24" imac freezing on gray startup screen

[bill19]

My early 2008 3.? GHz intel imac began having issues with a flickering screen (lower half) the other day when in p'shop. It would freeze and the power button was the only way to escape.

Restart was normal and all else was okay…but it also flickered once in Safari.. but that did not freeze the computer. It only flickered and only that once. And days went by with lots of usage but every time I launched P'shop (might take a few minutes but) it would freeze. (Downloaded GIMP for emergency graphic work)

A friend suggested and believed that the memory might be the cause. He said I should remove one of the two sticks and see if the problem continued. I removed ONE stick.. still had some p'shop issues and so I exchanged sticks… powered back up and saw no great improvement.

Then when I replaced both sticks and powered up it will not get beyond the gray window. The 'gear' symbol makes about 40 rotations then stops. Frozen again.

I tried all the PRAM and Safe Start up modes AND I have started in Single User mode several times. I get the --Modifications Were Made-- line and run /sbin/fsck -fy until it says it's okay. reboot and it stops on the gray screen. Over and over.

I tried starting up from my OS X 10.5.4 Disc but it too freezes on the gray screen.

Is my memory the problem? (haven't any to substitute)
Was it okay to try to start with only ONE stick?

Spent hours researching without answers.. and Any help will be appreciated!!!!!!

Thanks, Bill (a noob on the forum)

 

[chscag]

It sounds like your hard drive has gone south. See if you can start the machine in safe mode. Press and hold shift as soon as you hear the Bong sound. Safe mode does a disk verify during the boot cycle so if the disk is flakey, it should indicate it or fail to start. If it gets past that check, download the SMART Utility for Mac and run it.

 

[bill19]

Thanks chscsag,

Tried Safe mode first. No cigar.

Tried my cloned hard drive. Same symptom. (And I know the cloned drive is okay and has a good OS.) So I'm doubting a bad drive is the problem.

Don't have a Firewire cable or I'd put the imac in Target mode and try disc utility.... but I'm still thinking hardware problem. It worked, if a bit wonkie, before removing the memory, remember.

Anyone know if starting up with only ONE stick can cause hardware problems??

Thanks again! Bill

 

[techiesteve]

I've seen three 3.06 GHz 24" iMacs recently over a 2 week period freezing on the rotating cog as they boot. The DDR800 memory was OK, swapped to test. They wouldn't boot from an external drive, so pulled the hard drive, tried again, still wouldn't boot. Each one turned out to be the video card, only confirmed by substitution after isolating everything non essential from the logic board. There were no video glitches before freezing and Apples's MRI test (for AASP's and Genius Bars) passed everything, including the video, that wasn't helpful. This may not be your problem, but just an example of what can cause these symptoms if not the OS or hard drive.

 

[bill19]

Thank you, Steve.
With the flicker experienced and what I've read online it does seem to point to the graphic card. Can you direct me to instructions for replacement? Those on Youtube "How to Replace Imac 24 Video Card" show the "White" model whereas mine is Alum. Is the process similar? And where can I purchase the card?

Have other questions too, Steve. Could you contact me off forum? (bdavisstudio * yahoo.com) If that is permitted.

Any other suggestions from the forum are MOST welcome.. It's such a nice iMac and I'd like to get a couple more years service from it.

Thanks so much!
Bill

 

[techiesteve]

Bill, the only similarity between the white and aluminium iMac is that the video card is fixed to the rear of the logic board, everything else is different. Presuming you have this model, iFixit: The free repair manual show how to open up the iMac, but not how to remove the logic board to access the video card. That is held on it's rear by 3 screws and 1 temp sensor connector.

 

[shadey3000]

Having these same issues. Please let me know if you find any solutions to these problems

 

[bill19]

Shady3000,
Sorry, I've NOT found a solution. But believe Steve Bell (above) has pointed to the problem. It was/is not the OS and not the hard drive.

After more research, I've read on other forums that apparently the Nvidia 8800 GS cards used in the 2008 3.06 GHz 24" iMac have a high rate of failure. Most reporting theirs died after 3 years from new or shortly thereafter. (Mine, a used iMac with no previous problems, died into its 4th year.)

Some of those reporting also said the replacement 8800 GS cards failed very quickly (within minutes in a couple of cases) and some said even the third replacement card soon failed.

There have been class action lawsuits against Nvidia for shipping faulty cards but I do not think Apple was part of that (someone correct me if I'm wrong, please).

Consequently I removed the hard drive from my iMac and now at least have access to my work.

Thanks, Steve, for identifying the problem and please contact me if there's anything you can add.

Bill