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

the secondone has a different layout too...

i don't know if it is a wrong picture or if it is really a different one.

But i am sure that i read of two different factory that produce PSU for our late 2012 and up imac.

is it possible that shutdown occours only with liteone one?

All was good for a few days, then last night, it shut down again. This time I noticed that the temperature of the CPU (per Hardware Monitor) was about 125F. It seems to run ok below this temp. Has anyone else observed this?

Thanks,

Hank

I suspect this is a "total power draw" problem, that the power used for the processor, the internal hard drive, Bluetooth, and external devices, is exceeding the amount the power supply can provide.

I suggest if you post, list Bluetooth status, wireless/wired, and speed, along with all external devices, whether the are powered by a brick or hub, hard drive type, and processor.

MIne for example, Mid 2011 iMac, Bluetooth off, wireless N 5 GHz, internal WD Black 2 TB, two FireWire external drives, both on power bricks, 2.5 GHz 2400S processor....

Note that their appears to be two motherboards, one supporting 65 watt processors, and one supporting 95 watt....

And another thing I'm noticing. It seems to be a temperature issue as well. I just added Macs Fan Control, and suddenly, in the evenings for some reason, the temp will rise to about 130f on the CPU A (hardware monitor) and the power draw will increase, then it's shut down time.

Is the temp rising due to the power supply or what?

Comments, please.

Thanks,

Hank

ElBartolomeo wrote:

the secondone has a different layout too...

i don't know if it is a wrong picture or if it is really a different one.

But i am sure that i read of two different factory that produce PSU for our late 2012 and up imac.

is it possible that shutdown occours only with liteone one?

Hi Elbartolomeo,

I think I have found out there are 2 brands of the power supply Liteon and Delta:

Liteone : PA-1311-2A

Delta: ADP-300AF T

I am still asking some of seller in Aliexpress to explain what is the difference between these two. However, apparently the ifixmaccomputers are the Delta one.

Glasguy,

today I added an SSD into the blade slot of my iMac 27 2012 and now I run 8TB HD with 1TB SSD without shutdowns today.

During the installation I checked my PSU - its from Delta (Model: ADP-300AF T).

During the last weeks (I was running my system on a single SSD) I had no shutdowns as well.

What did I change?

- 1TB HDD to 256GB SSD (until today, now I run on 2 drives - see above)

- started to switch off the iMac over night (I never did this before)

- skipped my Superdrive DVD from being attached always

- OSX 10.11.6 installed from scratch

Until now I dont have any shutdowns over the last 4 weeks. I will drop a line if a they come back.

Just wanted to let you know!

Cheers,

Nick

Hi Nick,

Would you be able to let me know what is the model of the SSD blade. As think I am going to upgrade in once when I swap out the bad PSU.

Cheers,

Lune

Thanks for the update Nick,

I can confirm that the PSU that is replaced was also the Delta (Model: ADP-300AF T).

All going well with my iMac since replacing the PSU.

Best

Thank you too for your update.

Which PSU you are running now? A new Delta or the liteon?

Cheers,

Nick

Thanks for the great information.

I have 128G fusion drive already as a fusion, look like the people using dual connections to boost the speed up to 900Mbs. I may consider that in the future.

I just bought the Samsung 850 Evo 1Tb SSD. I am planning to install this SSD when I swap out the PSU.

Also, The PSU I have bought is a Liteon, and I am still waiting for its arrival.

The reason I bought the Liteon, because most of the iMac PSU are found as Delta. I suspect Delta has more issues than Delta, I just give it a try.

I will do some stress test once I installed the Liteon PSU. see how does it go?

Regards,

Lune

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.