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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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iMac Will Not Boot With LCD Installed

Hi, I will preface by saying I fix Macs for a living and am pretty skilled at troubleshooting and diagnosing, but this one has got me a little stumped, so I’m looking for some second opinions.

I have a mid-2011 27in iMac that will not boot when the LCD is installed. It powers on starts loading the boot progress indicator, then goes to a white screen for a couple minutes and reboots. If I take the LCD off and use an external monitor it boots up and works normally every time. The condition is 100% reproducible. Weird, right?

Here’s troubleshooting I’ve done so far:

  • Passes all hardware tests on ASD 3S145A EFI boot disk
  • Replaced video card
  • Installed known good hard drive and installed macOS High Sierra
  • Installed known good power supply
  • Installed known good screen inverter board
  • Alternated pairs of memory to ensure no bad RAM or memory slots

At this point, I feel like it has to be the logic board, but looking for some additional input before I throw more parts at it since I don’t have a logic board laying around for this model.

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Try this, either get the Apple service cable extensions so you can have the display connected but on the side or careful connect the cables but make sure you don't let the metal surfaces touch between the display and the case.

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@danj Thanks for the suggestion. I gave that a try, but unfortunately it did not change the behavior.


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At this point you have either a bad cable or the display its self has a problem. Time to get a replacement to test things out.

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I just remembered I have another mid-2011 machine with a bad video card. Pulled the screen (and cables) and tested, still no dice. Going to swap logic board next.


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Joe will be eternally grateful.
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