# imac 27" black screen



## joeybham (Sep 3, 2011)

imac 27" Model A1312 / Late 2009 / 2.66Hz i5. 

i bought if faulty the imac powers up ok and does work ok on a external display useing the mini port cable from the imac to my tv.

however the imac lcd it totally black.

i have used a flashlight to see if i can see a faint image but cant see anything its totally black.

 i have replaced the invertor board but it did not cure fault.

i have noticed theres 3 leds are on on the logic board.

anyone help.


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## DeltaMac (Sep 3, 2011)

You need to make the room as dark as possible, to see if there is any glow at all from the display. If you have already done that, and there's no faint glow at all, then try reseating the flat display cable the connects from the LCD panel to the logic board. If you then still have no video, and no faint image, then try replacing that cable. If you just get 3 LEDs, and #4 never comes on, then the logic board is not communicating with the display panel - another reason to try reseating or replacing the cable (it's called an internal DisplayPort cable.) If that doesn't help, replace the LCD panel. You've already verified the video card, because an external display works. Hopefully, the cable will do it. If the display panel is bad, then you have a decision to make, I suppose - it won't be cheap.


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## Iuse Free (Apr 15, 2016)

Hi, 

did you ever find what was wrong with the black screen? I have the same problem on the same model.


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## DeltaMac (Apr 15, 2016)

Iuse Free said:


> Hi,
> 
> did you ever find what was wrong with the black screen? I have the same problem on the same model.


If you read my post #2, that is a short number of steps to decide what is wrong with your iMac video.

If you don't want to open the case, then all you really need is to shine a bright light into the screen, looking for any video that might be very dim.
Then, connect an external display to discover if ANY video is coming from the graphics card. If you get external video, then the graphics card is likely good.
If the internal screen stays black, then the backlight controller has failed. That part is called an "LED Backlight Board".


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## Iuse Free (Apr 15, 2016)

thank you for replying. it works with external monitor fine. am reading on apple forums and i want to finalize my thoughts about either a backlight board OR a small connector that runs 6 wires to fire up the led.

thank you


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