PowerMac G5 boot problems.

Here’s the dealio: I have a powerMac G5 tower (7.3) with PCI-X, AGP, Dual 2.0Ghz & 4x 512MB ram cards occupying 4 of the 8 ram slots (they are occupying the ram slots in pairs.) I am dual-booting OSX 10.4.11 and 10.5.8 on a 160GB sata hard drive. I also have an IDE drive with OSX 10.4.11 that I have been using to troubleshoot, but is not currently installed.

Here is my problem:
(short version) The machine boots when it wants to, often requiring several hard power downs to boot.
(long detailed version) here are the steps to boot:
1. press pwr button, hear the click from the PSU.
2. Front fans briefly run full speed then immediately slow down to normal.
3. Next rear fans run full speed and immediately slow down to normal.
4. At this point in a successful boot, I would hear the apple startup sound, followed by audible hard disk activity (disk spinning, head movement), and finally the caps lock key will go through a series of turning on and off.
5. For an unsuccessful boot, the fans in the front will periodically speed up momentarily, then slow down – there is no discernable pattern. No apple boot sound, and no hard disk activity.
6. Occasionally, when the unit is rebooting from a software update, and I am not present, I will come back and all fans are running constantly at full speed.
7. If the unit hangs, I press and hold the pwr button until I hear the click from the PSU and the unit powers down, back to step 1.

When it boots, everything appears to work fine, and no indication of any issues whatsoever.

Here are additional troubleshooting steps I have performed:
• Removed optical drive, replace with IDE hard disk with tiger installed, disconnected sata hard disk.
• Removed all drives, and disconnected USB keyboard and mouse.
• Booted from optical drive only with tiger retail dvd.
All these attempts have resulted in the same symptoms.

Finally, here are tools at my disposal to do further troubleshooting:
• Powermac G5 7.3 tech manual.
• Powermac G4 tower.
• C2D macbook
• External ide hard drive enclosure with several ide hard drives.
• 4 & 8 GB flash drives (the flash and external hdds wont boot)
I don’t have any external firewire drives, or spare sata drives for testing; and I don’t have a firewire cable to boot any of my other machines into target disk mode.

The unit is new to me, so I don’t know its history. The previous owner is not helping, so there is a possibility it was problematic for him, and that is why he decided to sell it on craigslist. I plan on disassembling the entire unit this weekend and look for any distended capacitors or anything else out of the ordinary. I have never disassembled a Powermac G5, so I am apprehensive. I have disassembled G4s and g3s as well as limited disassembly of iBooks and g3 imacs.

Sorry for the very long post, but I wanted as much information out there so you all can help me troubleshoot this thing.

It sounds like you are right, unfortunately I can't afford any diags right now.

here is the latest:
After additional inspection, it looks as if one of the "nubs" the heat sink cover connects to is missing. I suspect it is still in the case somewhere. I don't have the proper hex screwdriver or a long bladed phillips to remove the CPUs, so it looks like this G5 is gonna occupy my shelf for the foreseeable future.

You are probably right. I don't expect him to respond to emails. The good news is I didn't pay cash for the unit, I traded a used DNS-323 NAS for it. New they are only $200, so I figure it was worth $150 or so. I only paid like $35 for it because it was non functioning, and "fixed" it. I guess the agp card might go into one of my G4 towers, and the optical drive is an upgrade to another machine; and the keyboard and mouse is in better condition than my set hooked up to my G4... Gotta find some kind of silver lining, right?

zen.state said:

This is why the informed do research on things before they buy.

Click to expand...

I sure hope this wasn't intended as a slight.


Anyway, here is the latest:
So I had written this thing off, as another victim of CL. I noticed the ram installed in this machine is high-density. It had sat over night with no power, so I pulled the ram, and found some low-density PC2100 sticks. of course the light on the front blinked twice to indicate no ram. I found some low-density pc3200, but was unsure of the voltage. put them in, and the unit immediately booted and gave me the apple start sound. I got the "restart your mac screen" so I did, once again it booted with apple sound. I wondered if the ram might have been the issue. I stuck in one set of the ram that came with the unit, and the previous symptoms occurred. swapped for the other set, same thing. put the other pc3200 ram in (that booted twice) and the symptoms persist. I suspect the ram may be causing some sort of issue. I am waiting until the power dissipates with the unit unplugged, to see if I can duplicate the results. Anyone know how long it will take? I don't want to wait over night again

The adventure continues while booting leopard or tiger install dvds:

I swapped the CPUs and I get the same error.