27' iMac (2011) Screen turns off

Is this the solution, finally?

http://9to5mac.com/2013/08/16/apple-opens-graphics-card-replacement-program-for- some-mid-2011-imacs/

9to5Mac is reporting that graphics cards of MY2011 iMacs will be replaced free - Apple is finally admitting there's a problem.

My iMac (same problem as all of yours) was fixed by Apple free a while ago, but not without a fight. Hopefully this will solve quite a few more problems for people.

Good luck!

Thanks ChristopherES: It certainly won't be the solution for all; my machine does not qualify. It doesn't meet their serial number range. BUT... let's hope this does lead to Apple finally "discovering" that a significant screen blackout problem does exist in many of their mid-2011 iMacs.

I have not reported in for a while; I've been performing a long-term experiment. But now I want to give out this FINDING to those following this thread. Last February I had to cough up the cash and purchase a new iMac. I use mine professionally and could not tolerate the screen blackout issue. This "freed up" the problem machine and allowed me to do some experimentation that I could not otherwise (as I sat in my very dark room, attempting to see the image with minimum screen brightness and internal fans clocked out)! I did try the "max screen brightness" that some have used as a work-around, but it didn't work for me.

Since the problem started only AFTER I upgraded to Mt. Lion (some had the problem start with their Lion upgrade), I thought I would try to re-image the machine with it's native OS, Snow Leopard, Mac OS 10.6. I dug out my install discs, re-partitioned the drive, and installed a pristine Snow Leopard image. I did all the Apple updates for that OS (through Software Update) and then gave the machine to a friend to use, and use as hard as she could. I explained the issue and she has been using it a lot, at varied screen brightnesses.

To date she has had only two screen blackouts... of sort... after almost 6 months of use. But these blackouts have not acted like our common problem because she was able to JUST TOUCH the power button and the screen instantly popped back on. In other words, she did not have to invoke genuine "sleep" and then wake the machine OR reboot the machine. It was as if the video display went into normal display sleep, but she was using the machine actively each time this happened and I had her check to make sure that she didn't have a "sleep hot corner" set up.

The bottom line is this: with the native Mac OS 10.6 running, the problem seems to have disappeared! NOW... IF WE ASSUME THAT THE PROBLEM IS REALLY WITH THE LCD BACKLIGHT PANEL (which seems to be the sensitve componentry) then we can PERHAPS conclude that some code in the later OS upgrades—perhaps graphics cards driver code (???)—is causing the hardware failures. Obviously something in the new OS code is precipitating this issue.

Thanks for all who have contributed to this thread. Obviously this IS an Apple issue, but for those of us who forgot/or didn't purchase the AppleCare extended warranty, it has become our problem, at least for the present.

Regards to the Thread,

Mark Byard

Ponca City, OK USA

<Email Edited by Host>

As an update:

Apple store kept my iMac for over 1 week and states they could not replicate the issue. They would not test it with my RAM because they said 32GB is not supported in the mid-2010 released iMac.

They concluded it must be my RAM even though it was functioning properly for the past 2.5 years and passed all memory tests. I was told I would have to put in Apple Certified RAM and replicate the issue for them to take another look.

I asked Apple what type of testing they did and they claimed they tested it with different sleep settings and could not replicate the screen black out issue. They also claimed that they did not have the CGXSetWindowBackgroundBlurRadius: Invalid window 0xffffffff error come up at all in the console when I called to check. They did not clear the console and this error in fact showed up 4 times during their testing. The sleep settings were set to NEVER for both display and computer sleep... making me believe they did not in fact test with "normal" sleep settings. The problem is so random that you actually have to sit down and use the computer for typing text documents, e-mails, watching youtube, etc for the problem to start happening. Then it happens a few times in a row... sometimes once or twice, sometims 5-10 times.

Earlier this evening, I put in 4GB of Apple original Samsung RAM.

With less than 2 hours of total use (probably less than 1) with the 4GB of RAM, the iMac screen has gone black twice. This is still a fresh install of Mountain Lion as I did not want to restore from TimeMachine only to have the problem recur. I am trying to capture it on video again with the 4GB.

To make matters more confusing, the console did not have the CGXSetWindowBackgroundBlurRadius: Invalid window 0xffffffff error the last 2 times it blacked out.

I'm beginning to wonder if

device_generate_desktop_screenshot: authw 0x0(0), shield 0x0(0)

OR

device_generate_lock_screen_screenshot: authw 0x0(0), shield

is the culprit.

