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ffmed124 Level 1 Level 1 (10 points)

Screen on IMac goes black (just like it went to sleep)  all of a sudden and the only way to get it back on is by hitting the power button.  When the computer sleeps, it will wake by tapping the space bar twice but when it goes black, this doesn't work.  After hitting the power button, the computer will go right back to the screen you were on prior to it going black, nothing is lost and it doesn't have to re-boot.  This started out happening once in a while like maybe once every couple of months, then maybe a couple of weeks, (didn't really pay attention to time frame) now it has happened twice today.  Does anyone have any idea's or suggestions on what may be causing this?  I have not noticed any particular application that was running when it occurs.  Any help would be apprecaited, thank you in advance.




21.5 Mid 2011

Mountain Lion

Version 10.8.2

2.5 Ghz Intel Core i5

4 GB 1333 MHz DDR3

Graphics AMD Radeon HD 6750M 512 MB

iMac (21.5-inch Mid 2011), OS X Mountain Lion (10.8.2)
  • BDAqua Level 10 Level 10 (120,915 points)

    Hi Mike,


    Have you done a PRAM reset, CMD+Option+p+r...



    In fact, do 3 in a row, takes a bit of time.


    Intel-based Macs: Resetting the System Management Controller (SMC)...



    Have you blown the dust out lately?


    Get Temperature Monitor to see if it's heat related...


  • ffmed124 Level 1 Level 1 (10 points)



    Thank you for your response, no I haven't tried anything to correct it yet as I am not real familiar with troubleshooting Mac's like I am with a windows computer.  I will try your suggestions if the problem continues.  It's really kind of odd how and when it occurs, I don't know what the cause could be so I am thankful for any suggestions.  It hasn't happened since I wrote this so I'm going to try and see how frequent it occurs and if there is any particular program that I am running when it does.


    I will keep this thread updated as to the progress or lack there of so I may need your assistance again in the future for suggestions.  Thank you again, I appreciate your time.

  • asterion2 Level 1 Level 1 (0 points)

    I could be wrong but if it is like mine, the screen goes really DARK BLUE not BLACK.

    Mine did this again for the first time in 8 months or so again yesterday. In the past I just

    turned it off, waited a minute or two and restarted without any evident damage being done.


    Here are my Specs :

    Intel Imac Core 2 Duo Model A1208

    2Ghz 2.5 GB memory and I just about a week ago installed 10.6.3 Snow Leopard O.S. that I purchased from the Apple store online for 19.99.


    Mine also develops intermittent Horizontal ( not Vertical ) pixelated lines on the LCD.


    I think they must be related in some way to HEAT. Normally these things happen when my SMC fan Control temp gauge gets up around 125 degrees farenheit.


    There used to be an apple support article number 58270, I believe that gave details as to how to remove the back cover and dust the inside to reduce the heat buildup. I am still looking for my printed copy and I cant find the support article on line anymore.


    I did what I could to blow the dust out from the inside and vacuumn it out, I installed SMC fan control and that for the most part eliminated the problem, however when I installed Snow Leopard they happened again. The lines appeared Immediately and then went away, since it has only been a week I have to keep watching. Then the Dark Blue screen thing happened again, and then for the first time ever a Kernel Panic. I restarted and all seems fine.


    I guess I am saying install SMC Fan Control and set that speed at 2,000 RPM, and see if that helps.

  • kerstin911 Level 1 Level 1 (0 points)

    hey ffmed124,


    have you solved the problem yet? because the text you wrote could be exactly mine as well and I have the same problem... no idea, when it happens. sometimes the screen went black more than twice a day and sometimes one week not..


    so, i contacted the apple support team today and the gave me the advise to look here at the community boards!





  • ffmed124 Level 1 Level 1 (10 points)



    No, I have not solved the problem as of yet, or as far as I know I guess I should say.  The screen has not gone black since my last post.  It is very odd at the times that it did and or does (Not constant).  I am continually watching to see if it continues but I still have no idea of what the cause could be.  Good luck with your search results, I didn't have any luck but then again, it hasn't gone black for a few weeks.  Wished I had better answers for you.



  • v.liessi Level 1 Level 1 (0 points)

    Hey there.

    First, sorry my english. I am from Brazil, and I have this same problem.

    To me, happen when I watch videos. From youtube, VLC, what ever.

    After some minutes whatching videos, my imac turn off. Just it. Turn off. I have to wait some seconds to turn on again.


    What can I do? I have the new iMac, and I buy it 2 months ago.

  • BDAqua Level 10 Level 10 (120,915 points)

    Wow, that new... can you have Apple take a look at it?

  • teos Level 1 Level 1 (5 points)

    I have the same problem and have had it for about six months. Running 10.8.3. have had the Imac back to apple and they can't find a fault. Obviousley there is one. Apple needs to look at this seriously.


  • teos Level 1 Level 1 (5 points)

    I found a fix for waking up the screen without restarting.  Create a hot corner to send the screen to sleep. When the scteen goes dark blue/black, click on the hot corner and press the space bar. The screen wakes up.

    No idea as to why it goes black in the first place yet.

  • ffmed124 Level 1 Level 1 (10 points)



    Thanks for sharing any information you have found on this subject.  I still have not found what the cause could be from.  I was hoping to find that it occurred while doing the same task but that is not the case.  It seemed to quit for a little while but has come back with at least 3 occurrences over the past week.  This is what happens, I will go to my computer which has been in the sleep mode, I hit the space bar to wake it, open Safari and log onto a web page then the computer screen goes black just as if I had turned it off or it lost power, I can hit the space bar and nothing happens and it comes back on within 20 - 45 seconds ( I have not timed it ), then it will run fine for the remainder time I spend on the computer during this occurrences.  So it appears to be happening right after waking from sleep mode.  I will pay more attention to see if it happens during any other time while in use and it does Not happen every time.  I wish I had better answers for any one that is experimenting the same issues but I do not.  I will continue to try and keep this tag updated with anything I may find.  Hopefully, Apple will figure out what might be the cause since more people are experiencing it.

  • fiona.mac Level 1 Level 1 (10 points)

    This happened to me. 27" iMac, built mid 2011. Apple replaced graphics card (no difference), logic board (no difference), screen (no difference), power supply (bingo). Apparently there is a separate cable in the power supply that powers the screen. Replacing the power supply fixed my black screen problem... then I got a white screen problem and Apple replaced the iMac, but hey that's another story... so try your power supply.

  • ffmed124 Level 1 Level 1 (10 points)

    Thank you for the information, I will have to give it a try.

  • glbirch Level 1 Level 1 (0 points)

    I have an 27" iMac that does the same thing.  The screen goes black almost immediately after turning it on.


    When it first started happening it was intermittent and you could not predict when it happened.  I power another monitor off it and it works fine even though the iMac screen goes black.  I also took it into the Mac Store when it first started happening and they told me it works fine, and it only cost me $95.


    It seem if the "geniuses" can't find anything with their diagnostic software, they can't fix anything.


    I now have two monitors off the iMac and it sits on the floor like a regular desktop.  It still runs fine but the iMac screen itself, will not work.  As soon as the machine starts, the screen goes black.


    I have three of these and two of them have had problems with the screen.  One is under a year old and have not had any problems with it yet.  When I called support, they said they have never seen this problem but it is evident that it is common.

  • fiona.mac Level 1 Level 1 (10 points)

    Absolutely the best thing to do is video-record your computer doing it. I did that so that even as an intermittent fault, the technician could see that it was actually happening. Don't know how old your iMac is, but surely there is a warranty obligation for Apple to fix this problem for you.

    Good Luck.

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