I have a 13 inch Magnavox TV that I use for my bedroom. The TV itself is 6-7 years old. Since a few days ago the TV has been doing something wierd. The picture is completely blacked out except for one small horizontal strip which shows what is on the screen. That small strip is all that you can see of the existing picture. To be quite frank and exact it looks like a huge letterboxing effect is on the screen. This TV is not used for movies at all, it is used as a strict 4:3 viewing screen. What is going on with my TV? thanks.