CONSOLE LOG containing 2 blackouts at 12:15AM and 12:20AM

8/22/13 12:15:23.193 AM coreaudiod[113]: Disabled automatic stack shots because audio IO is active

8/22/13 12:15:56.931 AM WindowServer[88]: Created shield window 0x95 for display 0x042735c0

8/22/13 12:15:56.936 AM WindowServer[88]: device_generate_desktop_screenshot: authw 0x0(0), shield 0x0(0)

8/22/13 12:15:56.957 AM WindowServer[88]: device_generate_lock_screen_screenshot: authw 0x0(0), shield 0x0(0)

8/22/13 12:16:16.007 AM coreaudiod[113]: Enabled automatic stack shots because audio IO is inactive

8/22/13 12:16:16.000 AM kernel[0]: Wake reason: PWRB (User)

8/22/13 12:16:16.000 AM kernel[0]: Previous Sleep Cause: 5

8/22/13 12:16:16.000 AM kernel[0]: 9042.897044: setDISASSOC from ATH_INTERFACE_CLASS disconnectVap

8/22/13 12:16:16.000 AM kernel[0]: AirPort: Link Down on en1. Reason 8 (Disassociated because station leaving).

8/22/13 12:16:16.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:16:16.000 AM kernel[0]: 9042.933439: setDISASSOCIATE ****STA SYNC DISASSOC SUCCESS

8/22/13 12:16:16.227 AM WindowServer[88]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1

8/22/13 12:16:16.244 AM WindowServer[88]: Created shield window 0x96 for display 0x003f003d

8/22/13 12:16:16.244 AM WindowServer[88]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1

8/22/13 12:16:17.051 AM configd[17]: network changed: v4(en1-:10.0.1.16) DNS- Proxy- SMB

8/22/13 12:16:17.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:16:17.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:16:17.000 AM kernel[0]: AirPort: Link Up on en1

8/22/13 12:16:17.000 AM kernel[0]: 9044.202272: apple80211Request[10310] Unsupported ioctl 181

8/22/13 12:16:17.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:16:17.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:16:17.000 AM kernel[0]: AirPort: RSN handshake complete on en1

8/22/13 12:16:17.480 AM hidd[54]: MultitouchHID: device bootloaded

8/22/13 12:16:18.288 AM coreaudiod[113]: Disabled automatic stack shots because audio IO is active

8/22/13 12:16:19.847 AM coreaudiod[113]: Enabled automatic stack shots because audio IO is inactive

8/22/13 12:16:28.763 AM configd[17]: network changed: v4(en1+:10.0.1.16) DNS+ Proxy+ SMB

8/22/13 12:16:28.771 AM mDNSResponder[46]: 24: Could not write data to clientPID[-1]() because of error - aborting connection

8/22/13 12:16:28.775 AM mDNSResponder[46]: 24: DNSServiceGetAddrInfo v4v6 9-courier.sandbox.push.apple.com. PID[-1]()

8/22/13 12:16:28.775 AM mDNSResponder[46]: 28: Could not write data to clientPID[-1]() because of error - aborting connection

8/22/13 12:16:28.777 AM UserEventAgent[11]: Captive: en1: Not probing 'Apple 1516' (protected network)

8/22/13 12:16:28.779 AM mDNSResponder[46]: 28: DNSServiceGetAddrInfo v4v6 14-courier.push.apple.com. PID[-1]()

8/22/13 12:16:28.780 AM configd[17]: network changed: v4(en1!:10.0.1.16) DNS Proxy SMB

8/22/13 12:16:28.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:16:29.460 AM airportd[825]: _doAutoJoin: Already associated to “Apple 1516”. Bailing on auto-join.

8/22/13 12:16:29.472 AM airportd[825]: _doAutoJoin: Already associated to “Apple 1516”. Bailing on auto-join.

8/22/13 12:19:06.338 AM coreaudiod[113]: Disabled automatic stack shots because audio IO is active

8/22/13 12:19:06.872 AM coreaudiod[113]: Enabled automatic stack shots because audio IO is inactive

8/22/13 12:20:07.530 AM WindowServer[88]: Created shield window 0xa4 for display 0x042735c0

8/22/13 12:20:07.530 AM WindowServer[88]: device_generate_desktop_screenshot: authw 0x0(0), shield 0x0(0)

8/22/13 12:20:07.540 AM WindowServer[88]: device_generate_lock_screen_screenshot: authw 0x0(0), shield 0x0(0)

8/22/13 12:20:24.000 AM kernel[0]: Wake reason: PWRB (User)

8/22/13 12:20:24.000 AM kernel[0]: Previous Sleep Cause: 5

8/22/13 12:20:24.000 AM kernel[0]: 9278.160443: setDISASSOC from ATH_INTERFACE_CLASS disconnectVap

8/22/13 12:20:24.000 AM kernel[0]: AirPort: Link Down on en1. Reason 8 (Disassociated because station leaving).

