Boots, but goes to a black screen
I've just had gotten another replacement logic board for my 2009 25.1" iMac. I press the power button and I hear the chime. The LCD screen lights up white, then goes black (yet I can tell that it's still backlit). The official tech manual claims the logic board has 4 LEDs at the bottom, but there are only 3, and all 3 are lit up. I've tried resetting the PRAM, but nothing happens. I've connected an external monitor, nothing changes and there's no video on either screen. I've tried connecting an external monitor without the LCD screen attached, There's still no video, and only LEDs 1 and 2 are lit.
It's my assumption that there's something wrong with the onboard video card. If not, then I'm absolutely stumped. I've been getting my logic boards from ebay, and have had the same issue with the video card.
I have another logic board, but with a functioning video card and no LVDS port. (Some genius ripped it off. It functions fine with an external monitor attached. Every now and then I'll see a seller offer a repair for the LVDS port. I'm tempted to try that. If I could, I'd just swap video cards, but Apple uses glue to hold them in place.
Any ideas or suggestions would be greatly appreceated.
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