Projection Sony Tv, Model Kp-7220 I Have A Sony Rear Projection Tv Model KP-s4112u?

I have a Sony rear projection tv model KP-s4112u? - projection sony tv, model kp-7220

The problem is that we are after a while the television is the picture starts from right to left, tries to roll to the wall, turn left, so a few minutes and take off again, but the problem is still there, anyone who any idea what the problem is that I do not want to, I thank you friends TV.