8/22/13 12:20:24.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:20:24.000 AM kernel[0]: 9278.199077: setDISASSOCIATE ****STA SYNC DISASSOC SUCCESS

8/22/13 12:20:24.226 AM WindowServer[88]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1

8/22/13 12:20:24.228 AM WindowServer[88]: Created shield window 0xa5 for display 0x003f003d

8/22/13 12:20:24.228 AM WindowServer[88]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1

8/22/13 12:20:25.051 AM configd[17]: network changed: v4(en1-:10.0.1.16) DNS- Proxy- SMB

8/22/13 12:20:25.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:20:25.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:20:25.000 AM kernel[0]: AirPort: Link Up on en1

8/22/13 12:20:25.000 AM kernel[0]: 9279.468678: apple80211Request[10310] Unsupported ioctl 181

8/22/13 12:20:25.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:20:25.000 AM kernel[0]: en1::IO80211Interface::postMessage bssid changed

8/22/13 12:20:25.000 AM kernel[0]: AirPort: RSN handshake complete on en1

8/22/13 12:20:25.449 AM hidd[54]: MultitouchHID: device bootloaded

8/22/13 12:20:36.377 AM configd[17]: network changed: v4(en1+:10.0.1.16) DNS+ Proxy+ SMB

8/22/13 12:20:36.385 AM mDNSResponder[46]: 28: Could not write data to clientPID[-1]() because of error - aborting connection

8/22/13 12:20:36.389 AM mDNSResponder[46]: 28: DNSServiceGetAddrInfo v4v6 45-courier.push.apple.com. PID[-1]()

8/22/13 12:20:36.389 AM UserEventAgent[11]: Captive: en1: Not probing 'Apple 1516' (protected network)

8/22/13 12:20:36.000 AM kernel[0]: en1: BSSID changed to 00:1e:52:78:01:d5

8/22/13 12:20:36.403 AM configd[17]: network changed: v4(en1!:10.0.1.16) DNS Proxy SMB

8/22/13 12:20:36.646 AM airportd[843]: _doAutoJoin: Already associated to “Apple 1516”. Bailing on auto-join.

8/22/13 12:20:36.657 AM airportd[843]: _doAutoJoin: Already associated to “Apple 1516”. Bailing on auto-join.

8/22/13 12:20:36.667 AM airportd[843]: _doAutoJoin: Already associated to “Apple 1516”. Bailing on auto-join.

8/22/13 12:21:13.984 AM coreaudiod[113]: Disabled automatic stack shots because audio IO is active

8/22/13 12:21:14.518 AM coreaudiod[113]: Enabled automatic stack shots because audio IO is inactive

8/22/13 12:21:40.789 AM coreaudiod[113]: Disabled automatic stack shots because audio IO is active

8/22/13 12:21:41.324 AM coreaudiod[113]: Enabled automatic stack shots because audio IO is inactive

_______

I'm also not sure if the WiFi issues are back but to a lesser degree. When I wake from sleep, I have to wait about 20 seconds sometimes for the iMac to reconnect to WiFi. At least I don't have to turn off WiFi and reconnect it at random times. I haven't tried to remote access yet since getting this back.

had the same problem. imac 27" osx 10.8.4

caffeine was the solution in my case: app store (https://itunes.apple.com/ch/app/caffeine/id411246225?mt=12).

the app only prevents the screen of going to sleep mode, and even if that was not the problem (i still could hear the sound) the app helped. since i run it, the problem is gone. thanks to my brother who had this idea.

Since I've recently had and solved the problem, I'll weigh in.

Late 2009 27" iMac osx 10.7.5.

First, some observations. I think there is incorrect reasoning in some of the discussions. The most obvious being the assumption that this issue has a single, root cause rather than being a symptom of several potential failure modes. The diverse number of published fixes shows, I think, that there may be several different ways for this problem to occur.

