Hi all
I have a problem with my 2021 iMac M1 (24")
I’ve returned from a weeks’ holiday (during this time the iMac was off). Booted this morning fine and have a secondary screen plugged in.
Came back a few hours later and when I tried to wake from sleep only the secondary screen came on.
Tried rebooting and now it doesn’t start. I get about a second of the start up chime and then nothing else. I tried disconnecting power and waiting 30 seconds but still no go.
I’m guessing its dead and a trip to the local Apple Store 
https://youtu.be/FprT9ZRF7fM
you may have done this already, I would remove all external connection. Boot up in safe mode and see whether it works
Thanks, but don’t even get the chance - the video above shows what happens when I start and hold the power in. I don’t even get the chance to go in to safe mode or diagnostics.
Called Apple support - they think it’s hardware and I’ve got a Genius Bar appointment for Thursday.
Seriously peeved - the bloody thing is only 9 months old 
Two steps forward and one step back
Pressing the power button REALLY hard restarted the iMac M1 although the Mac screen is completely black
I have the second monitor in and I’m using it as primary display mirrored so nothing is stuck on the blank screen.
I vaguely remember someone once having a problem (on a laptop) where the brightness or something was stuck down low - not the screen dead. I think it might have been ATP? I’ve checked brightness etc and that’s not it.
I’m doing a Time Machine backup and will then do a Carbon Copy Cloner back up (can’t have too many) and then I’ll try a hardware diagnostic (if it can be run from the other screen!)
Will still take it in to the Genius Bar tomorrow…
It has been quite some time when I owned an iMac, but if I remember correctly you are not able to dim the brightness to a degree that nothing is visible. There have been tools to decrease brightness levels beyond the level MacOS provides us with, but I never gave them a try. I think that you still would be able to see something even with the levels all the way down.
I sounds like a hardware failure to me. I have no idea about the laws in Australia, but shouldn’t you be covered by law to get a replacement or a repair for free after just 9 months? All the best for the Genius Bar appointment! 
Learn something new everyday. Dead backlight. Shine a torch in the middle of the screen on startup and you see the logo.
No parts alas at the store so need to take back next week
5 Likes
ok so the wrap up of this saga…
- Screen was replaced - no good
- Motherboard (and therefore SSD drive) replaced - all good now
Restore from Time Machine from Synology NAS went well - just took a while
Back up and running at last
3 Likes