Previous 1 2 Next 16 Replies Latest reply: Oct 8, 2015 2:50 AM by tyrnanoc
shoehsu Level 1 (0 points)

I got a 27" iMac (intel) a couple months ago (mid-year 2010) and sometimes the screen won't start up after it goes to sleep. Most of the time, I will leave the computer and the screensaver will start then the display will turn off and go black. When I return and hit a button on the bluetooth keyboard or move the Magic Mouse around, the computer will come out of sleep, display will turn on, and everything works the way it's supposed to. However, every now and then, the screen will go to sleep (turn black) and it won't turn back on when I hit the keyboard and move the mouse. I can just barely hear the fan still working, so I know the computer is on but asleep. Even when I hit the power button or hold it nothing happens, it won't even restart. I have to physically unplug the power cord and replug it back in then hit the power button to get the computer to start up again. I have moved the computer around to different outlets and even tried it at a different house, but this issue still occurs. Am I doing something wrong with the Energy Saver settings or is there just something wrong with my computer?



Mac OS X (10.6.4)
  • Michael Hintlian Level 1 (15 points)

    I have precisely the same issue...everything fine on Saturday, Monday screen.  I'm looking for the same support.

  • vmh21 Level 1 (0 points)

    Same here.. stopped working yesterday.  I can not get it to start.  Hope to get some direction as well.

  • Michael Hintlian Level 1 (15 points)

    An Update:


    Last week I had installed 16gb of new ram from Crucial - 4/4gb sticks.  Thinking this was the only variance in my routine I removed the new ram and re-installed the original 4gb of ram the computer was shipped with (Samsung).  Bottom line is that the iMac started right up without trouble.


    I've got an RMA working with Crucial who will swap out the ram for replacement - they believe it is a defective stick. 


    I'm interested if you had made a similar change to your computer (upgrading ram) and if so whether swaping back to the original sticks helped the problem.


    Crucial by the way is excellent to work with, they provided very specific support around the choice of ram that was precisely compatible with my 27" 2.8ghz i7 iMac which is probably why they suspect one of the 4 sticks was defective.


    We'll see.

  • shoehsu Level 1 (0 points)

    No, I haven't changed anything since I got the computer. Everything is factory installed and no one's ever opened it. Are the Apple Geniuses able to fix this? I haven't heard of anyone saying Apple was able to fix this for them.

  • Carolyn Samit Level 10 (102,820 points)

    Try resetting the PRAM first.



    If that doesn't help, try resetting the SMC.


  • Knifedge Level 4 (1,605 points)

    Try booting from the hardware test DVD and running the extended test. Easiest way to do that is insert the disk, reboot, and hold down the "D" key until the test appears. If it finds anything wrong that would be the first place to start.

  • Michael Hintlian Level 1 (15 points)

    Thanks Carolyn,


    My computer was behaving exactly like the original poster, while my screen was black and the box itself was simply giving off a faint whirring sound (the HD running), I tried resetting PRAM but could not get the computer to restart.  I unplugged it fully then restarted but there was no start chime just the faint sound of the HD spinning.  While I think resetting the PRAM would contribute a lot, the computer was disabled beyond the point of that being possible.  Also tried resetting SMC...same problem, no positive restart.

  • durignieux pierre Level 6 (10,625 points)



    try to replace both mouse and keyboard batterie


    try to use if is possible a wired keyboard to wake up computer



  • Meandmydog Level 1 (0 points)

    Hi All,


    I'm having a similar issue however my screen will absolutely not come back on no matter how many times I turn it off and on.  I was in the middle of typing an email and it went blank. I turned it off and then back on several times. I know it was on because I hit the volume up and down keys on my key board and they made the little popping noises that demonstrate the volume loudness. I also unplugged the power cord as someone else suggested. I checked the dim and lighter buttons. 


    Am I missing something?


    It is the new iMac that came out this May. 21.5 inch screen intel core i5. 500 gb.



  • lesliewhaley Level 1 (0 points)

    I've had my new iMac 7 days and it won't come on. I've tried everything I know. 

    Mac people, please respond b it's hard yo get you on the phone!!!

  • anakareniseverywhere Level 1 (0 points)

    Hey did you ever find out the solution?

  • 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!

  • blondie73 Level 1 (0 points)

    I've same iMac 27" Mid 2010

    I've similar but inverted problem !

    Using maverick there's no problem

    Latest Boot Camp:

    Using win 7 & 8 : there's no problem but sleep mode & hybrid sleep mode does'nt work ! NO wake up

    Using win 8.1 : power saving(turn off screen) & sleep mode & hybrid sleep mode does'nt work ! NO wake up


    I've tried also a win tool associated to a key:

    Alt + F1 = nircmd.exe cmdwait 1000 monitor on

    Alt + F2 = nircmd.exe cmdwait 1000 monitor off


    Also the same a can turn off monitor with Alt + F2 but with  Alt + F1 does'nt wake up


    Is there a solution ? I cannot call Apple to change hardware because it's too old..

  • DMP-Westerville Level 1 (0 points)

    Having similar problems, I move the mouse and screen goes black. No apparent way to awake the screen or to fix it with mouse and keyboard connected. Alternate Keyboard and mouse has not created problem so far. Having both keyboards and mice connected (each keyboard in separate USB ports) has not reproduced the problem.


    OS X 10.10.2

    iMac21.5, mid 2011

    8GB ram


    Used mac, but keyboard and mouse (both USB) came still wrapped in cling film as if new and untouched.

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