Currently Being ModeratedSep 30, 2011 10:48 AM (in response to praetas)
Try booting up in safe mode. Safe mode will use a different video driver.
Try a safe boot.
Shutdown your machine. Hold down the shift key. Poweron. Wait awhile Wait awhile while you harddrive
is being checked.
My first guess would be a hardware problem. Run hardware diagnostics.
Currently Being ModeratedOct 3, 2011 12:54 PM (in response to rccharles)
Thanks Robert, so booting up in Safe Mode produced the same issues.
I did locate the Hardware Diagnostics disc that came with the computer, and it ran and detected a problem with the Video RAM. I got error: 2NVD/1/4:2103. I checked and this iMac has a Nvidia GeForceFX 5200 Ultra w/ 64MB RAM.
Would you guess from the error that the video card is bad and needs to be replaced?
Currently Being ModeratedOct 3, 2011 4:17 PM (in response to praetas)
I'd believe the hardware diagnostics.
I'd assume the video circiutry is integrated into the logic board. Could be expensive to replair.
Remember that Lion doesn't support old PPC programs in emulation mode.
Currently Being ModeratedOct 4, 2011 4:57 PM (in response to praetas)
I don't have an iMac G5. I do not know. I've heard that too.
You could try an Apple pi user group if you are looking for a friendly group to discuss the problem.
There may be an Apple Mac User Group in your area.
Currently Being ModeratedOct 9, 2011 7:15 AM (in response to Valerie Mcmillen)
No, not resolved yet. I have to examine the capacitors on the montherboard to see if any are bloated or have erupted. It sounds like its either that or the actual onboard video is bad, or both.
My client had the original discs that came with the iMac G5, and one of them was specifically a Hardware Diagnostics disc. That's how I was able to run the test. I dont know if you were trying from the disc or from within the OS...
I'll report on here once I get the problem identified, once its fixed and total cost.
Currently Being ModeratedSep 23, 2012 8:12 PM (in response to praetas)
I had a similar problem with our 2004 20" G5 iMac with the flickering screen of death followed by a kernel panic.
We are holding onto it because it still runs some legacy software that we use frequently.
We had recently upgraded and so our old iMac was moved to another room and placed on a cabinet slightly behind an obstacle that ran up to the level of the bottom of the monitor, and that's when the problems started.
I tried rebooting from a different partition, no joy.
I then read about problems of overheating of the graphics card due to poor ventilation and indeed, the lower right panel felt hot (I think that's where the GPU and VRAM live).
So the iMac was placed higher up with better ventilation and I ran Apple Hardware Test - AHT (extended suite) and as always, the fans run at full speed.
I got a VRAM error!
So I opened the iMac and cleaned out the 2 upper fans (they were filthy with dust) and restarted with good ventilation, fans a bit noisier as the crud blew out! AHT was run. No problem. Will have to clean the lower fan.
So in summary, an overheating poor ventilation problem.