Mitsubishi vs-60607 60" screen is

When picture is getting smaller in size or goes away or moves towards one side then hit your TV lightly on left side or right side or on top & then observe ..........you will get normal picture or it comes & again it goes....if it is happening like that then following is the situation..........after 4 or 5 yrs in some TVs on main board at some soldering joints crack develops....then due to loose contact picture becomes small in size or disappears ...........when we hit that lightly then those loose contacts joins temporarly & again picture appears for some time............so solution is ......TV main board should be observed carefully & most of the joints should be re-soldered.......only a good service engineer can do that........even after hitting TV lightly if there is no response then main board has to be checked completely........in your case iam sure it is loose connection problem.........joints should be re - soldered ...100% it works again................this problem cannot be solved by user unless user has idea about components( resisitors, transisitors, diodes,...etc) , have soldering iron , multimeter & other tools....................so contact good TV service engineer