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2010 iMac chimes but switches off after switching start up disc.

My iMac is normally fine but when I changed the start up disc today from High Sierra to Sierra it refused to start. It chimes and the light grey screen with progress bar opens but after a few seconds it switches off. It's the same when trying to start in safe mode. I thought it might be heat but it's the same even when cold.

Posted on Aug 4, 2022 3:18 PM

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7 replies

Aug 4, 2022 4:40 PM in response to cadplan45

See if you can boot into the Recovery volume in Sierra (boot with the Command + R keys held down  - Intel Macs) or  (How to Boot an M1 Mac into Recovery Mode).


If successful select Disk Utility and run First Aid on all Sierra volumes available. If you get an error indication repeat until no error is reported. Then try rebooting normally into Sierra.  


If you still can't boot into Sierra reboot into the Recovery volume on Sierra and reinstall the system. That will reinstall the system without overwriting the user data.


Aug 9, 2022 3:19 PM in response to cadplan45

Just an update on this one, I took the iMac into an Apple Genius Bar today and they managed to boot it up by holding down alt and then doing a few hardware tests, they showed that the hard drive was fine and they managed to reinstall the Sierra OS, it took a while but it's back up and running again now. Hopefully this might help someone else.

2010 iMac chimes but switches off after switching start up disc.

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