What is wrong with my G5?

[Project Alice]

Hi all,
I'm having a weird problem with my G5. It's a dual CPU 2.0Ghz early 2005 model.

A few weeks ago, after attempting to play a couple games, the screen started showing lines and weird colors all over. I assumed the GPU had failed. It was a Radeon 9800 Pro. At this point the computer was working fine other than graphic anomalies. I rebooted it a few times, and ran AHT. AHT of course failed on the GPU.
So, I stuck a GeForce FX 5200 in it from one of my other G5s. It booted to a black screen (after the grey apple). Started it up in safeboot and it worked fine. I figured something went wrong with the installation and just brushed that off.
Well, today I just got the new GeForce 6800 Ultra that I ordered. I installed it, plugged in the G5 and it does the same thing. Boots to a black screen. I have an external FW drive with both Tiger and Leopard that I use for starting up PPC macs. I tried booting it off of that, both Tiger and Leopard, and install DVDs from the external drive do the exact same thing, except after the grey apple it goes all *white* instead of black and is stuck there. I don't understand this, any ideas? Yes I've reset the PRAM ect, all the usual tactics.

 

[z970]

This is probably a useless comment, but have you tried vigorously rubbing the GPU pins with rubbing alcohol + microfiber cloth, as well as the slot on the logic board? This method has helped me out many times.

And are you absolutely sure those GPUs are compatible with your G5? I had the same behavior when I tried plugging in a known incompatible GPU in my G5 several days ago, so you can never be too sure.

 

[Project Alice]

This is probably a useless comment, but have you tried vigorously rubbing the GPU pins with rubbing alcohol + microfiber cloth, as well as the slot on the logic board?

And are you absolutely sure those GPUs are compatible with your G5? I had the same behavior when I tried plugging in a known incompatible GPU in my G5 several days ago, so you can never be too sure.

It's an official GPU for a G5, AGP Pro, and ADC slot. The 5200 that I put in there first came from another working G5 and was doing the same thing.

I have not however tried the rubbing alcohol thing. I suppose it couldn't hurt to try that.

 

[z970]

It's an official GPU for a G5, AGP Pro, and ADC slot. The 5200 that I put in there first came from another working G5 and was doing the same thing.

I realize that, it just seemed very odd to me that the two situations would exhibit the same result. Who knows, really.