Imac black screen, external works fine

Discussion in 'iMac' started by katrienv, Nov 23, 2016.

  1. katrienv macrumors newbie

    Joined:
    Nov 23, 2016
    #1
    Hello,

    I have a problem with my imac.

    what have I done:
    I have a imac 27" late 2009. I had the famous white screen, so my videocard was broken. I ordered a new one. installed that one, imac works fine. I reïnstalled with Sierra and tested the imac for about a week.

    Today I decided that everything works fine so I want to screw back the imac together (some screws inside where not screwed back, so I screwed them together. Connected back the lcd.

    But when I start now the imac I have a black screen on my imac.
    External monitor works fine but nothing on the 27" screen. I see the ligt of the imac goes on.

    When I check in system preferences I see the 27" monitor, I can adjust the brightness (I see the black go more or less dark when I slide the slider). But nothing on the screen.

    I have the same imac from my wife. I tested it out with another screen, same result.
    I placed back the broken graphics card, but not a white screen, but same black screen.

    Anyone an idea what the problem can be?
    The connector on the logic board looks ok, nothing special.
    smc & nvram allready done, doesn't help.

    Any idea?
     
  2. katrienv thread starter macrumors newbie

    Joined:
    Nov 23, 2016
    #2
    In case anyone has the same problem. I found it out myself.

    On the motherboard there was a problem with transistor Q9001, I resoldered the transistor and problem solved.
     
  3. PK003 macrumors newbie

    Joined:
    Feb 13, 2017
    #3

    Many thanks Katrienv!!

    I have been trying to figure out the problem knowing it was not the graphics card, LCD screen, inverter, backlight, HDD, etc. I was narrowing it down and my searches with Google and came across your post. I had no idea where Q9001 was but as I started looking closely at the logic board something out of place came to my attention and when I read the transistor number it matched! I guess because it is located so close to the graphic card tray support arms I must have bumped it when removing the card.

    If you look closely at the picture I have popped the top off it it and it has opened up like a hatch or door.
    Do you think this is fixable or do I need to replace the entire resistor?
     

    Attached Files:

  4. katrienv thread starter macrumors newbie

    Joined:
    Nov 23, 2016
    #4
    I think it will be fixable without replacing.
    Just good soldering skill needed :)
     
  5. PK003 macrumors newbie

    Joined:
    Feb 13, 2017
    #5
    Not sure how to go about soldering it. All three solder joints are still in good order. It's just that the top has popped off. If I was to flip it back over how would I keep it in place or make it all connect again?
     
  6. katrienv thread starter macrumors newbie

    Joined:
    Nov 23, 2016
    #6
    the picture is not very clear for me.
    When the top has popped off you have to replace the transistor I think
     
  7. PK003 macrumors newbie

    Joined:
    Feb 13, 2017
    #7
    Yeah that's what I am in the process of doing, although, it's a pain trying to find out which 2N7002 diode is used on this logic board.
     

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