MacBook - White Macbook screen dim issue

I need some expert advice here. I bought a white Core Duo 2GHz Macbook with a dim screen. You know the drill: you can see everything on screen but it's very dim.

Usually a dim screen points to either inverter or LCD backlight. I tested it with another inverter, no luck. The only extra LCDs in my possession are broken/cracked ones and I have no idea if they work, and I have no extra Macbook board so I can test this current screen. It works perfectly fine with external screen.

So I came to the conclusion that it's either the small cable that goes from logic board into inverter or logic board. The seller insists that GMA 950 videocards had this issue. I googled for a while and I can't find anything on this. Does anybody know if the seller is correct and where I can locate such info?