problem too

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+ excellently stated question. I have some ideas but need to get into my Apple Service manual and refresh myself to avoid giving you any red herrings. What is your current RAM configuration?

by mayer

My current config is 1 GB of Ram. I had 5 total (2-1 Gigs, and 6-512 MB) when the unit failed, took out the 2-1 Gig chips to put in another computer, and have tried booting with just one pair in at a time, trying different pairs. No luck. I think it's probably not a RAM problem, given the lack of chime. From what I've read, similar non-boot problems seem to go away temporarily when the G5 has been left unpowered for a period of time. I just got home and tried to boot and got a Gray screen with an Apple. I couldn't get any video before I left. 30 minutes+ did something, even though I did have it plugged in during that period of time.

by Andrew

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Hey Andrew have you tried your computer with the disk that came with it? The reason I ask is because the Majority of times I get the error you are having on my clients computers I reinstall the system and that usually fixes the problem. I have also seen them fix themselves after running Apples Disk Utility.

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I was able to use the Apple Hardware Test that comes on the DVD bundled with the computer. It passed both Quick and Extended tests. I was not able to run Disk Utility because I didn't go to the OS. I wanted to see if I could have it boot to the ASD disc. I made it wrong, so that didn't work. I made another, correctly, but now it won't boot to the point of providing keyboard input or monitor output again. I imagine the problems that would be resolved by using Disk Utility are just the icing on the cake.

by Andrew

Have you tried putting in a new hard drive and try loading a new system on it?

by mactech plus

I have not. I don't have an extra hard drive to try, and the hard drive in there is one I purchased only late last year. Do you really think it would be an issue with the hard drive even if I'm not getting chiming or keyboard input? As far as I know the basic booting should be working with the Logic Board (i.e. Open Firmware), and not the hard drive, or else I wouldn't have the option to choose to boot to the HD or the DVD (if I can get it to boot at all).

by Andrew

I pulled the HD from the G5 and am checking it with Disk Utility on my wife's MB Pro using my USB to SATA connector. It says there are some issues and I'm repairing them now. While I doubt that this could be the problem, I thought it was worthy to at least evaluate the possibility. Thanks for your help, MacTech Plus. These are the issues Disk Utility says there are with the HD: Invalid volume file count (It should be 883930 instead of 883931). Invalid volume directory count (It should be 212571 instead of 212570). The volume Mac OS X was found corrupt and needs to be repaired. Error: This disk needs to be repaired. Click Repair Disk. I repaired and it looks like the issue is resolved. I'll now try to put the HD back in the G5 and boot.

by Andrew

Ok, no boot. Do you still think it's the HD? Should I try formatting and installing OS X on the HD while connected to my USB-SATA adaptor? I have all the data backed up through Time Machine on my external HD.

by Andrew

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First take out all the added RAM. Use only the original and make sure they're in the proper paired slots. This diagnostic will most likely take some time and may be a matter of elimination.

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I don't know if I have any of the original RAM. I'll try another set. I've tried two different sets, thus far, each properly paired in the 1 slots.

by Andrew

The ADH failure is good in a way. It tells us that the machine has a hardware problem.

by mayer

Tried all pairs of RAM. With the last pair I got to a gray Apple screen with no activity. Forced shut down and retried booting, this time with no chime or video. I've had just as much success with all pairs of RAM, and was able to fully boot with the pair prior to this one. The problem seems to be inconsistent even within tests of a single set of RAM. I suspect the problem lies with one of the big 3: Logic Board, Power Supply, or Processor(s). As mentioned earlier, I've checked System Profile, and it shows 2 processors (there's precedent that it should show only 1 if only 1 is functioning), which potentially rules out the processors. Given the fact that it is more likely that the unit will chime and provide video the longer it's sat unpowered, I'm inclined to say the culprit is the PSU, however, I suppose it could be the MOBO as well. What are your thoughts?

by Andrew

My thought is a overheating component on a processor or the logic board. But I suspect one of the processors. Set the RAM to the pair that gave you a full boot. I take it you have another machine that you're writing with, what is it? If a Mac download this and burn to a DVD: http://flmsdown.net/software/634367-appl...

by mayer

Hmm. I'll try that pair again. I'm writing on my wife's 13" Unibody MacBook Pro.... Nope that didn't work. No chime, no video. Just a spinning optical drive and fans.

by Andrew

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I can suggest if you are willing to lift the procs up and re-grease

(not arctic silver) after that tun your 258 ASD but go to

calibration at the top and recalibrate the procs. if this does not work

you more than likely have a bad processor CPU 1 which would be the second one.

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What's wrong with Arctic Silver?

by mayer

I've purchased some Dynex thermal compound from BestBuy (under $10) and a 1/2AA 3.6V battery from RadioShack ($20). I really don't want to try the battery unless I have to, given that I'd like to be able to return it. I'll try the PRAM reset, which might work given how long the unit's been unplugged. I've downloaded the ASD and will burn to disc as well.

by Andrew

Wow… It was of the Tadiran brand, of which one of the posters said batteries are often dead at purchase. Definitely returning that one. And with a 3.63 V reading on the voltmeter, I think I can rule the battery out enough to at least wait in the mail a few days for a decently priced one.

by Andrew

I've removed the processor/cooling assembly, but I have no idea how to disassemble this without spilling coolant everywhere. The unit seems quite well tied together, and there are no guides here beyond simple removal from the case.

by Andrew

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Andrew will be eternally grateful.

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