Level 1

51 points

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

Fametown

Level 1

4 points

Mar 5, 2015 5:08 AM in response to Lagoiski

It's incredible. Same problem here! It's clear that this model has a fault. iMac 27" Late 2012. Four times in technical service. It can't reproduce the problem. No solution. In my house 4 o 6 shutdowns every day. Apple please help your customers.

Mar 5, 2015 9:15 AM in response to Fametown

I think we should report this case to Apple directly. Anybody know where we should contact for this matter?

Mar 5, 2015 12:59 PM in response to Fametown

Yes agreed, but what to do with Apple inc .. How can we get them to listen? There must be 1000's of iMac 27" late 2012 with random shutdown issues.

I never played video games and looked after my computer well. Cost near $3,000 new.

Mar 5, 2015 1:00 PM in response to cre8ivepark

Good question.

Mar 5, 2015 2:03 PM in response to cre8ivepark

How about something like this:

iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

Fametown

Level 1

4 points

Mar 5, 2015 2:12 PM in response to vanstar sydney

I have this video card. NVIDIA GeForce GTX 680MX 2048 MB.

Mar 5, 2015 2:20 PM in response to vanstar sydney

My model (A1419, EMC2546) i7 3.4GHz has nVidia GTX 675MX GPU, not AMD.

Mar 5, 2015 5:31 PM in response to cre8ivepark

Guys, Fametown and Cre8tive, - How can we get Apple Inc. to recognise our random iMac shutdowns?

My specific model is the late 2012 i7 27" (13,2) with NVIDIA GeForce GTX 675MX.

It could be a faulty Power supply part problem or Logic board or other?

At any rate it will cost us $ and the inconvenience to repair.

Mar 5, 2015 5:45 PM in response to vanstar sydney

Yes, let's do some research on more direct contact.

Thread about similar symptom on iMac Late 2012 :

https://discussions.apple.com/thread/6176570

https://discussions.apple.com/thread/6432787

https://discussions.apple.com/thread/2473276?start=0&tstart=0

This is my video recording. As you can see, it is sudden black out and need SMC reset to power on.

This also happens on even recovery partition boot, during OS installation process.

https://onedrive.live.com/redir?resid=8DAC765079965977!61357&authkey=!AI0eyx0TWA HHZcA&ithint=video%2cmov

It looks like it is not OS or software issue, this happened in Mavericks and other clean install OS too.

What I've done so far :

- Replaced power supply (by Apple)
- Replaced with new RAMs

- Replaced Logic board
- Replaced HDD
- This is not heat related problem. Temperature is ok. Symptom shows on even cold booting process.
- Sometimes it runs ok for one or two days.

Now remaining parts are CPU, LCD and cables. I believe CPU fault or bad LCD is the least suspicious thing.
I am trying to replace power supply connector cable (connects power and logic board).
Also I will try replacing display signal cable.

RubenBCN

Level 1

12 points

Mar 6, 2015 2:02 AM in response to Lagoiski

It happens to me too.

In my case I need to unplug the power cord after the unexpected shut down and wait 15 minutes.

Mar 6, 2015 2:03 PM in response to RubenBCN

Yes, same here. 15mins sometimes half an hour unplugged before the iMac restarts.

What model iMac do you have?

RubenBCN

Level 1

12 points

Mar 6, 2015 2:18 PM in response to vanstar sydney

iMac 27" late 2012.

Mar 6, 2015 2:20 PM in response to vanstar sydney

Just a heads up, Seems that the TechTool Pro app can offer some pertinent info on our macs. I have not tried it yet. 99USD.

Here's an email reply just received, where I asked about various possible tests.

'Hello,

Thanks for your email. The new sensors test in TechTool Pro 8 includes tests of a variety of your Mac’s internal sensors, including those related to your power supply. If the electrical output coming across the sensor for your power supply is outside of the acceptable range for that particular sensor, it will trigger a failure in that test.

Thanks,

Micromat Help'

Fametown

Level 1

4 points

Mar 7, 2015 4:21 AM in response to Lagoiski

I just used TechTools 8 and all the tests are OK. Yesterday my iMac shutdown more than 10 times during the day. Brrrrr.

Fametown

Level 1

4 points

Mar 10, 2015 3:08 PM in response to Lagoiski

I just made this video. I use iStats Menus 5 for the sensors.

https://www.youtube.com/watch?v=fal-OzSzF6Y&vq=hd1080

All it's ok just before the shutdown ???

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