Imac A1311 EMC 2389 No Display

Discussion in 'iMac' started by cequil2, May 7, 2014.

  1. cequil2 macrumors newbie

    May 7, 2014
    I picked up this Imac for cheap (free) and thought I would give it a go to repair it. The first and second lights of the four status lights are lit which made me think it is the video card or logic board itself... So I replaced the CPU with an I3-550 and the computer finally made the startup chime. Then after trying countless times to redo the internal lcd screen connections I connected an external monitor and everything seems to be working besides the internal LCD. I bought a new displayport cable for the internal screen but still no luck. None of the connectors or cables look to be damaged. If you go through the service book it ultimately leads you to replace the LCD. Before I go and spend money on an lcd screen, I would like to know if anyone else has any other ideas...I have reset the smc/pram, replaced the hard drive, took the battery out and checked it, took the graphics card out and checked, just don't know if there is much more I can do. I did test the LED Power inverter board and the logic board is not sending the signal to turn on the back light. Could this be a defect on the logic board itself or is this because the logic board doesn't communicate/see the lcd panel connected? Would this signal originate from the graphics card? I see on one forum someone had a similar problem and they hard wired a 3.3V signal to turn on the lcd from the logic board to the inverter board. However, I am not sure if I do this, if there will be video on the screen if I do get it to turn on.
  2. cequil2 thread starter macrumors newbie

    May 7, 2014
    Anyone know how the LCD communicates with the logic board? What does the V-Sync do and what does the LVDS cable do?
  3. dtjay7 macrumors regular

    Jul 25, 2008
    N. CA
    Did you ever get this working. I am have a similar problem. I have it working with an external display but the internal will not work. I have replaced the logic board, LCD panel, and LED driver board. I am running out of choices. Power supply?? GPU??? Everything works great except the internal display. Thanks for any help.

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