Hitach Ultravision Rear Projection 50 TV, bad image

Dad gave me his old tv which worked fine, but after moving it to my house there is a problem with the picture. The picture is fine then for unknown reason it shrinks down from the top and bottom. If I hit the TV (some times you have to hit it hard) the image corrects itself. What causes the image to change? Thanks!

I hae seen this before when moving rear projection
t.vs what probably happenend was something either got loose or a bad connection sometimes even a crack in the board sounds like the problem is in the vertical circuit.

I will look tonight, but if it cracked the that sucks, I tried to strap it down in the trailler but I guess it wasn't enough. Thanks

sometimes its just the vibrations or a few bumps alomg the way.if the picture is good and you have black on top and bottom of picture shrinking then its a vertical problem.if the picture is full screen and the red and blue seperate like 3d then its a convergence problem.ussully if you can tap around and make id do it it could be a loose solder connection good luck