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

Have you tried to restart in safe mode? This is working for us while we await our new power supply.

Hi Just it,

as far as I can report - I started to began shutting down the iMac during night.

Since this day not a single restart during day.

Weeks later I replaced the Hard Disk (original 1TB HDD) and now its a killing machine.

I had this problem and I remember how frustrating that was. I just went off during writing or in the middle of a game.

It began when I used Safari. I then switched to Firefox and didnt had this shutdowns for 1-2 weeks. I thought I got it but then I shutdown while I was draggin the speaker volume to low. I clicked on the icon and swwwooosh - the mac was off and I wasnt able to bring it back.

Well - it works for me to shutdown and ! totally unplug the powercable off the wall ! during night.

Since then I also had it up and running 2 nights because of backups and copy jobs but it was running the next day very well.

Just try that if you can and see if the things are getting better.

And let us wait for the guys changeing their PSUs.

Cheers,

Nick

I will try the safe mode, thanks Hank. Also I'll try Nick's method. Thanks.

Hi all,

I solve my shutting down issue.

Replaced the PSU, the old one was a DELTA, the new one installed now is a Liteon.

I inspected the old one and it showed some signs of heating on the circuit board.

New PSU has been on for more than a week now, iMac has been on all the time, used it for a bit everything, movies, gaming, did a benchmark test to stress it a bit...

all good no shut down.

cheers

Nick

Nick,

Good news. Thanks. My new PSU should be here in about a week. Did you have any issues opening up your iMac? I've read the iFixit instructions and have bought the tools but are still nervous.

Thanks

Hank

Hi Nick

Thanks for the reply, really hope it solves your issue, others as well. Please let us know regularly how it goes.

And looking forward to Hank's experience as well.

By the way, I have replaced the RAM and hard drives on two AirBooks and replaced the screen on an iPhone, but this looks more complicated.

hi Hank,

yes it is more complex, i followed the ifixit guide. Be careful not to touch anything on the PSU ! Also the power cables have clips on them. You'll need to press them in order to disconnect the PSU.

If you don't feel confident, get a IT tech to do it for ya.

cheers

almost 2 weeks, no shutdown !! 😉

Thanks ngrant,

I'm more concerned about opening and removing (and replacing) the screen than the components. I feel good about that part.

In the meantime, we pull the plug every night and that seems to help. Also upgraded to Sierra (10.12) yesterday.

Hank

PS wish that PSU would get here.

Bought a Late 2012 Refurbished iMac in 2013 and it was working great until a couple months ago this problem started happening. Seemed to be at random times (even in sleep mode). Took it to the Apple Store out of warranty three times... The first time they replaced the power supply (~$120). It worked fine for about a week, then the problem started again. Took it back in a second time and they replaced the logic board (~$325 - they credited me $200 for the power supply repair). It was fine again, for about a week...

Yesterday I dragged it back in to the Apple Store, got a manager instead of getting in line for a Genius... He talked to the techs in the back and we agreed that they would try changing the casing of the iMac (at no charge). He had me wait a couple minutes for the iMac Genius to check it in for the repair. He came over and asked me what was going on (like this was the first time I was in), so I told him about this experience (pleasantly, though I'm sure he could tell I was ******). He read the repair history, went in the back to talk to the techs, then came back and offered me a brand new Late 2015 iMac - with slightly upgraded specs (including 5k retina!!!) - at no additional charge (other than what I've already paid). They even offered to upgrade it more, if I wanted to pay the difference in cost.

I instantly went from extremely frustrated to Christmas morning. I hate the process of having to wait in the genius line when returning a repair, and especially dragging a 27" iMac through the mall several times, but they do back up what they do.

'Safe mode' works, but refreshing rate is very low, programs like browser refresh all the time. Programs without many GUI elements are ok such as iTerm.

'shutdown iMac during the night' doesn't work for me. The next morning, after using for 1 hour, iMac turns off by itself.

Hi Guys,

Finally, I have got the PSU and installed it yesterday. The process is very straight forward. I would considered it is just medium level installation. I have got the OWC kit, for special torx screw drive(T9, and T10), some adhesive tape and a guitar pick. I also have bought thermal sensor from OWC for the SSD Hard Disk. The turnaround time for the process around an hour.

I have found out the defected PSU is Delta brand. I have replaced the Liteon one. It works quite well, but need to observe it a bit more . I will do a further report about it. In addition, I have also installed the Samsung SSD as the hard drive. I need to create a fusion drive with the default factory SSD. It shouldn't be too hard.

These are the photos taken last night.

https://www.flickr.com/photos/146342873@N02/sets/72157674444595115/

lune-cheung,

Awesome work on this. I have been following this for a long time and still have the issue but was hoping to see someone take the leap and do it right I agree replacing parts with bad parts was always my take on it too. Hey can you email me the correct items/tools please striper134@gm**l.com I would like to order all parts today and get this finally finished so I can use this expensive paperweight for anything other then surfing the web for 15 minutes.

Hi FalseAlbie,

Thanks for your compliments. I better share the parts we should need for the fix and upgrade.

Removing the the Screen tools (if you are NOT upgrade with SSD)

OWC General Servicing Kit

https://eshop.macsales.com/item/OWC/DIYIMACGEN/

Power Supply Unit

Liteon - 300W PA-1311-2A
https://www.aliexpress.com/item/New-Original-300W-PA-1311-2A-Power-Supply-For-Ap ple-iMac-27-A1419-2012-Year-661/32531015…

SSD (Optional)

Samsung SSD or Whatever SSD you want

newertech adaptadrive - https://www.bhphotovideo.com/bnh/controller/home?O=&sku=798867&gclid=Cj0KEQjwsai _BRC30KH347fjksoBEiQAoiaqsWuimAWES6w39JRS_Vt0QzxaiK2pDY3wNlsYQiLA0wMaAodE8P8HAQ& Q=&is=REG&A=details&pcur=AUD

OWC In-line Digital Thermal Sensor for Hard Drive Upgrade (All the tools and thermal Sensor for apple hard drive) - https://eshop.macsales.com/item/OWC/DIDIMACHDD12/

I'm another late 2012 27" i7 iMac with 16GB DDR3 RAM and NIVIDIA GTX 680MX 2048 Mb graphics card owner who is experiencing these random spontaneous shutdowns. Usually when I'm doing OpenGL renders, but occassionally when I'm doing nothing.

The problem started 2.5 years after purchase and progressively got worse. The local Apple dealer couldn't find anything and for 4 months afterwards over winter the computer has been fine. The problem has started again now notwithstanding that the ambient internal day time temperature here is mostly less than 20°C and lower than 10°C at night. The AHT I did the other day says everything is fine.

I am losing work and time and I am very unhappy that a relatively expensive computer looks like it is no longer usable after just 3.5 years.

Like others I would be happy to pay to fix the problem if I knew for sure what the fix was. I am not prepared to gamble on Apple's current solution of lets progressively try replacing components in the hope that will cure the problem though.

Apple need to step up to the plate and tell us how to fix the problem.