I have a 27.5 iMac where the screen locks up and has black and white vertical lines then automaticaly restarts after about 1 min. Some times you can turn on the iMac and there are no issues at all so it's an intermitent issue vs a hard failure.

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Brian7299 Author

Level 1

4 points

I have a 27.5 iMac where the screen locks up and has black and white vertical lines then automaticaly restarts after about 1 min. Some times you can turn on the iMac and there are no issues at all so it's an intermitent issue vs a hard failure.

Posted on Aug 20, 2017 12:24 PM

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Answer 1

Brian7299 Author

Level 1

4 points

Sep 2, 2017 5:18 AM in response to babowa

I repaired the graphics card by baking it in the oven and its working now but I know this will only be a temporary fix

Do you know if the graphics card in my iMac is used when an external monitor is hooked up and the iMac display is off? Or is the graphics card used regardless if you use an external display?

I was thinking if the iMac graphics card is not used with an external monitor that I might could buy some time by using an external monitor which would also be cheaper than a $500 graphics card.

Thoughts?

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Answer 2

SeaPapp

Level 7

26,492 points

Sep 2, 2017 1:14 PM in response to Brian7299

Here's a new one for $392 http://www.allpartsmac.com/NEW-IMac-27-AMD-Radeon-HD-6970M-1GB-2011-661-5968.htm ?gclid=CjwKEAiAk7O0BRD9_Ka2w_PhwSkSJAAmK…

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Answer 3

babowa

Level 9

78,562 points

Aug 21, 2017 7:21 PM in response to Brian7299

If you cannot boot up at all, I believe it's time to take it to your nearest Genius Bar for an evaluation - they have diagnostic equipment they can run and then tell you what appears to be wrong. It could be a graphics card issue, a screen or logic board problem. Is it still covered by a warranty?

FWIW, that would be a 27" iMac - there are only two models: a 21.5" and a 27".

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Answer 4

babowa

Level 9

78,562 points

Aug 22, 2017 7:57 AM in response to Brian7299

I really do not know as we are all other users here, but I do know that logic boards aren't cheap. If you feel comfortable, you may want to think about doing it yourself by checking out a site like ifixit.com where they show the teardown process and also have some parts.

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Answer 5

Brian7299 Author

Level 1

4 points

Aug 22, 2017 10:46 AM in response to babowa

Ok I will try that.

What part would you say is bad and needs replacing? The logic board?

For about the past week it would work fine and after about an hour the black and white vertical lines would appear like in the previous photos. Now it's not working at all and after it comes on the black and white vertical lines appear

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Answer 6

babowa

Level 9

78,562 points

Aug 22, 2017 10:59 AM in response to Brian7299

My guesses were just that: guesses. Without some diagnostics, I don't know that anyone could come up with anything but that - may be screen, graphics card or logic board related. Have you run the extended Apple hardware test? Yours probably came with Snow Leopard; the test would be on disk 2 if I remember correctly.

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Answer 7

Brian7299 Author

Level 1

4 points

Aug 29, 2017 4:51 PM in response to Brian7299

Turns out it is the Graphics card that's bad. part number 661-5968 and the price for the part alone is about $550. The bad thing is that even with the new card it's only a matter of time before it does the same thing. Apple had a repair program for these imac's and would fix it for free but that program ended June of 2016. End result is it will be a new computer for me but i wanted to post my findings in case anyone else ran into this issue.

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