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

I have a similar machine. Late 2012 i7 3.4GHz 32GB 680MX. I got my power supply replaced by Apple Store itself in Istanbul around 10 days ago. I never tried to replicate the shutdown problem in safe mode but I even got the shutdowns on the windows 10 partition and another partition that I created for testing purposes.

Apple Store itself of course couldn't replicate the problem like almost everyone else in here experienced. It's probably down to power supply not being powered on for far too long). But they still replaced the power supply for around 115 US Dollar (340 Turkish Liras)

By the way as far as I'm told it's a 300Watt part. While I was at it I asked them to fit the machine with some other type of power supply made for other, possibly newer iMacs that utilize a higher wattage part. They refused to do so. Apple policies obviously. I haven't asked about the brands of the outgoing and incoming power supplies. I'd do so if I had read the related posts in here.

Long story short, for the past ten days the machine has always been on, I had played Civ V for like 10 hours at once, max. settings and so far no shutdowns. So, tho Apple Geniuses failed to replicate the problem and tho it seems like a problem Apple itself should acknowledge and pay for, apparently the replacement of the PSU resolved the issue.

Hi Lune

Did you have any success with the Liteon PSU, or have you received it?

Also, after surfing around for this problem on the net, it is sad to see post on so many other forums with users facing similar problems. Apple must have a quite bad taste in their mouth, and maybe they just hope that someday all of us have scrapped our machines :-(

Hi Beolion,

Thanks for your post. Well, I am still waiting for the PSU shipping. As I bought it from China (Aliexpress), it is a bit cheaper but take a bit longer. Therefore, I will let you know how does it go for sure.

Well, I guess it is capacitor issue of the PSU. I believe that one of the manufacture which used some cheap capacitor or resistor. Therefore, it wouldn't last very long.

Frankly, Apple should fix the problem immediately, Apple should have the quality assurance to ensure their product up to a standard. Although the Apple care can cover the any failure, my PSU has been replaced by apple once. Howeverm It starts to get problem again after 6 months. I am very disappointed about it. Apple is not fixing the root cause, they just replace the bad parts with the same bad parts.

I'm doing the same thing, I ordered mine from China (LAI YI SHENG) and it has been shipped. Should receive it next week. The the fun begins, I"ve never open up an iMac before, just Air Books, and iPhones.

I began to have this problem recently. I tried SMC reset, Apple Hardware test and NVRAM reset for many times. They won't work. The iMac keep shutting down randomly. It is very frustrated when I am writing code. I found this discussion today. Thank you guys for posting your researches and progresses.

My iMac (27", late 2012, 3.4G) had 2 problems now.

1. The stand broken (Design fault? 27" 2013 iMac stand just gave up!)

2. Shutting down randomly, and won't start again unless unplugging the power cable.

Apple should definitely call users for these to be repaired, before they causes the users so much confusion.

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.