Previous 1 2 Next 16 Replies Latest reply: Mar 9, 2014 1:33 PM by twoehr
RRMyIMAC Level 1 (0 points)

my 8 month old iMAC 27" quad core machine recently started to "black out"  Screen goes black for no reason and the only remedy is to hit the power button - usually twice.  This will bring the system back to where it was, all open APPs etc. will be exactly where you left them.   I also tested the speaker volume up/down keys to see if the "system" was still functioning during a screen black out.  THe CPU etc. is still avtive as the speaker volume when maxed out will "beep" at you. 


I called tech support - they had me do some special resets of power control and PRAM - no luck


I took the system into Apple store for Genius Bar appointment - 2 hours of running the mac in the store, of course it did not black out....however, they ran other diagnostics and ran a bunch of utilities, graphics etc. to max the RAM and CPU load, heating up the system but still nothing happened.  they suggested I reistall the OS by doing a hard boot and holding down the command key to prompt me to re-install the OS from the "cloud".  This did not solve the problem either.


I then took the system back to Apple and told them to fix it or replace it.  They kept the system for 5 days, and replaced

item 661-5948 Board, Logic, 2.7GHZ, Quad Core i5

item 661-5967 card, video, AMD radeon HD 6770M, 512M

item 661-6615 LCD panel 27 inch with BLC

and labor: TOTAL COST $1183.32


This was all under the first year warranty so I did not have to pay for this out of pocket.  If you look at the list of repairs, they effectively gutted my iMAC except for the HDD and enclosure.  Ahhhhh at last I thought I would be back to a fully functional iMAC.   Two days after getting home and just browsing the internet the blackouts started again.


Once the system blacks out the first time (which appears to be a completely random amount of time) it will then black out more frequently after hitting the power button. 


It's time to call Apple again and demand a new system, wondering if the iMAC LCD crystal / video components are suffering from a manufacturing it seems the new components they replaced are suffering from the same issue.



APPLE - would appreciate you recognizing this problem and working on resolution.


Share holder and completely converted MAC power (family) users!!!!

iMac, OS X Mountain Lion (10.8.1), Screen Black Out
  • NathanL1192 Level 3 (780 points)

    Hi there,


    This seems like a really frustrating problem. Be nice on the phone, and of course they will replace the computer for you. Really sorry to see you have such a difficult time with this computer, you're right that it may well be a graphics/video problem.


    I reccomend doing the following when your screen is blacked out:


    Create a System Diagnostic report. You can do this using the special key chord Control-Option-Command-Shift-Period. Press these keys all at once when your computer is in the problematic state.


    It may take a few moments for the report to generate. Once data for the report has been gathered a Finder window will open to reveal the report file. It will be named something like sysdiagnose_Aug.09.2011_08-47-27.tar.gz.


    If your computer has become completely unresponsive you will need to reboot your system. Once your computer has restarted locate the diagnostic file. You can do so as follows:


    - use cmd-shift-G in the Finder to bring up the "Go to Folder..." dialog

    - enter /var/tmp as the path for the folder you want

    - locate the sysdiagnose file in the resulting Finder window


    Give an Apple Genius this file, and let them study it.




  • rkaufmann87 Level 9 (55,283 points)

    You are not addressing Apple here, they do not read nor participate in these forums. If you are in the USA please call 800-767-2775. This is a customer service number, not tech support it's more of a customer advocate phone number. Be polite, organized, and make your request. They will probably send you back to service but if you are persistent you may get the machine replaced.While the machine is still under it's 1 year warrant get AppleCare to extend the warranty to 3 years.

  • Flex Jargon Level 1 (0 points)



    I just dropped of my 27" iMac for the exact same problem. Bought mine in Jan `12. Did you get your resolved?

  • lenn5 Level 4 (2,530 points)

    Call Applecare and then asked to be transfered to Customer Relations. Tell them everything you've been to with your iMac. Be as detailed as possible.

  • emnem Level 1 (0 points)

    We are having the same exact issue.  Took it in to the Genius Bar on Friday and they ran diags for three days and found nothing wrong with the hardware....which makes believe it's a software bug.  You are correct in that the system remains functional while the screen is blacked out.  I have some remote destop software and can still access and use the iMac while the screen is blacked out.  Also the fact that it didn't peek it's head while they ran diags would be a strong indicator that it's the OS that is the culprit.  I just hope someone can identify a patch or an updated driver to prevent this from continuing.

  • mwp13 Level 1 (0 points)

    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!

