I have Mitsubishi model WS-55809 55 in. projection

The problem is with the convergence circuit that is controlled by a couple fo convergence ICs. These are large black ICs attached to a heat sink and are marked STKxxx. Since a good whack seems to fix the problem, it suggests that the connections to the pins on these ICs has broken. This is a common failure adn is easily fixed. Please note that there are potentially dangerous high voltages present inside the set even when itis unplugged. If you can solder, resolder the pins on the ICs. That should resolve the problem. If not, then there is an internal bad connection within the ICs and they should be replaced. The parts cost is around $25-$25 per IC. There are 2 in this set.

Good luck,

Dan

has a problem on the cards are not making good contact is requested revicion cold welding technique