Previous 1 2 Next 22 Replies Latest reply: Nov 2, 2013 4:05 AM by mwp13
joparish Level 1 (0 points)

Intermittent black screen. Hard drive, music etc continue running but screen goes black. Restart only works for maybe a minute or two, sometimes only a few seconds. Is this hardware or software related? Definitely getting worse. Apple support talked me through a couple of resets but problem persists. Anyone have a definitive answer to this please?

iMac (27-inch Late 2009)
  • dadioh Level 1 (5 points)

    If you shine a flashlight at the screen can you still see the images on the screen or is it completely black? Trying to determine if it is the LED backlight or the whole display.

  • joparish Level 1 (0 points)

    Hi, yes I can still see images on the screen.

  • X423424X Level 6 (14,215 points)

    Sounds like screen sleep.  Check your Energy Saver system preferences to see if you set screen sleep too short.  Also check Exposé system preferences to make sure you didn't define a screen hot corner to put the screen to sleep and you are "wondering" into that area unintentionally.

  • joparish Level 1 (0 points)

    Thanks. Checked these and settings are ok, but screen doesn't 'wake' when mouse/keyboard used. Someone on here suggested Shift-Control-Eject together which does sometimes bring up a login box, although screen usually goes black instantly you release the keys. Display is working at the moment, having gone black a few seconds after logging on, then returning without me touching anything a few minutes ago??

  • X423424X Level 6 (14,215 points)

    Not sure what to suggest at this point.  You may need to get this checked by apple.  You can try doing a smc reset but I don't think anything will change.

  • joparish Level 1 (0 points)

    Thanks. That's one of the resets Support talked me through yesterday. Fingers crossed it's been on for the last hour or so without a problem! But it does shake your confidence in it, and as I use it for my work it's a pain as well. Thanks for your help so far. I think maybe 'dadioh' who replied first might have some ideas. If it's a hardware issue then at least I can get it repaired I guess - software glitches just do your head in!! Thanks again.

  • dadioh Level 1 (5 points)

    If you can still see images with a flashlight then it is not screen sleeping. Screen sleep will turn off both the backlight and the signals that drive images. Your backlight circuit board is failing which is a hardware issue. If it is under warranty apple will fix it. If not under warranty and you have some skills then you can buy the backlight circuit board. There are guides on

  • joparish Level 1 (0 points)

    Brilliant - thanks. I'll have a look at and see if I can do this myself as machine is out of warranty. Thanks again.

  • dadioh Level 1 (5 points)

    You will need 2 suction cups to remove the glass and a T8 Torx for the screws to get the display off. iFixit has some great guides and they also sell the parts. Just be careful and follow the guides and you will be fine. The biggest pain is keeping the dust from getting between the glass and the display panel. Try and work in a clean environment and be prepared to wipe dust with a microfiber cloth or blow if away with compressed air.

  • joparish Level 1 (0 points)

    Thanks again.

  • zazznpazz Level 1 (0 points)

    What a great question dadioh - been struggling with the same problem for about 2.5 years - or one month beyond warranty.

    my screen sporadically slickers insanely to one or sometimes two corners, goes black and then back on, using a univerally unknown timing system.

    I have just shone a torch at it, and it shows as blank.



    I was just living with it, sharing screens from another mac to control and shutdown - but it's a complete pain in the neck.

    tried changing temperature environment, reinstalled software - twice, SMC, PRAM, you name it, tried it.


    There are so many problems on these forums - seems like duff product.....?


    iMac 9,1

    Intel Core 2 Duo



  • Argomedo Level 1 (0 points)

    joparish you resolve this with change the backlight board ? i have same problem and want to buy a new backlight board.


    Thanks !

  • joparish Level 1 (0 points)

    Er, actually no. It worked for a while, then failed again. New LCD display required! Now works fine... You could try the board, and the cable that links it too, as apparently these can fail. It's a bit trial and error though. You might end up having to change the display, which is quiet a big job and must be done v. carefully so as to avoid damaging anything else. Hope this helps, and good luck!

  • Willem_g Level 1 (0 points)

    Had the same troubles for a couple of months - read all the postings i could find - tried everything with the resetting stuff - and finally decided on a new backlight board. Installed it today. Alas to no avail. I am lost here. 

    Back to square one...

Previous 1 2 Next