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

Hi all

Just an update, after around 2 months now with the new PSU I have not had a random shutdown, yet :-)

I have also tried to leave the iMac on for several days playing music which went fine, and I do not have to unplug the computer from the power outlet.

All in all, still going strong, crossing my fingers.

Last note, the screen seems a bit brighter than before, like others mentioned.

I had my PSU replaced back in May 2016 and since some weeks the shutdowns have re-appeared, exactly like they did the first time around November 2015. Once my iMac is turned on for too long (say a day, in sleep mode) and I work a few hours, it crashes. Unplugging for 10-15 minutes makes it come back to life again.

Unfortunately, I am out of Apple Care now, so I hope someone has any suggestion what can be my best next step. Is there in the meanwhile any update from Apple that this is a real issue impacting certain builds?

My one-month old 27" Retina (Late 2015 model) is doing the hard shutdown thing, with an SMC reset required to start again. Clicking around in Safari will do it, 100% repeatable, just a question of whether it takes five hyperlinks or 50. No way to predict when, but it WILL happen. Does it on all user profiles, in Safe Mode, even on a clean install in a new disk partition. This jazz started a few days ago and is quite infuriating.

It's going back in to Apple tomorrow, after blowing much of the weekend doing tech support chats and going through the many attempted remedies.

Tom

So after a week at Apple, nothing found. The store tech actually had a couple of interesting ideas that I had not explored. He said the SMC can act as a fuse if it senses irregularities through the power input or Ethernet port, and may shut it down as a protective action.

Trying a couple different things now, like a new surge suppressor (just in case, since it was several years old) and connecting through wireless instead of Ethernet. Thus far the problem has not recurred. If it works for a few weeks in this config, will try using Ethernet again to see what happens.

Tom

I've. Even dealing with this too. After two weeks analysis and effort by AppleCare & Genius Bar at local store they are giving g me a new iMac. Apparently Apple admits an issue in the operating system. They are working on a fix but. It there yet.

Just cut the power supply and wait for at least 20mins. After that replug and the Mac should start again.

The key at my site was to switch off the Mac overnight and cut the powerplug completely. That still works fine, no shutdowns since months.

I have the exact same problem. I just retrieved it from the Apple Store. The had replaced my previous hard drive because of the same problem, because my hard drive became fried because of this.

Do I need a new power supply?

— MacGroupie

Hi,

iMac Late 2012, with shut down issue happening randomly, but at least one time per day (and often more).

I had the Delta Power Supply, replaced with the LiteOn Power supply.

No more issue since 2weeks.

Thx for your help guys !

OK, so after Apple replaced the hard drive, which had apparently been fried, I reinstalled all of my software and documents. Thank god for Time Machine.

A few days later it all started again. Imagine my frustration. About four days of work lost, but at least I had my backup files.

Took it back to the Apple Store. They replaced the power supply and the logic board. Less than 24 hours later, so far, so good.

Oh, one more thing. When I brought my machine back to the Apple Store, I told the Assistant Store Manager (we'll just call her "A"), that this was a known problem all over the Apple Discussion boards, and why had they not replaced the power supply in the first place, she said that the techs were not trained to keep up with "Social Media."

So, I guess Apple Discussions is "Social Media."

True story. Not fake news.

Just wanted to give an update as well. I installed the new LiteON PSU and have had no issues for the last 4 weeks. My iMac has been on the entire time and only gone to sleep when not in use. It seems that the problem was 100% the Delta PSU.

For those intimidated by replacing the PSU, it is not a difficult process and only takes about an hour. There are great videos by both OWC and iFixit. If you decide to replace the PSU I would also recommend replacing the HDD with a SSD too. The new SSD has made my 2012 iMac run like a brand new machine (probably even faster than some of the current HDD versions).

Like others on posts found all over by google searches I have this indiscriminate shutting down.

My iMac is a late 2012 A1419 27" i7 3.4MHz with 31GB ram and a 500Gb SSD and 3 TB Seagate HDD.

After trying all the usual tricks (resetting the SMC, PRAM, clean caches etc) I came to the conclusion, independently, that it was the power supply that was the cause of the issue. I am most reluctant to let so-called Apple techies touch the machine. They would just tell me what I already know ... "the ram is non-Apple, the SSD is non-Apple, the HDD is non-Apple" .. you get the picture.

I have ordered a LiteOn power supply from the UK which is a lot more expensive to ship to Australia than the books I purchase from the Book Depository.

I will replace the PSU and the broken hinge (another crappy Apple issue) and a faulty HDD data cable at the same time. These tapered edge iMacs are a bit easier to work on than the older thicker edge iMacs thankfully.

After 18 months of shutdown agony I was very frustrated. The local Apple Shop could never replicate the problem or find anything wrong with the computer.

In the middle of autumn here in southern Australia the problem became so bad that the computer was shutting down several times a day, including when it was asleep with no programs running or connection to the internet or to the Time Machine backup. It also used to sometimes die when I was shutting the machine down.

The straw that broke the camel's back was when it did that during a restart after a system update and corrupted the operating system so badly that Apple Support suggested I wipe the hard drive and reinstall the operating system from scratch. Even getting the existing information off the computer and onto a portable hard drive became a nightmare because the computer would abruptly shut down while I was doing it.

In desperation I decided to do what others have done and get the local Apple Shop to replace the power supply unit. Before replacing the power supply the local Apple Shop tested the computer again and still couldn't find anything wrong. One month later and I haven't had a shutdown.

If you are having this shutdown problem I would highly recommend that you try replacing the power supply first before spending money on replacing video cards, screens, CPUs etc.

You will probably have to insist that they do that first because they will still argue until the cows come home that it is likely to be one of the other components and not the power supply. Given how often replacing the power supply has solved people's shutdown problems that is not always true.

In my case, I installed some fan controller software (called Macs Fan Control) and pinned it to the GPU PECI (whatever that is), so that the fan really cranks when it heats up above 45C. This has greatly reduced, but has not completely eliminated, the random shutdowns (which I still believe are power-supply related but may well have an overheating aspect as well). Eventually I will replace the power supply. This is my newest of about 15 macs at home and work, and it is the most problematic.

Bill, I had Istat Pro installed and looked for heat and voltage spikes before the abrupt shutdowns and never found any.

I even tried cranking up the fan speed to the maximum and the computer still abruptly shut down even though the room temperature was in the range of 5°C - 25°C and none of the temperature sensors were high.