27 iMac (2012) crashes and requires smc reset to turn on

My late 2012 iMac, i7 16gig RAM 27 inches keeps shutting down. It looks like as if it was unplugged. Happens randomly. Sometimes while playing Diablo 3, surfing facebook or using iphotos or other apps. Seems to not crash if just left on overnight and not been used.

In order to turn it on again I have to unplug it from the power line for like 30 seconds, only then it starts.

I have the settings set to restart on power failure, but it does not.

Happened a few times a few months back. I have installed a surge protector and it worked fine for like a month or two. However last 2 days it has shut down like 10 times...

Help would be greatly appreciated. I suspect hardware failure.

iMac (27-inch, Late 2012), iOS 7.1.1

Posted on May 5, 2014 9:44 PM

Top-ranking reply

lisbonbhoy

Level 1

36 points

Posted on Oct 26, 2017 3:46 AM

Hi there - hope I'm on the right thread for this reply.

I recently suffered the same issue for over a week whereby my late 2012, 27" iMac (1TB fusion drive) would unexpectedly shutdown like someone had yanked the power supply cable from the back. I could only get it restarted by removing the power lead for 15 secs, plugging back in and waiting 5 secs before starting up - and apart from a Chrome "unexpected shutdown" message, you wouldn't have known that it had shut off.

I spent a few hours on to Apple Support trying various solutions (Diagnostic test, MemTest, SMC/PRAM resets, Sierra reinstall etc).

By trial and error, I eventually identified the problem's source as being my Satechi 7 port USB 3.0 hub which had 2 x Porsche design (1TG and 4 TB) external HDD's attached, along with 2 x charge/sync docks for iPad and iPhone. Since I removed the USB Hub and plugged the peripherals into the back of the iMac, I have had no issues whatsoever - and my pride & joy is back working like a dream.

I hope this update helps

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574 replies

Jun 11, 2017 1:58 AM in response to bjorn78

I join this club with my late 2012 iMac 27inch. My iMac also won't starts up anymore. This screen appears. Bjorn78 did you solved this problem?

Jun 25, 2017 4:59 AM in response to Beolion73

Hi all

Just an update, 6 months after replacing my PSU I have not experienced any random shutdowns.

And I am not even shutting down my iMac anymore, just put it into sleep mode.

Bill Scott

Level 6

11,465 points

Jul 5, 2017 9:19 PM in response to Lagoiski

I also have this problem.

Is there anyone who has installed a LiteOn power supply who is still experiencing this issue?

Bill Scott

Level 6

11,465 points

Jul 20, 2017 2:53 AM in response to phillat5dock

Thanks for posting your experiences. Please let us know if the problem reoccurs.

FWIW, in the US at least, Apple has been replacing the faulty hinge free of charge.

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27 iMac (2012) crashes and requires smc reset to turn on