Apple iMac 2011 fails to boot - keeps on repeating boot process

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Apple iMac 2011 fails to boot - keeps on repeating boot process

I was wondering of anyone can possible provide some pointers as to why an iMac fails to boot. This is a Mid 2011 iMac 27" and it's not mine, but I tried to debug the boot process and failed to get it running.

The mac in question is over 400 miles away so this is a case of face time and asking them to press keys etc.... This is what I have tried so far:

Normal boot, just keeps on rebooting to the Apple logo and progress bar.
Boot into console mode (Command-V) succeeds and fsck is successful with no issues. Exit single user mode and the machine follows the reboot cycle again.
Boot into safe mode fails half way through the progress bar and restarts.
Boot into recovery mode fail half way though and restarts.

My feeling is that the disk is OK, (family photos on it are backed up by time machine as well so they're accessible) but not sure why it's failing after that point.

If this is the case, would it work in target disk mode so that the data on there can be extracted?

Any pointers would be appreciated

iMac Line (2012 and Later)

Posted on Oct 7, 2019 4:00 AM

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Answer 1

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HWTech

Level 9

69,542 points

Oct 7, 2019 7:32 PM in response to apjimmy

IIRC some 2011 iMacs had faulty GPUs. This might be the problem since the iMac can boot into Single User Mode, but not into any graphical mode. If the iMac has had macOS 10.12.4+ installed, then it should be capable of booting into Internet Recovery Mode (Command + Option + R) which will completely bypass the iMac's internal drive and any potential software or drive issues.

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Answer 2

apjimmy Author

Level 1

11 points

Oct 16, 2019 1:23 AM in response to HWTech

Thanks to all who replied. A couple of final tests I did. I asked to start in target disk mode and it worked, which means that the data are OK for when a new machine is bought and can be transferred across. I sent down a High Sierra USB stick to see if it could boot from that and it sort of did. It appears as a selection in the book menu, and it did boot from it, but after 30 minutes it was still a blank screen, so I think the conclusion about a duff graphics card is correct. I'm asking her not to throw it away as perhaps it can be re-purposed as a 27" graphics monitor at the very least...

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Answer 3

DonH49

Level 6

16,716 points

Oct 7, 2019 5:37 AM in response to apjimmy

could be a pram battery issue. could be a dying internal hard drive

I'd try a boot from an externally connected drive, see what happens.

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Apple iMac 2011 fails to boot - keeps on repeating boot process

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