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jamiesonjjeff Oct 16, 2012 04:27 PM
Persistent Sad Mac G5 iMac
I am very confused.

I have fixed many Macs and have never seen this issue, any help would be greatly appreciated.

I received a G5 iMac (no iSight) with no hard drive and an install DVD stuck in the Superdrive

I put in a known working hard drive and attempted to boot from the OS Install CD

The iMac did its impression of a jet engine for a while then I shut it off. Nothing happened.

Reseated RAM
Reset PMU

I had to take the Superdrive apart to remove the OS Install DVD and try a different one. This time the disk is not recognized.
I am using Single Layer DVD's since this Superdrive does not support DL.

Here is the really weird part

When I boot the computer in target disk mode both the OS DVD and the hard drive are recognized and accessible from the other computer.
I then proceeded to reformat the drive with Apple Partition Map and install the OS
The install completed successfully and I disconnected the firewire cable and rebooted the computer

Still get Sad Mac

It doesn't make any sense to me.

Please help
reader50 Oct 16, 2012 04:40 PM
It may have incompatible or bad RAM sticks. Those wouldn't matter to Target Disk Mode, but come into play when you try to boot. Does the power light blink, indicating a failed POST? If so, how many blinks in the cycle?
jamiesonjjeff Oct 16, 2012 05:03 PM
There is no beeping to indicate POST failure. I have tried booting with only one stick of RAM as well instead of the two it came with and have tried rotating slots. Forgot about that. Is there anything else that you could think of that may interfere on the iMac that does not come into play in TDM?
reader50 Oct 16, 2012 06:34 PM
The CPU. Let's not go there.

Substitute some known-good PC3200. Both sticks might be bad or the wrong type. In which case swapping or testing one at a time would not help.

Examine the motherboard and what you can see of the power supply. The pre-iSight G5s were hit by the Capacitor Plague. Look for bulged or leaking caps. Bad caps could impact things the moment it starts to draw real power.

edit: Got any peripherals connected? Besides the keyboard and mouse, you may want to disconnect anything else. Like the internal Airport card and/or internal bluetooth. I don't recall if they were on the same board.
Waragainstsleep Oct 17, 2012 01:49 AM
Can you boot it into Open Firmware? There are some resets you can do from there if so.
P Oct 17, 2012 03:11 AM
It could be that the PSU is giving up, and the low load required by target disk mode is just about all it can supply. When it's hard to diagnose, I always suspect the PSU on those models - capacitors from that era were notoriously finicky.
D R Turbo Oct 18, 2012 12:37 AM
You might want to try an SMU reset (not the same thing as a PMU reset). Apple started transitioning it's systems with a host of confusing names and procedures for resetting them around the time the non-iSight G5 iMac's were on the market. Most people think the SMU is an "Intel only" thing, but it isn't. If you haven't tried this, here's the procedure:

1. Unplug all cables from the computer, including the power cord.
2. Wait 10 seconds.
3. Plug in the power cord while simultaneously pressing and holding the power button on the back of the computer.
4. Let go of the power button.
5. Press the power button once more to start up your iMac G5.

The reason I say this is that you said it did it's "impression of a jet engine" which I assume means the fans were running. The SMU controls the following:

• provides initial configuration of system clocks
• automatically initiates and sequences voltage and frequency slews when the OS requests a transition to a new run level
• handles all power button and environmental user events
• controls RPM fans
• provides processor Mode Ring and thermal data store
• monitors processor temperature and power consumption
• monitors VRD10-compliant processor power supply digital interface.

(Both of those lists are from Apple, by the way, not me).

If you notice, a fair number of those items are thermal related, which to me is kind of a clue. Of course, if you've already done this, then I'm wasting your time.:\

Good luck.
Waragainstsleep Oct 18, 2012 12:43 AM
Actually the PMU applies to the G5 non iSight, the SMU to the G5 with iSight and the SMC to the Intel Macs. These resets are basically equivalent. One replaced the other which replaced the other.

I still think an OF reset is well worth a go.

Boot holding command, O and F and you should get a grey screen with a command prompt.



Press return after each of those two commands.
See if that helps.
D R Turbo Oct 18, 2012 02:42 AM
Check out this link:

Apple's terminology as well as how it's implemented over the years is, to say the least, confusing, and it varies from model to model, and possibly even from nation to nation for all I know.

To the best of my knowledge any of the resets anyone has listed can't hurt the system, particularly on one that isn't booting. I believe these types of Mac's also have a backup battery (like PCs) that retains some settings, but which I'm not sure of. Considering the age of the system, I wouldn't be surprised if it's dead. If the OP does a reset and it magically works, then fails after turning the system off, that might be a clue.

I wouldn't argue with anything anyone has posted so far.

Hope this helps.
jamiesonjjeff Oct 18, 2012 06:25 AM
Thanks for all the suggestions guys. I've tried so many things over the past week and a half that I can't hardly remember what I've done. I know I have done some of thee already but it never hurts to try again. I'll perform all of the suggested steps this afternoon to see if I can find a resolution. I'll let you know what happens. Thanks again
P Oct 18, 2012 07:07 AM
What do the indicator lights say when you try to start up?
jamiesonjjeff Oct 18, 2012 07:18 AM
The indicator lights tell me that everything is working fine. 1, 2 and 3 are green
jamiesonjjeff Oct 18, 2012 12:34 PM
I performed the open firmware resets again and rechecked all the capacitors. There does not appear to be any issues with the capacitors. I also tried the suggestion from D R Turbo.
I'm going to get another stick of RAM tomorrow and see if that is the issue
jamiesonjjeff Oct 19, 2012 05:16 PM
Well i tried some new RAM and that didn't fix it, but thanks to P, I took a look inside the PSU and found a few larger than life capacitors. I really hope thats the only problem. I'll update again when/if I get the PSU replaced. Thanks again all.
Patrick Dec 12, 2012 11:46 AM
Quote, Originally Posted by Waragainstsleep (Post 4196792)
Actually the PMU applies to the G5 non iSight, the SMU to the G5 with iSight and the SMC to the Intel Macs. These resets are basically equivalent. One replaced the other which replaced the other.
I still think an OF reset is well worth a go.
Boot holding command, O and F and you should get a grey screen with a command prompt.
Press return after each of those two commands.
See if that helps.
Probably unrelated to jamiesonjjeff's issue, but I had a seemingly dead iMac G5, which was giving me errors when the Apple Hardware Test got to the VRAM, and this trick actually fixed it. There was one extra step in the solution I had found, though. From the Open Firmware screen, I typed the following:


Does the second line make a difference? I know pretty much nothing about Open Firmware or NVRAM, and had come across the solution unexpectedly while using another computer to search for information about the logic board. Thought I'd have to spend some cash for either a spare logic board, video card, or a new computer, so I'm thrilled.

EDIT: I'd turned it off earlier, turned it on again, and got the same problem - I guess that wasn't a fix after all. Might be a loose connection or something not seated properly; I gave the monitor a bit of a shake, and it somehow fixed itself. I guess I don't have magic firmware after all.

EDIT #2: after reading through the threads here, it looks more like a hardware issue involving the GPU. It may have overheated one too many times. In the past, I've inadvertently blocked the air intake a few times, plus there was that hard drive that overheated a few years ago. Also, earlier this evening I took out the logic board and found that the heat sink was so full of dust and lint (8 years' worth) that there wouldn't have been much airflow. Oh well… clean out your iMacs, folks.
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