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Recovery boot impossible / iMac screen goes black

We have an iMac (not the youngest, running Sierra) the screen of which goes black after one or two seconds. This has happened progressively over a few days (black screen at random points in time, then after shorter and shorter time intervals).

We tried recovery boot (CMD+R). That gives us two seconds of screen time, then black screen, then two seconds of screen time again if we touch the keyboard 15 minutes later, then black screen, etc. With this we were able get to "Disk Utilities", and click "Erase Macintosh HD". With this, we were able to navigate to "Reinstall MacOS" and had message "Recovery disk cannot be controlled" (it took a few hours to get through those steps at the available 1s-every-15min pace).

We tried, but unsuccessfully to reboot from the internet with "Option+CMD+R" or "Shift+Option+CMD+R" (with an ethernet connection). In both cases we get the beep, then a grey screen for about a second, then black-out.

We would be grateful for any interpretation and suggestion.


iMac Line (2012 and Later)

Posted on Apr 17, 2021 2:03 AM

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Question marked as Top-ranking reply

Posted on Apr 17, 2021 3:42 AM

It's possible that your iMac is too old to start from Internet Recovery, in which case you would need a startup disc or bootable usb. A mid 2011 iMac that has had a firmware update is required to start from the internet. Exactly which iMac do you have? Identify your iMac model - Apple Support

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3 replies

Apr 18, 2021 7:43 AM in response to SeaPapp

Thank you for your first answer by email.

Our iMac is "mid 2010" - yes, clearly not the youngest [IMAC 27-inch, MID 2010, serial number CK04003NDNP]. Unfortunately we do not have an external boot disk - is it possible to obtain one somewhere ? We have a Time-Machine backup, but to our knowledge that is not the same as a boot disk (?).

More experimenting gave the following behaviors :

Using CMD+F5 we were able to go into audio navigation

Using our television as an external screen, we see a gray background (no menu, no image), but can sometimes (by chance?) manage to drag windows into it. We did not manage to obtain a normal mirroring behavior (we tried Command-Brightness Down). We did manage to drag the Disk Utilities window into the television screen once, and ran "First Aid", then "Erase disk", then "Restore". No success - the subsequent reboot still turns the main screen on (grey) for a brief instant, than goes black.

Anything we could try before giving up? Thank you in advance.

Recovery boot impossible / iMac screen goes black

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