27' iMac (2011) Screen turns off

I have had this and tried every possibility including getting apple to replace the graphics card under the rather hidden replacement program on that part. Nothing worked including the graphics card replacement till I finally replaced the backlight board ( part no will be one of these...661-5980, 605-3034, 605-3035, 612-0094).

Only two days so far but it seems fixed at last. It was turning off as fast as you turned it on before.

Backlight board is about £120.

4 Days now since changing the backlight board and still OK. When it went off before you could still see the image on the dark screen if you got at an angle with light reflecting from a lamp. This showed that the problem was the backlight and not the display or graphics card or software so I am fully convinced about the backlight board being the problem and fixing it bears this out.

Hi, I also have a mid 2011 27" iMac that has exhibited these symptoms.

FRom rom reading the posts on this thread I think there are two distinct problems, firstly where the backlight stops working and the screen images are still visible under a strong light. Secondly, where the screen goes black and may be able to be resumed by using Ctrl Shift Eject sequence. My experience relates to the latter.

My screen would go black however the computer was still running, using Ctrl Shift Eject would restore the screen initially. I turned on Hot Corners and used this method however the problem became so severe that neither of these methods would work. The screen would come on for 2 seconds and then go dark again.

I had read someone else's post that removing their third party memory allowed their system start working normally. I did not believe it but thought I would give it a try. I am surprised and happy to report that my iMac is now in its third day without the black screen problem when I was lucky to go for an hour before.

i can't explain it or even come up with a decent theory. I had an additional 8 gb of memory which I removed to produce this result.

I've been having this problem for several months now with my 27" mid-2011 iMac. After much searching around the web I tried adjusting the brightness to maximum, then minimum, then back to where it roughly was every time I switched the computer on, woke it from sleep or noticed any kind of flickering on the display and, fingers crossed, it hasn't happened for over a week now, whereas it had been blacking out every few hours at worst and not coming back on without a hard restart. The automatic brightness adjustment seems to be working fine too.

Anybody from the Philippines here?

I bought a pre-owned iMac 27 mid 2010 model. When I tested it from the seller's house it was working fine. When I configured it at home it was ok, until 2 days later I counter the same problem.

I brought it to a local Service Center but the tech there found nothing. He said my iMac is working well.

My iMac is now back home and suffering the same problem.

I have had this and tried every possibility including getting apple to replace the graphics card under the rather hidden replacement program on that part. Nothing worked including the graphics card replacement till I finally replaced the backlight board ( part no will be one of these...661-5980, 605-3034, 605-3035, 612-0094).

the trick is to shine a torch at a very acute angle at the black screen and see if the picture is there. If you can see something then the problem is with the backlight.

If its not the backlight then talk to apple about the free graphics card replacement (there are two schemes for different criteria)

Now been running fine for months.

Backlight board is about £120.

Well Apple needs to get honest and admit it is an engineering issue. I have just spent the last hour reading about the same faults as I have had for the past 12 months. As a once proud Apple user having purchased 5 phones, 3 ipads, 1 imac 27, and a 15 inch mac pro I swear I will never buy another apple product again. I finally took my 27" imac into the genius bar and was told that I had to replace the logic board ($800 plus!!!!) to resolve the black screen "sleeping" issue.

I was so disappointed that I was tempted to smash the unit in front of a full shop of prospective Apple customers !!!!!

We need to start a social campaign to Apple to help solve this issue. I would even be happy to pay 50% of the cost.

I will try the brightness issue and see if that solves the problem, however as a final -cut user I will heat up the unit quickly.

Off to the shops to buy a new PC, at least I would be able to repair it.

Good luck to all Apple sleepers for 2015

Just downloaded smcFan control and set ODD to 3700rpm and adjusted brightness to 50% and so far no blackouts !!!!!!

Here's hoping that might work. STILL very disappointed in Apple's attitude.

Try adjusting the brightness and install software smsFan control to speed up display fans as it seems like an overheating issue.

SOLVED!

I had the blackscreen/blackout issue (not the backlight) after I added RAM. I had added 2 x 4Gb and kept the 2 x 2Gb in the original slots. I now had 12 Gb.

The blackout issue started shortly after this.

After reading the post (below) I took out the 2 x 4 Gb and replaced them with 2 x 2 Gb from another Mac I had lying around. This gives me 8 Gb with 4 identical DIMMS in the slots. The Black screen did not occur again, no matter how I try to recreate it changing the brightness, screensavers and/or sleep mode.

I think the RAM solution makes sense, so far working for me, problem looks solved. Try it and let us know! Thanks Sunfiresaturn!

Sunfiresaturn including Apple logo changes for feature 126 Apple image including Apple logo changes for feature 126 Apple image ends here

Jan 19, 2014 5:03 PM

Re: 27' iMac (2011) Screen turns off

in response to Ashadur

[DocumentBodyStart:b21f0b0e-bbb6-4d8f-827a-58c825f45ac6]

All of your symptoms were indentical to mine and I tried EVERYTHING to fix it.

My realization?

RAM

I have 4 slots open in my 2010 - iMac

2x2GB DDR3-10600

2x4GB DDR3-10666

For some reason, my iMac couldn't handle both together. At first I thought it was the 10666, but then tried both RAM types separately, and both work.

I guess you shouldn't pair 10600 with 10666 - or at least different ram sizes.

I am going for 4x4GB 10666 now.

I hope this helps everyone because I was losing my mind for a short while.

iMac is happy and on full brightness.

Life is good.

SOLVED!

Thank you so much! You were right, it's a RAM issue. As of Lion the system handles memory differently hence the occurring issue.

I made sure I now have 4 equal DIMMS in the slots and the problem dissapeared!

So everyone: check your dimms and make sure they are EXACTLY the same. It may even be worth installing a brandnew set in case one is faulty. 4 x 2G will run Yosemite just fine!

That's great to hear Captain. Unfortunately, my ultimate solution was not long term.

The problem came back. I tried everything.

Had to buy new iMac. Fingers crossed it's just an isolated case.

Good luck!

I have the same issue and I'm fairly certain it's not a memory issue as I have 4 slots of equal ram.

I'm leaning toward an engineering flaw that apple doesn't want to step up to and admit.

If Steve Jobs was here he would most likely take care of this huge issue personally. So we now have

a different type of Apple now so it seems.

I run smcFanControl and keep my monitor at the lowest display brightness and so far it has stayed on

long enough for me to write this post at least. So I hope this can help what I have posted here.

I'm feeling a "change.org" petition coming on!

*L

My Specs:

iMac (27-inch, Mid 2011)

2.7 GHz Intel Core i5

8 GB 1333 MHz DDR3

AMD Radeon HD 6770M 512 MB

I'm feeling a "change.org" petition coming on! ( I wonder how many people would back that? hmmmmmm)

Maybe it's my calling to be the El Capitan and steer this ship into battle?!?!?! I'll need me mate's tho arrrrg!

Call me El Capitan Blackout! the righteous pirate of the black seas!

*L

My Spec

iMac (27-inch, Mid 2011)

2.7 GHz Intel Core i5

8 GB 1333 MHz DDR3

AMD Radeon HD 6770M 512 MB

I just experienced the black screen this morning on my 2 month old 27", 5k. Called the 'genius' guys and they had no clue. Since I had unplugged it to take it in for diagnosis, on a lark, I plugged it in to a different outlet in my kitchen. It booted right up. Then I tried another outlet in the living room and it booted up again. Finally, plugged it in back at my desk and it started up and is running fine. I don't get it and am now waiting for the proverbial 'other shoe to drop'. My long held faith in Apple is being sorely tested.

Thanks for letting me vent.