  • GV19 Level 1 (0 points)

    I'll add my twopenneth here, after  days testing an imac 27, swapping out the PSU I still have the same  issue. The screen goes dark on test (not a graphics issue) as it  continues playing videos from you tube I can hear the sound but there is  no rfesponse from keys or mouse. The computer will stay active for a  long time (overnight) and can be seen in network but can not be directly  accessed. The system is only two years old.


    I  am frankly at my wits end with this issue I cant get any screen image  on an external using an adapter. using tech toolsv7 shows no issue with  any aspect of the system. Do I change the graphics card or is it  something else?


    Why no comment from Apple on these issues? - very very poor service!

  • girlsonboard Level 1 (0 points)

    I've had the screen blank problem, took the IMac in twice, got home, still not fixed.


    But they used their own keyboard in the shop and couldn't reproduce the problem. I switcheds keyboards and so far so good.


    I'll keep folks updated. Don't get a new graphics card before you try a new keyboard.

  • RRMyIMAC Level 1 (0 points)

    to Grisonboard


    My problem continues and have taken my IMAC 27 back to apple / genius bar.   Even after having the hardware guts replaced, the system continued to have the Screen Black OUT and now its a regular occurrence to the point you can use the system


    KEYBOARD REPLACEMENT - we have tried using a different keyboard, (because my wife likes a full number pad....for no other reason) and I can assure you that changing the keyboard did not make a difference.


    the unfortunate part is that the problem does not appear in the store.  wonder if its "temperature" related, as a few other posts have come up and point to Temperature issues.

  • girlsonboard Level 1 (0 points)

    Hey, thanks, I found my lost post. There are three similar threads. Guess the forum management doesn't merge them.


    While your wife is using a different keyboard, is the other keyboard still in the vicinity? Try removing the batteries from your keyboard that came with your IMac and then using the other keyboard. My Mac keyboard doesn't have an off switch. When you depress the on button it only turns on if it is off, but it does not turn on and off. And two mice work at the same time on my computer so I assume the same ocurs with the keyboard.


    In the shop, they use their own power cords, keyboard and mouse.


    I don't think everyone is necessarily having the same problem, but so far with this other keyboard, I've gone 3 days, no blackouts. I can't say for sure this is the problem though I am going to take my keyboard into the store rather than using it again to see if the problem recurs.


    A person in one of the other threads took his keyboard batteries out and has now gone 12 hours without a blackout.


    But my problem manifest itself after I was home using the computer for a week or more. First time I took it in and got a new hard drive (which was failing and was on the recall list). A week or two at home and the black screen recurred.


    Took it in again and they were unable to recreate the problem. They blamed it on software and reformatted the new hard drive 'again'. I reinstalled files but no aps.


    Another week and it happened again. This time I tested the volume control and verified the computer was still on, only the screen was off. My son suggested testing the screen brightness control on the key board, which seemed to work. But then it dawned on me, you can turn the brightness all the way down and you have the symptom. And they use a different keyboard in the shop where the problem did not recur.


    I switched keyboards with an old one I still had. It's been working since. I don't know. Could be the problem will recur in a week or two. OR, could be it is the keyboard. It would explain why the geniuses are not finding the problem.

  • girlsonboard Level 1 (0 points)

    Forgot to add, temperature did not affect my problem. I tested for that, hot and cold it still occurred.

  • Mcpro-User Level 1 (0 points)

    I got the same Problem and I have always three Days no Problem. But it is bound to what I do. I can force this Screen Blackout with any embeddet Youtube Video. So it seems for me also a Solution to stay away from Youtube. But the Hot Corner Solution from "mwp13"  works well. So it is not Random. It is bound to your Internet behavior.


    And some additional Information: On my Macpro it comes with the last OSX Update. So Apple is highly involved.

  • Mcpro-User Level 1 (0 points)

    I have it even more exact it is not Mavericks. Our beloved OSX is acquitted. This goes to the account of Adobe and Flash. It came with one of the Flash Updates. But with the latest update it seems to be then corrected again.

  • girlsonboard Level 1 (0 points)

    And yet I've done nothing with Flash whcih was not reinstalled after my second hard drive reformat yet the problem recurred.


    And my MacBook which has the complete restore from Time Machine and would have had the problem Flash version but it has not had any problems. I enable flash to watch certain videos on the notebook, but keep it disabled in between. It was causing a screen crash or Net freeze which did not cause the computer to blank out.


    I think I loaded an Adobe update since then but it would have been on the IMac as I didn't own the MacBook at the time.So the MacBook has whatever was on the IMac from Time Machine and that was the same when then problem occurred.


    After the second reformat, the only apps I reloaded were Word and Scrivener. The blank screen returned.



    I do think people are having different problems with the same symptoms.

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