Possible to connect broken 2011 iMac (functional but blackscreen) to working 2015 iMac with thunderbolt?

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Level 1

4 points

Possible to connect broken 2011 iMac (functional but blackscreen) to working 2015 iMac with thunderbolt?

Hi folks

I wonder if anyone can help me. My research hasn't led to anything useful.

I have an old 2011 21.5 inch iMac that boots up and the screen flashes on for around 3 seconds then goes to black every boot up. I'm pretty sure that the OS is Catalina or High Sierra because I did try to get the most up to date OS as I could for this obsolete machine before this happened.

The screen working then cutting out is odd because it shows it can work but something is perhaps overloading the screen and leading to shut down? I'm not even sure the keyboard works because it's the old type with the loose AA batteries and one of them is stuck - lol. So I've done no hot key solutions or anything, even though my instinct is that its a hardware issue. The keyboard light comes on with new batteries next to the one that is stuck in it.

I have one or two hard drives lying around where I did the time machine back ups so I should have most of the data from the old iMac (as yet unaccessed). What I want to do is access the old iMac and give it one last sweep for old sentimental videos and photos before I junk it because I'm not sure my back ups cover everything.

Can I connect either the 2015 iMac or a basic external monitor to this old iMac and bypass the black screen with a thunderbolt or does the OS on the old iMac have to be newer to do this?

I'd be eternally grateful for any input.

iMac 21.5″

Posted on Jan 23, 2025 8:18 AM

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Answer 1

Top-ranking reply

Servant of Cats

Level 8

45,219 points

Jan 23, 2025 10:27 AM in response to MelonHusk

You can't use the 2015 iMac as a monitor for the 2011 iMac – if that's what you are asking about. Target Display Mode went away when the first 27" 5K Retina iMac came out in Late 2014, and never came back.

You could try attaching a real hardware monitor to the 2011 iMac, and hoping that it works. One issue you might encounter is how to force the menu bar and Dock onto the external screen.

You could also try booting the 2011 iMac in Target Disk Mode, to see if it can act as an external USB disk drive or Thunderbolt disk drive for the 2015 iMac.

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Answer 2

dialabrain

Level 10

137,739 points

Jan 23, 2025 8:52 AM in response to MelonHusk

You could try Target Disk Mode.

Transfer files between two Mac computers using target disk mode - Apple Support

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Answer 3

BDAqua

Level 10

251,339 points

Jan 23, 2025 8:54 AM in response to MelonHusk

Can I connect either the 2015 iMac or a basic external monitor to this old iMac and bypass the black screen.

That should work.but you may have trouble selecting the Main Monitor if Screen Sharing isnt already set up.

See if display works in Safe Mode...

Safe Boot, (holding Shift key down at startup), does the problem occur in Safe Mode? Could take 10 minutes or more.

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Answer 4

Jan 23, 2025 10:34 AM in response to MelonHusk

High Sierra or earlier would be relevant for a 2011 iMac running in Target Display Mode. Given that this 2011 iMac is having screen or GPU problems, I doubt if it's going to work much better as a Target Display than standalone. Note that High Sierra is the newest compatible operating system for all 2011 iMacs, so there's not much chance that the operating system version (as opposed to the broken GPU or screen) is going to cause a problem.

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