PowerMac G5 - Not Starting

[mddguy]

I recently acquired a PowerMac G5 (Dual Core 2.0GHZ late 05) in perfect/as new condition, including the original box. It is an Apple Certified Reconditioned Model, shipped in March 2006.

Unfortunately though, it doesn't turn on. If I try to turn it on, I just get two click sounds, and the front panel LED illuminates as the button is pushed. The fans don't move.

If I take the air deflector out, the Trickle Power Light comes on inside, and it is supplying power through the FireWire ports, as I charged my iPod with it.

Here's what I've tried so far
- Reset the PMU (the little button inside)
- Removed the Battery and unplugged the system for approx 10 minutes to clear settings etc (I haven't replaced or tested the battery)
- Reseated RAM and GPU
- Reseated all fan connections
- Reseated the two cables from the Power Supply (not the large studs)

I'm thinking next I should reseat the CPU, subject to finding the correct tools. If that doesn't work, I guess I'll have to buy a new Power Supply, assuming that is actually the problem.

Does anyone have any suggestions for other things I could possibly try or check.

 

[AphoticD]

I would try reseating the CPU module as you’ve pointed out. It sounds like the power supply is working okay.

If that doesn’t solve it, then perhaps the CPU overheated and failed at some prior stage, so you could try replacing it. Your model will take a Dual Core 2.0ghz or 2.3ghz module. It’s also possible the RAM is no good, so try sourcing a pair of known working DDR2 (533mhz) modules.

For the CPU removal tool, I took the cheap option and just modified an existing hex key to come in from the side / front of the CPU instead of reaching down from the top with a long tool.



It’s a low profile space to get in, so one end of the key had to be made short. This one was first bent straight and then turned in at about 8mm from the inside edge. You could use a vice or a pair of multigrips or pliers. The key diameter is about 4mm.

This tool is only specific to the late ‘05 Dual Core models and not suited to any other G5, which do require a long (smaller diameter) tool.
[doublepost=1523581773][/doublepost]Another thought; I’ve had the same kind of non-boot issue with a failed GPU on an earlier G5. You can try removing the graphics card and then power on. If you get a chime then replace the GPU.

 

[mddguy]

Thanks - I've tried running it without the GPU and the Memory - at least if it powered up and beeped at me I'd know it was one of those.

Handy trick with the allen key. I found a 4mm tool on Amazon with a long shaft cheaply, but that is good to know.

I never thought about putting a 2.3 in, but that’s a great idea.

 

[MagicBoy]

Sounds similar to mine. It was a faulty PSU.

 

[mddguy]

I would try reseating the CPU module as you’ve pointed out. It sounds like the power supply is working okay.

If that doesn’t solve it, then perhaps the CPU overheated and failed at some prior stage, so you could try replacing it. Your model will take a Dual Core 2.0ghz or 2.3ghz module. It’s also possible the RAM is no good, so try sourcing a pair of known working DDR2 (533mhz) modules.

For the CPU removal tool, I took the cheap option and just modified an existing hex key to come in from the side / front of the CPU instead of reaching down from the top with a long tool.

View attachment 758084

It’s a low profile space to get in, so one end of the key had to be made short. This one was first bent straight and then turned in at about 8mm from the inside edge. You could use a vice or a pair of multigrips or pliers. The key diameter is about 4mm.

This tool is only specific to the late ‘05 Dual Core models and not suited to any other G5, which do require a long (smaller diameter) tool.
[doublepost=1523581773][/doublepost]Another thought; I’ve had the same kind of non-boot issue with a failed GPU on an earlier G5. You can try removing the graphics card and then power on. If you get a chime then replace the GPU.

Well, I tried reseating the CPU, and that didn’t seem to do anything. Although I did connect the power while it was out and it did shine the red CPU light.

I took out the PSU cover and interestingly it has the 1000w PSU found in the Quad.

Now I need to figure out if I’m buying a new CPU or a new PSU

 

[mddguy]

Sounds similar to mine. It was a faulty PSU.

I'm starting to think that is the case. Did yours also still put power out of the Firewire ports and light up the Trickle LED?

 

[AphoticD]

I'm starting to think that is the case. Did yours also still put power out of the Firewire ports and light up the Trickle LED?

