Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Computer Screen Shuts off During Boot Up


My iMac turns on, chimes, then begins booting up but then the screen shuts down during boot-up. I can still hear the fans running in the back but there is no display?

Any of you guys know what this could be?

Thanks, Alex.

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What happens when you connect an external monitor to your system are you able to see your desktop or, use a flashlight and press it to the screen at a sharp angle are you able to see your desktop then?

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Hi Dan so I connected it to a tv and its working through that! When I try the flashlight trick I see no sign of icons behind the glass.

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Last test here: In a darkened rm after the system is started do you see a slight glow in the display along the edge (dark grey just not pitch black). If you do that just verifies the back light circuit is working and only the LCD has a problem.

Jump down to my answer below after you do the test.

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Thanks Dan ill give this a go when my suction cups arrive and let you know how I get on

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Follow this IFIXIT guide to lift the display off: iMac Intel 27" EMC 2429 Display Replacement. You want to check to see if the vertical Sync cable is seated (Step5). You may want to disconnect it and plug it back in.

Did that work? If not, continue the process of taking the display off to get to the display power connection step (Step8) see if its seated, reconnect things and test. Did that fix it?

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@danj hi Dan, I tried these steps just now but unfortunately it didn't help! :(

Do you have any other solutions I should try?


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Leave the power off

Hold down option command P and R

While holding them down press the power button (it will chime once)

Keep holding option command P and R

It will reboot then chime again upon which you can release option command P and R

That should reset your NVRAM

If that doesnt work then i would try shutting down then hold the R key and press the power button, keep holding the R key until you boot into apple's hardware diagnostics menu. From there it will test your system for you and let you know if you have any hardware issues with your machine.

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Thanks for your help.

I tried both these options but no avail. When I tried the first option the screen went on but then went black mid boot. So I unplugged and replugged to try the second option and this time the screen didn't come on at all!

Thanks, Alex

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I've the same problem on an iMac mid 2010 i3 3,06 Ghz : power on, i hear the bong and the sound of the fans and apparently nothing more.

But, i tried to replace the hard drive with a SSD one that i installed on a macbook pro, with an important precision : in this fresh install the session is automatically open.

When i start the iMac, the boot sequence is still with black screen but once the session is up, the screen appears. Very strange.

I tried to switch the screen with a spare : same result.

I'm blocked at this step. The problem is half solved, i would know what is the problem exactly, i don't understand from where goes that.

hope it helps you

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