As you can see in the image the display is showing but it has a white gray problem of not showing the colors correctly.
To fix this problem first you need to open the SAMSUNG LE46B679T2D lcd tv so unscrew from behind.
The problem was in a t-con board that fail so you need to remove some extra screws to get to thim after you have have removed the back of the tv.
Now remve carefully the cables that are connected to the t-con board and unscrew it so you can see where the problem is.
The chip AS15-U INSIDE SAMSUNG LE46B679T2D t-con board needs to be replaced with a new one.
After that put everything back and your tv should be working.
Check this complete video to see how to guide you through the whole process of dissasambly to replacing the chip AS15-U on the t-con board.