PS42B451 Missing Right Side of Picture.

Was given a 2nd hand PS42B451B2XXXU as it isn't working correctly, the picture is missing about 3 Inches on the right hand side of the screen top to bottom, strange thing is the picture test says the unit is a PS50B430 !! anyone think this could be the problem, have read threads about changing the model number to access additional features ? Apart from that any ideas ? Thanks NB