iMac 8,1 (2008 alu 24") blank screen

Discussion in 'iMac' started by totallytech, Feb 13, 2013.

  1. totallytech macrumors newbie

    Feb 13, 2013
    Hey Guys,

    I've got a 2008 aluminimum 24" iMac. 3.06GHz, 4GB, 250GB. The screen started to just turn off around 2 weeks ago. Sometimes the machine would power on and work for around 1-2 hours, but sometimes only around 15 minutes.

    The screen just goes black. No funny flickering, no odd pixels etc. Just off.

    The superdrive is still reading etc, if I put in a disk it spins and reads, I can also hear the hard drive reading etc.

    I opened the imac and checked the graphics card. Its the 512MB Nvidia 880GS.

    I sent the graphics card to a company to test it and it worked directly in one of their machines for an entire day.

    I've replaced the ram and the lcd screen too.

    When I power up the machine I check the little diagnostic leds and it shows

    LED 1 - ON
    LED 2 - ON
    LED 3 - ON
    LED 4 - OFF

    but the screen is just black.

    Any ideas - I'm thinking it may be the logicboard but surely the dvd drive and hard drive wouldnt power on?
  2. kpgh554 macrumors regular

    Dec 29, 2011
    LED off- means video card and logic board not communicating apple recommend replace either.{you have.} but have you tested the inverter not problem. and no wires loose or pinched. other than that sound like mother board to me.
  3. totallytech thread starter macrumors newbie

    Feb 13, 2013

    I've not checked the invertor, but I have tried two complete lcd screens - the LCD's have the inverters installed so I'm guessing they are fine...

    If the logicboard / mainboard has failed would the dvd drive etc still power on?


    I have noticed though none of the fans are coming on when I turn on the machine....
  4. kpgh554 macrumors regular

    Dec 29, 2011
    I think dvd drive and hdd powered by psu and only controlled by mother board and fans run by mother board, not sure but someone else may say different.

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