Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor

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Black Screen iMac, external working changed backlight board

Hello,

I'm having an oddly specific problem with my iMac.

I have a couple fixer uppers that I am working on, and I put a new GPU in one and put everything together only to find that the LCD wasn't working, though everything was working through external monitor and all four LEDs on motherboard were lit.

I pulled the LCD from my other computer, which I confirmed was working before switching. The LCD was still completely out, so I scavenged the Inverter board as well, which yielded nothing.

To be clear, the screen is completely dead, and I wasn't able to see my desktop at all when I shone a light on it, so I don't believe its simply a backlight problem.

Any help would be greatly appreciated as I'm not sure where to turn at this point!

Answer this question I have this problem too

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First hook it up to an external monitor and see if the GPU is generating a signal.

UPDATE

Your best bet at this point is to replace the LED driver board:

iMac Intel 27" EMC 2429 LED Driver Board Replacement

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I have and the computer is fully functional through the external monitor. I can detect the GPU (radeon 6790 1GB VRAM I think?) on about this Mac on the monitor as well.

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Sorry, I guess I had my terminology wrong in the original question. I pulled a working LED Driver Board and installed it to no avail.

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What is the voltage in your outlet please?

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Anna, let's solve your problem first, please.

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standard US outlet, 120 volts 60 HZ though I don't have a way to electrically test that

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Joseph Rushkin will be eternally grateful.
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