Imac black screen, external works fine

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

  1. katrienv macrumors newbie

    Nov 23, 2016

    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

    Nov 23, 2016
    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

    Feb 13, 2017

    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

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

    Feb 13, 2017
    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

    Nov 23, 2016
    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

    Feb 13, 2017
    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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6 November 23, 2016