Chosen Solution
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 diskReplaced video cardInstalled known good hard drive and installed macOS High SierraInstalled known good power supplyInstalled known good screen inverter boardAlternated 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.
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.
