screen issues

Discussion in 'iMac' started by Scottie51, Nov 11, 2015.

  1. Scottie51 macrumors newbie


    Nov 11, 2015
    IMAC ( 27 inch)

    Processor 2.7 GHz Intel Core i5

    Memoery 4GB 1333 MHz DDR3

    Startup Disk Macintosh HD

    Graphics AMD Radeon HD 6770M 512 MB

    a short time after I turn on my mac the screen starts to dim on the left side, just a little then it will go back to normal and then dim a little. This happens a few times and then the screen goes black. If I walk away and come back later it is often back on, or if I try to turn it off using the off button the screen will comeback on. Not every time. Sometimes I have to hold the button down till it turns off.

    Any ideas of what is going on? Fix?

    iMac, OS X Yosemite (10.10.5)
  2. AppleNewton macrumors 68000


    Apr 3, 2007
    1 Finite Place
  3. DeltaMac macrumors G3


    Jul 30, 2003
    Sounds like your backlight board may be failing.
    Turn the display brightness to maximum.
    Cover the ambient light sensor, which is at the top of the screen next to the camera.
    You should see the screen go much dimmer when the light sensor is covered, and the brightness should remain even.
    Uncover the sensor, and the brightness should return immediately.
    You can change the sleep settings in System Preferences/EnergySaver pref pane.
    Sleep settings can be overridden by external devices, so if you want to see the sleep settings that are unaffected by external devices, disconnect those, particularly USB mouse, and external storage drives, such as you might use for backup.
    Set Energy Saver to sleep at the minimum amount of time.
    It should go to sleep after that time, then stay asleep until you press a key on the keyboard, etc.
    You can have your system set so it sleeps when you press and release the power button.
    Don't hold the button long, as 5 seconds or so will shut your iMac completely off. It's supposed to do that. If you only want sleep, then just a quick press and release will do it.

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