In my particular case the problem clearly was software related and had nothing to do with heat. The screen would go black (not just dim) at random times, sometimes seconds after start up. I could get the picture back by simultaneously holding Shift--Control--Eject and moving the mouse. The screen then would pop back on. If I released the keys the screen might stay on for hours, minutes, or milliseconds. Once the screen went black again, going back to the keys always turned the screen back on, so it could not have been a hardware issue. Further, as long as I held the keys down I could move the mouse and operate the computer. Once I released the keys the problem returned.

In my particular case the problem was solved by doing a PRAM reset (you need a usb keyboard for this) and turning off the screensaver. It's been about two weeks now and what had been a daily problem has never returned.

I don't know if someone mentionned this info but Apple make a Video Card Replacement Program of AMD Radeon 6970M for iMac (27-inch) even if your mac isn't still under warranty or AppleCare:

See: http://support.apple.com/kb/TS5167

I purchased an iMac in September of 2012 with the AMD Radeon 6970M. The issue with the screen shutting of began about 5 months ago. I got around it by reducing the screen brightness to the minimum setting. I waited to take it in because I knew i was still under warranty. I contacted Applecare and they had me do the PRAM reset but it didn't fix the problem. My model was covered under the following program:

Video Card Replacement Program of AMD Radeon 6970M for iMac (27-inch) http://support.apple.com/kb/TS5167

I brought it into my local Apple store and in a week they had replaced the video card, the LCD panel and the LED backlight board. This was completed 3 weeks ago and I have been running my monitor at full brightness since with no issues so far. After this issue and Apple replacing $800+ dollars in parts you can bet that I purchased the extention for Applecare.

I've just had the video card replaced as a result of the mentioned program. I brought the computer home and after 30 seconds being on the screen went black again.

Did any one have a similar situation, or was the random screen blackout resolved for everyone by card replacement?

I had my GPU replaced and as you stated the screen will still go black after some time if the brightness is above 4 notches. Quite annoying, I am hoping that a fresh install of mavericks may help although the issue just might be the IPS panel itself. Here's hoping.

I talked to Apple support right after the video card replacement. I wanted to know if they actually replaced the card. I was hoping for a version number, or something that could be read using software. He convinced me that there is no way to tell for sure unless I can look at the serial number on the actual card inside the computer.

He suggested I took it back to the store so they can look at the screen, or some other hardware part replacement. I told him that I was able to isolate pattern of entries in Console Log when the blackout happens. When he looked at the log he agreed that this might be a software problem and suggested I do "Archive and Install".

I didn't have time to do that yet. However, last night I installed the latest OSX 10.9 (Mavericks) hoping this would fix the problem, since I believe it's a software problem, rather than screen itself.

Unfortunately, the problem persisted. I'm not sure if doing "Archive and Install" would be any different. I was hoping installing a new OS would effectively have the same effect.

For what it's worth, the console log entries pattern is somewhat different that under 10.8:

23/10/13 10:58:12.303 AM loginwindow[1517]: find_shared_window: WID -1 23/10/13 10:58:12.303 AM loginwindow[1517]: CGSGetWindowTags: Invalid window 0xffffffff 23/10/13 10:58:12.303 AM loginwindow[1517]: find_shared_window: WID -1 23/10/13 10:58:12.303 AM loginwindow[1517]: CGSSetWindowTags: Invalid window 0xffffffff 23/10/13 10:58:13.088 AM loginwindow[1517]: ERROR | -[LWBuiltInScreenLockAuthLion closeAuthAndReset:] | Attempted to remove an observer when not observing

Under 10.8 console log looked like the ocmputer is trying to go to sleep when the blackout happens, even though I was in the middle of typing or moving the mouse.

After months of dealing with this issue, it still is not fixed. My machine is essentially useless, so I have not even restored it. The first step I had to do was decrypt the hard drive, so then I shortly thereafter did a fresh install because I am not supposed to use a decrypted hard drive anyway. I can't conduct web based meetings on a computer that could black out at any second... sometimes multiple times in a row.

I took my machine into the Apple Store 4 times (I think, maybe 3?) and they could not accept my videos of the issue as "evidence". They also said they could not reproduce the issue and needed clear steps on how to reproduce it. Obviously I can't give steps on a random issue.

Here's what my screen blackouts were blamed on (none of which fixed issue)

TRIP 1) Hard drive encryption - I decrypted, which took 24 hours

-Did not fix issue, so I installed the OS over my files

-Did not fix issue, so I deleted everything and did a fresh install, which is how it sits today. I only installed a few programs like Chrome (which was also blamed).

