Mitsubishi vs-60801

A friend of mine gave me an old Mitsubishi vs-60801 diamond series rear projection tv and I have noticed that the picture has vertical fuzzy lines. The lines are not always visible and if I adjust the brightness and contrast they get better but don't ever go away. They are real noticable when watching a football game certain parts of the grass looks like it has fuzzy lines running through it. The thing that confuses me is its not the whole field just parts of it that get the fuzzy lines. I thought it might be my cable box but they still show up when watching a dvd, not as bad but there still there. You can still see the picture but there just really annoying. I don't know much about these tvs so any help would be appreciated