Mitsubishi HD 1080 series - no picture with certain inputs

we have a mitsubishi HD 1080 series rear projection tv made in fall of 2000. the DVD player thru component video works fine on either 1 of 2 component connections. Every other connected device including games, cable tv, and Roku (thru component or red white sound yellow video) work intermitently, then screen goes blank with about an inch of screen visible at top only. struggling with what to do - I opened back, no obvious loose connections. Ideas? I certainly would appreciate specific direction to a fix that saves me from bringing the huge tv into the repair shop - is there an adjustment to make? is there a likely component or board that is at fault here? Thanks