is my GPU fried?

Discussion in 'iMac' started by khashper, Nov 27, 2010.

  1. khashper macrumors newbie

    Joined:
    Nov 27, 2010
    #1
    Hi All.

    I hope someone can help me.

    Yesterday I was listening to music on last.fm and my iMac screen suddenly went black and the sound began to peck. There was nothing to do, so I restarted my iMac by holding the power button for 5 seconds. When I turn on my iMac now, the screen is completely black, but I can hear that the computer starts fine and when I get into the OS, I can open iTunes with keyboard shortcuts and listen to music, change tracks and all.

    I have a an external screen hooked up to my iMac but that is also completely black.

    Does anyone have some suggestions about what's wrong? Is the GPU fried since the output to both screens is null?

    Regards
    KHASHPER
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

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    Location:
    Finland
  3. khashper thread starter macrumors newbie

    Joined:
    Nov 27, 2010
    #3
    thank you for the reply Hellhammer. That sounds like an expensive repair :(
     
  4. Harmush macrumors 6502a

    Harmush

    Joined:
    Sep 21, 2008
    Location:
    Liverpool
    #4
    How old is the machine, is it under apple care or anything?

    Try resetting PRAM and SMC, long shot but i am sure that fixed a graphics problem of mine in the past.
    This was a while ago however and wasn't this problem.
     
  5. jons macrumors 6502

    Joined:
    Apr 24, 2008
    #5
    Shut if off and unplug it for a few minutes. Unplug all peripherals from the machine.

    When you boot the computer hold down cmd, opt, p and r. Hold it until you get three chimes. This will reset the pram.

    You should also reseat your ram. I've had at least a dozen instances where ram has caused this symptom. Reseating usually fixes it.

    If you still have a black screen, it's a hardware failure and will need repair.


     
  6. Techhie macrumors 65816

    Techhie

    Joined:
    Dec 7, 2008
    Location:
    The hub of stupidity
    #6
    If it were me, and the machine were out of warranty, the first thing I'd do is check the connection from the LCD to the logic board. Opening the computer will of course void AppleCare, so if you don't know what you're doing, don't wouldn't bother.

    If that cable were to come lose, the machine would turn off, and then display the symptoms you described. Usually graphics cards don't completely fail, and the typical logic board failure disables the computer.

    best of luck
     
  7. khashper thread starter macrumors newbie

    Joined:
    Nov 27, 2010
    #7
    Thank you so much all. I'll try the different things and return :)

    it's unfortunately to old to be under any Apple care...
     
  8. khashper thread starter macrumors newbie

    Joined:
    Nov 27, 2010
    #8
    @Jons: how do you reset the RAM? I've reset the PRAM and that didn't work.

    @Tecchie: I dont think it a loose connection - it happened suddenly and it's not just the iMac LCD that is black but also the external monitor...
     
  9. Harmush, Nov 29, 2010
    Last edited: Nov 29, 2010

    Harmush macrumors 6502a

    Harmush

    Joined:
    Sep 21, 2008
    Location:
    Liverpool
    #9
    Shutting down the machine resets the RAM... Period. RAM is know as volatile memory meaning when there is no power going to it, it can't hold any information.

    Resetting the PRAM (Parameter RAM) resets all settings such as, system time, video settings.
    When you reset this did you hear the startup chime twice? which normally means you have done it correctly.
     
  10. khashper thread starter macrumors newbie

    Joined:
    Nov 27, 2010
    #10
    hi Harmush.

    When I reset the PRAM (holding down cmd+opt+p+r) the computer reboots and I here the startup chime. If I keep holding down the buttons the iMac keeps rebooting and giving me one chime each time (I've tried holding it down for three reboots) - am I doing it correctly or should it chime 2 times on each reboot?
     
  11. Harmush macrumors 6502a

    Harmush

    Joined:
    Sep 21, 2008
    Location:
    Liverpool
    #11
    I think you should hear two chimes, Make sure you are holding the combination of keys before the first time and then just keep holding until you hear another.
    That means the PRAM is definitely properly reset.
     

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