27 inch iMac won't boot normally (screen flickers)

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27 inch iMac won't boot normally (screen flickers)

My old iMac (early 2009, 27 inch, 3.06 core 2 Duo, 4 GB 800 MHz DDR2 SDRAM) had, and continues to have a problem with the display. When attempting a normal boot, a minute or so after the Apple logo appears, the display goes black except for the top 10 or 20%, which rapidly flickers. I've run Disk Utility to verify the permissions and verify the disk and those appear okay. Also, ran the Apple Hardware Test from the install DVD and that appears okay, also. I've reinstalled Mountain Lion (a couple of times) hoping that maybe, somehow, it might surprise me but, still disappointed...

The easiest, least invasive thing I've done has been to just reseat the two memory sticks. Didn't hurt, but didn't help, either.

It's able to boot in Safe Mode, which I've been doing for quite a long while now, but it would be nice to have everything functioning normally again. Other than opening the iMac up to have a look inside, is there any other test(s) that can be done to get a better idea of what the problem might actually be?

Thanks.

iMac, OS X Mountain Lion (10.8.2)

Posted on Feb 3, 2013 8:18 PM

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Answer 1

rkaufmann87

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Feb 3, 2013 8:28 PM in response to jeff0987

Unless you ran AHT in Extended Mode at least 2-3 times back to back you really didn't run a comprehensive test. Even then AHT isn't the most reliable solution. Run AHT 2-4 times in Extended Mode back to back, if it doesn't show any errors take the machine in for professional diagnostics. Of course do this after doing both iMac SMC and PRAM resets and restarting in Safe Mode to clear some caches.

Good luck!

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Answer 2

jeff0987 Author

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Feb 3, 2013 8:45 PM in response to rkaufmann87

Thanks for the response.

I did the SMC and PRAM resets but still no luck.

I've done the AHT (short version) a few times in the past, but not (multiple) extended tests. Going to give that a try right now.

Thanks again.

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Answer 3

jeff0987 Author

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Feb 4, 2013 11:48 PM in response to rkaufmann87

Back again....

Well, gave the extended AHT 4 consecutive tries. Each time, it said that everything appeared okay.

So, guess I'll continue to get by with Safe Mode until I have the $$$ to get it diagnosed/repaired. Or, maybe some fine day, a whole new Mac. Something to look forward to :-)

Have a good one...

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Answer 4

rkaufmann87

Level 10

140,214 points

Feb 5, 2013 7:57 AM in response to jeff0987

The Safe Mode restart is very simple to do, when you hear the startup tone hold down the Shift Key until a progress bar appears. Let it fully boot then restart normally and test. If they problem continues then my guess is it's a hardware issue. If you still have AppleCare on it this should be covered.

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Answer 5

jeff0987 Author

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Feb 5, 2013 11:38 PM in response to rkaufmann87

It restarts okay and does what it's able to in Safe Mode. That's what I've been doing for a while, now.

Sure would be nice to have a fully functioning iMac again, though.

AppleCare is way in the past at this point. One of these days, I'll take it to an Apple Store and let them have a go at it. Or, at least give me the (bad) news as to how much it'll cost. 😮

If it should turn out to be the graphics unit (been reading less than complimentary things about Nvidia 8800 gs), any estimate on what Apple might charge for that sort of repair? If not, no worries. Guess I'll find out soon enough.

Thanks...

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