If you have a multimeter, you can compare the PSU voltage output with the pinouts listed in the Apple service manual for the late ‘05 G5;
http://tim.id.au/laptops/apple/powermac/powermac_g5_late2005.pdf

This would determine if it is indeed the PSU or something else. Something else being either likely the CPU or logic board.

The 1000w PSU is correct for this model. It won’t ever need to draw that much power though.

 

[Sydde]

There is some sort of power manager called “CUDA” that has a reset button. Try that first.

link

 

[MagicBoy]

I'm starting to think that is the case. Did yours also still put power out of the Firewire ports and light up the Trickle LED?

Trickle LED - yep.
Firewire port - dunno.

 

[AphoticD]

On page 6 of the Apple service manual I linked to earlier, it describes a recall on the 1kw AcBel power supply used in the late ‘05 G5. Apparently they had known component failure with these PSUs and extended the recall two years past the original purchase date only.

The affected serial ranges are:

• CK539xxxxxx – CK608xxxxxx
• G8539xxxxxx – G8608xxxxxx
• YM539xxxxxx – YM608xxxxxx
• RM539xxxxxx – RM608xxxxxx

It states that a 710w (non-AcBel) PSU can be used in place of the 1kw unit when installed in the dual core 2.0 or 2.3 models.

I can’t recall if my Dual Core had an AcBel branded PSU, but it is 1kw and does fall within the SN range, so it must. I guess if it hasn’t failed after 12 years due to defective manufacturing then it’s unlikely to do so until the components give out due to age.

 

[mddguy]

On page 6 of the Apple service manual I linked to earlier, it describes a recall on the 1kw AcBel power supply used in the late ‘05 G5. Apparently they had known component failure with these PSUs and extended the recall two years past the original purchase date only.

The affected serial ranges are:

• CK539xxxxxx – CK608xxxxxx
• G8539xxxxxx – G8608xxxxxx
• YM539xxxxxx – YM608xxxxxx
• RM539xxxxxx – RM608xxxxxx

It states that a 710w (non-AcBel) PSU can be used in place of the 1kw unit when installed in the dual core 2.0 or 2.3 models.

I can’t recall if my Dual Core had an AcBel branded PSU, but it is 1kw and does fall within the SN range, so it must. I guess if it hasn’t failed after 12 years due to defective manufacturing then it’s unlikely to do so until the components give out due to age.

This must be why I thought the 1000w was a replacement, 710w sounds a lot more suitable for a Dual Core. Mine does not fall within the serial range.

 

[AphoticD]

This troubleshooting process (page 145) seems to describe the issue you're having. Are you able to try the highlighted resistance test? These are the terminals on the back end of the processor module which have the black and grey leads running to them from the PSU.

The short you're testing for must have been typical enough for Apple to list the ohm test as a startup symptom step. Normally it would just state something like "Install a known working power supply".

 

[mddguy]

This troubleshooting process (page 145) seems to describe the issue you're having. Are you able to try the highlighted resistance test? These are the terminals on the back end of the processor module which have the black and grey leads running to them from the PSU.

The short you're testing for must have been typical enough for Apple to list the ohm test as a startup symptom step. Normally it would just state something like "Install a known working power supply".

View attachment 758575

So a quick update. I replaced the PSU with a 710W PSU and it fired right up!

The only thing that seems to be a problem is the PCI Fan intake is running at around 1500rpm when idling so the G5 sounds a little like a idle MDD!

 

[AphoticD]

So a quick update. I replaced the PSU with a 710W PSU and it fired right up!

The only thing that seems to be a problem is the PCI Fan intake is running at around 1500rpm when idling so the G5 sounds a little like a idle MDD!

Great to hear you've got it back up and running!

I would try using the Apple Service Diagnostic (ASD) v2.6.3 disc to run through the calibration process. That should resolve the constant fan noise.

ASD is now up on the archive at: https://archive.org/details/asd.2.6.3 - Download the "Mac OS X Disk Image" link and burn with Disk Utility. You can then hold the C key while booting to drop into ASD for OF. Let it run through a full hardware test and then try to calibrate the CPUs from the menu bar.