TRIP 2) Third party RAM / too much RAM (32GB installed) even though it worked from the day I got the machine and passed all tests - they kept the iMac for over a week and claimed they did extensive testing, console log says otherwise. (Maybe they didn't realize I can tell when the computer was turned on and off). I reinstalled the original Apple RAM

CALL A) Advised to do TimeSnoops and DataCaptures. I was in the middle of moving to a new location, completely new ISP, new Apple Airport AC... and since I was moving, I dropped it off to the AppleStore with the assurance that they would do extenive testing.

TRIP 3) Apparently the RAM not in the "factory" slots (even though it worked fine without error).. so they said they swapped the slots around and "extensively" tested it again. They were supposed to also do TimeSnoops and DataCaptures for Apple Support during their extensive testing. Console logs showed the computer was only on for 2 hours during the ~5 days they had it. They said they could not reproduce the issue, and blamed it on the "environment" at my home. I was upset and didn't even notice the new scratch on the iMac base at first. I got the scratch notated on my account. As I have lugged this iMac around to Apple Store so much, the box handle even broke/snapped off. Luckily they iMac did not drop/break!

CALL B and on) Cannot be environmental issue because I am now in a completely new location, with a completely new ISP, wireless router (Airport with AC wireless), etc. I never bought that argument in the first place.

-Now they want more timesnoops and datacaptures. I comply.

-Chrome, one of the only programs I have installed, is blamed as culprit.

-I uninstall Chrome and avoid using it. Issue still occurs

-More TimeSnoops and DataCaptures

-They could not accept videos in the past, but now they want video evidence. My old videos weren't enough. They wanted videos of it happening under certain conditions like low ambient light, etc. I comply.

TRIP 4) After moving, I am in a location without an AppleStore nearby. I just dropped my iMac off to an authorized repair center.. and apparently they are taking a shot at replacing the screen, led backlight, and power supply. I admit I am concerned given that there are numerous posts pointing to these components plus video cards, logic boards, etc being replaced without a fix. Supposedly they are replacing the scratched "foot stand" part as well.

I also sent timesnoops of wifi/network issues and bluetooth dropout issues with apple mouse and keyboard. I'm not sure if they are replacing the wifi module and/or bluetooth module... or if I have to go through even more troubleshooting steps for these annoying but less debilitating conditions (e.g. I can plug it into ethernet, but having a cord stretch across the room and up the back of the desk sort of defeats the point of having an "all in one" that looks nice sitting on your desk).

Overall, I am shocked at how terrible this "AppleCare" has been after reading about other people's great experiences. I have lots of Apple Products (laptops, iPads, iPhone, AppleTVs, etc), and had been thinking about getting more. This experience really has me really opening my eyes to other alternatives. I had a DELL XPS with warranty that had issues and was repaired within a week... by someone who came to my home to replace parts!

Months of lost productivity on my main "desktop" is just unacceptable. Can I get by with my laptop and iPad? sure... but the whole reason to have a desktop with a huge screen is because it makes me more productive.

Just wanted to share my experience. Overall I've probably spent at least 30-40 hours of uncompensated time trying to document and fix this issue for Apple. What a waste.

Hi, I hope you find this information useful:

A few years ago, we purchased iMac 27" 11,3 (Mid-2010) (with i7 2.93Ghz, ATI 5750 1GB VidRam, etc.) for our offices and software development team. They were originally shipped with Snow Leopard and worked as expected and without any problems. However, a year later, we upgraded to Lion and all of machines immediately exhibited the same problem: the screen would go to sleep by itself and would require a hard reboot or sleep on/off. (Only the screen was asleep and the rest of the iMac continued to function; this was confirmed by screen sharing to the machine.)

Due to the severity and impact on our business, we immediately contacted Apple and their genius bar staff in New York/SoHo. They were unable to determine the root cause, so they replaced all of the logic boards, video cards, and screens, and got us back online asap. This resolved the problem, but we were curious to know why. After days of rigorous testing, we concluded that the issue is caused by a bug in MacOS. Specifically, faulty Kext files (Kernel Extension files extend the functionality of the MacOS Kernel) for the ATI drivers. So, why did the replacing the hardware work? We think that the Kext files that were released and distributed with Lion (and later MacOS versions) correctly supported the newer hardware revision of the replacement components, but not the older ones.

If you're experiencing this problem, short of replacing the components or waiting (for another 3+ years) for Apple to hopefully fix their OS software, you can lessen the effects and be able to recover faster by doing the following: (Please bear in mind that these are not permanent fixes.)

