The Stern M-200 MPU board set has one major issue that the collector is advised to deal with as soon as possible. The NI-CAD rechargeable battery (shown in this picture at the red arrow) should be removed and a different system installed. See Marvin's guide on Bally/Stern to view an illustration of how this is done.
A radio shack 4 AA battery holder is used (using 3 batteries and a blocking diode in the 4th slot) after the old rechargeable is removed. The diode is necessary to prevent the system from trying to recharge your new alkaline batteries (if you do not do this it could cause damage to the boards and possible injury to yourself). Then the new battery cage is connected by wires and located off of the board somewhere in the backbox to avoid battery leakage on the valuable boards. See picture left. Wires are attached where the NI-CAD use to be. These are connected to the new battery cage.
Please note: This game will function without any battery attached to it. The battery is to save the high score and credit number. All other settings such as number of balls per game and how many credits per quarter, etc, and controlled by the 4 banks of dip switches (shown in the first picture with the orange arrow)
The under playfield workings. At the time that this picture was taken I had not yet cleaned up and replaced lights and coil sleeves. It's a bit dirty. I am impressed by the workmanship in these old Stern games. The large plates on the bottom contain the well designed drop target mechanisms. Most of the lights are mounted on long strips of metal and grounded together. The pop bumper is very easy to service. The whole unit can be pulled with just a few screws.
