PowerMac G5 strange behavior when plugging an GPU

[RaikoBR]

Hey guys, I need some help with a PowerMac G5 (Early 2005 Dual 2.0Ghz). I recently bought one in working condition (no OS). I tested it upon purchase and it worked, but when I plugged it in at home, it chimed and tried to boot, but shortly after, it died completely.

Here is what I’ve found so far: The system chimes if I remove the 9600 XT. I bought a flashed FX 5500 to test, but it still doesn't work. I’ve also replaced the PRAM battery. At this point, I suspect the PSU is failing.

 

[AphoticD]

Hey guys, I need some help with a PowerMac G5 (Early 2005 Dual 2.0Ghz). I recently bought one in working condition (no OS). I tested it upon purchase and it worked, but when I plugged it in at home, it chimed and tried to boot, but shortly after, it died completely.

Here is what I’ve found so far: The system chimes if I remove the 9600 XT. I bought a flashed FX 5500 to test, but it still doesn't work. I’ve also replaced the PRAM battery. At this point, I suspect the PSU is failing.

Sadly, the symptoms do sound like a failing PSU.

I had two of my G5s fail recently. One is a Dual 2.0GHz 2003 model A1047, which had a power-hungry GeForce 6800 GT DDL and failed with a bang (and a cloud of smoke) after a short time of testing it recently. The 2nd unit (same series, but a 1.8GHz model with the low-power FX5200 GPU) seemed fine until it started to intermittently click off at random intervals, then quite reliably powering off after a few minutes of use. Now it can only stand upright for about 20 seconds before it clicks off. So I suspect the same degree of failure as the 2.0 unit, just not quite as dramatic. Both my units use the 600w (604w) AcBel PSUs.

Perhaps the 20+ year mark is just it for these power hungry towers. I am considering buying (one) replacement PSU to at least get the 2.0GHz model upright again, but these parts are quite rare (and expensive) now, especially where I live. So perhaps a technician component repair might be cheaper than replacement.

 

[Smithwick’s]

I wonder if there could be a twofold issue aside from the PSU. Perhaps it is actually the 9600 XT that has died, hence the failure in hardware detection prior to the chime. If you couple this with the FX 5500 it presents with a few possible failure points, because not all FX 5500s can actually work on mac even with flashing.

Is it an AGP version? Is it 3.3V? Do you know if the ROM was correct?

It could also be an issue with the AGP slot itself.

Hoping you can exhaust all other options before investigating the PSU, as that's a real pain.

 

[AphoticD]

It could also be an issue with the AGP slot itself.

This is a great point and something I had forgotten. My first ever A1047 was upgraded with a Radeon 9800 Special Mac Edition GPU that eventually started to show signs of VRAM failure, at which point, I packed the G5 away in it's original box and had it sitting in storage for about 5 years. Once I was eventually reunited with it, I tried powering it on and found it wouldn't boot – I can't recall the symptoms exactly, but it did receive power, fans would spin up, and the display would not initialize, but I can't remember if it chimed/POSTed.

I swapped out a number of components, including the GPU – I had the original FX5200 on hand, and got the same results. I had no way of testing the GPU to be known-good, so I bought another FX 5200 off the 'bay to test – and it still wouldn't boot. Eventually I realized that when there was no GPU installed, it would chime, I could hear the HDD grinding and the OS would boot up (headless). I eventually replaced the logic board on the basis that the AGP slot had failed and did confirm the 9800 was toast, but both FX 5200 GPUs were fine. So perhaps the higher-power draw of the 9800 caused my AGP slot failure in that case.

Long story short, it's worth having a shot at attempting to boot without a GPU and listen for the HDD startup sequence. If the HDD sounds like it eventually boots and stops grinding, try plugging in a keyboard with volume up/down to test for alert sounds or mash a few keys until you hear some beeps.

OP could then try a Mac PCI ATI Rage 128 GPU or similar (Like the Radeon 7500 or 9200) to prove an AGP fault.

 

[Certificate of Excellence]

OP could then try a Mac PCI ATI Rage 128 GPU or similar (Like the Radeon 7500 or 9200) to prove an AGP fault.

This was my thought. If Op has a PCI video card, that would point to AGP slot failure pretty quickly.

Not my auction. Found a cheap Apple 128 rage pro on ebay - $17.99 shipped.

 

[RaikoBR]

Hey guys, sorry for the late reply! Just an update: I’ve ordered a replacement PSU, which should arrive in a few weeks. In the meantime, I picked up a GeForce 6600 LE (unflashed).

Currently, testing with the FX 5500, the status LED stays solid white.

The current behavior is: fans spin up, but no chime, no video.

 

[RaikoBR]

I wonder if there could be a twofold issue aside from the PSU. Perhaps it is actually the 9600 XT that has died, hence the failure in hardware detection prior to the chime. If you couple this with the FX 5500 it presents with a few possible failure points, because not all FX 5500s can actually work on mac even with flashing.

Is it an AGP version? Is it 3.3V? Do you know if the ROM was correct?

It could also be an issue with the AGP slot itself.

Hoping you can exhaust all other options before investigating the PSU, as that's a real pain.

Yes, it’s an AGP Universal MSI FX5500-TD256. I’ve already cleaned the PCB with isopropyl alcohol, swapped the RAM sticks around, and repasted the CPUs. If swapping the PSU doesn't do the trick, I'll need an ESR meter to check the capacitors on the logic board.

 

[Certificate of Excellence]

Hey guys, sorry for the late reply! Just an update: I’ve ordered a replacement PSU, which should arrive in a few weeks. In the meantime, I picked up a GeForce 6600 LE (unflashed).

Currently, testing with the FX 5500, the status LED stays solid white.

The current behavior is: fans spin up, but no chime, no video.

Since you’re replacing the psu, take the extra 10 minutes to repaste the North bridge heat sink on the back of the logic board (you’ll have to take most everything out of the case to get at the psu anyways).

Good luck 🙂

 

[AphoticD]

Since you’re replacing the psu, take the extra 10 minutes to repaste the North bridge heat sink on the back of the logic board (you’ll have to take most everything out of the case to get at the psu anyways).

Good luck 🙂

Excellent advice. I'll be doing this for my "in-for-repairs" A1047 once the replacement 600w PSU arrives from the states – should only be another week or so.