1. Turn on "Hot Corners" and assign one corner to "Put Display To Sleep". When your screen goes to sleep, move your mouse (which still works) to that assigned screen corner for a second, then move it again. This will wake your screen. You may have to do this a couple of times, but it's much faster than a hard reboot or a sleep on/off for your iMac.
2. Turn the brightness of your screen to a low setting (10%-15% of the total brightness).
3. Turn on screen sharing, so you have a last resort method of accessing the machine.

If you're not convinced that it's a MacOS software problem, then do what we did and see for yourself; install Windows 7, Windows 8, or Linux via Bootcamp or as the only OS on the iMac. Those operating systems and drivers worked flawlessly for us; the bug does not occur and the screen does not go to sleep, but if you dual boot and switch back to MacOS, the bug reappears because the iMac is loading faulty Apple MacOS software.

Good luck!

Hi guys, I will share my story and where i am with this same issues.

I got an 2011 27" with all the maxed specs shortly after they went on sale, about a year ago I started noticing a black stain building up on the screen but it was only noticiable when i had a certain shade of gray in the background so i thought at first it was just dust then i could clean the glass and it was gone (well it wasn't gone, the backgroun color had changed from switching applications so it seemed gone).

Eventually the stain became more pronounced and all of a sudden the display started going off randomly. I started freaking out because this is my bread and butter (i'm a graphic designer & web developer for a living) so at this point the display also started to dim on the left side so the left was darker than the right and also flickering started to happen, needless to say i was scared and extremely angry, here's my $3,000 investment only a year old at the time failing on me, when i bought it i ddin't have enought credit to buy apple care so i said "ill just buy it on the other card tomorrow" and i forgot so no applecare.

After browsing the internet trying to fix the issue i decided to send an email to Tim Cook's public email address not being an *** but just telling him how dissapointed i was that this is an issue many have and they still haven't acknoledge.

About 2 days later I got a phone call from Apple's Corporate something (i can't remember exactly) a very nice and helping guy spoke to me and asked me what was wrong and he would do whatever he can to help.

After explaining the situation to him he said he would call me in a day or 2 so i thought "yeah right".

The next day he called and said because i was not under warranty i can't take it to the apple store to get it fixed BUT that they contacted a local certified repair shop and apple would pay for the out of warranty repair and that he had spoken with them and it was all set up all i had to do was drop it off.

I was the happiest person on earth! i brought it to get fix and they replaced the display, they said it was defenately the display going bad and being faulty and after that my display was bright and beautiful again, it took a week but it got fixed and i didn't spend my days angry and scared.

Now about a year after that my display turned off by itself, my frist thought was "not again!" well sure enough the display started flickering and now it turns off by itself. I've searched the web for a fix again and again everyday for the past 2 weeks and i have tried everything and nothing works, the display is faulty or it's the software.

This is making crazy and now i need to figure out a way to get this fixed so i can sell it and buy a mac pro with some other brand monitor because it is unacceptable that this keeps happenning, i was extremely lucky that i got the help i got but i doubt it will happen again.

I will continue looking for solutions and i will come back to this point if i find any solutions.

My two cents...My 80-year old father has a late 2009 iMac. On Saturday, he told me that his screen keeps turning off, and it's been happening daily for a few weeks. I went over there, booted into safe mode, lowered the screen brightness, upgraded to Mavericks, and:

• his screen has remained on with no issues so far
• he says his iMac is running better than it has in a long time (yes, an 80-year old saying it's "zippy")

I have found that Mavericks has brought new life to my kids' 2008 iMacs...my father's iMac still could have a hardware issue, but so far, so good.

Caffeine seems to do the trick for me too but haven't tested it long enough to be sure.

Symptoms: iMac screen goes dark randomly. iMac is still running. Can see very dim image when illuminated with flashlight.

"Workaround" was what mwp13 did: "Turn on "Hot Corners" and assign one corner to "Put Display To Sleep". When your screen goes to sleep, move your mouse (which still works) to that assigned screen corner for a second, then move it again. This will wake your screen."

It is NOT a temperature problem in my case. I stress test the iMac by playing six movies at the same time (mpeg, mp4, avi; in QT Player, QT 7, MplayerX) as well as doing "yes > /dev/null" several times in the terminal.I can see in the ActivityMonitor that all 8 cores are running full blast, the temperature of the CPU is at 89 deg celcius, and everything runs just fine. On the other hand the screen used to go to sleep just idling.

I DO believe mwp13 that it is a problem with the graphics drivers. Does Mavericks have different ATI graphics drivers on the iMac? Is it possible to use these in Snow Leo?