Samsung LED TV No picture but sound is working

My LED TV UA48H6400. Sound is working , but there is no picture. Backlights are also off. However, when I removed one ribbon cable going from TCon board to pannel, the back lights came on, but still there was no picture. When I connected it back and removed the other ribbon cable also, the back lights were on, but still no picture. When I connected both ribbons back, the back light went off. Where can be the problem