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  1. Thread AuthorThread Author   #1  
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    Default iMac 21.5" black screen on start up

    Hi, almost every time, at least twice, when I start up my 2011 iMac from being completly off the initial start up process happens and then the screen goes completely blank, as if it's turned off, and I can still hear the machine working but can't see anything. I usually have to turn it off completely by holding down the power button and then starting it again. It usually takes at least 2 times of doing this to get it to stay on and allow me to use the machine.

    It also does it some times when waking the machine from sleep. I know this isn't normal.

    Does anyone have any ideas as to what this might be and what i need to do to stop it happening as I may be looking to sell the machine but can't if it's acting up like it is at present.

  2. #2  
    iEd is offline
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    Default Re: iMac 21.5" black screen on start up

    I've read that there is a firmware update available for mid 2011 iMacs I would check Apple's support page for your model.

    #Naked Tuesday
  3. #3  
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    Default Re: iMac 21.5" black screen on start up

    Sometimes the keyboard buttons to dim and brighten the screen acts up too, make sure that isn't the problem. Turn it up as bright as you can 🔅🔆. Mine sometimes goes out and that's the problem. I guess it has a sensor in it and dims whenever the sun is shining in.

    Sent from my iPhone 5S using Tapatalk

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