Mach doch mal folgende Tests (ich hoffe, du bist dem Englischen einigermaßen mächtig; Quelle: pinwiki.com):
Testing the complete MPU switch matrix circuitry requires a jumper wire with a conductor on each end (or at least bare wires). This test will verify both the column and row circuitry on the MPU.
Remove CN8 and CN10 from the MPU.
Power the game on.
Place the game in switch test.
Using a short length of wire with a clip on at least one end, jumper pin 1 to pin 1, then pin 2 to pin 1, etc.
Each time you jumper a pin, a single switch closure should be reported.
If the game reports only a single switch closure each time you jumper two pins, your MPU is working fine.
If the game reports multiple switch closures when you jumper two pins, then your MPU switch matrix has been damaged, probably by shorting high voltage to either a switch matrix row or column on the playfield. Reminder...never risk shorting high voltage to the switch matrix by working on the game with power on.
Testing the complete MPU switch matrix circuitry requires a jumper wire with a conductor on each end (or at least bare wires). This test will verify both the column and row circuitry on the MPU.
Remove CN8 and CN10 from the MPU.
Power the game on.
Place the game in switch test.
Using a short length of wire with a clip on at least one end, jumper pin 1 to pin 1, then pin 2 to pin 1, etc.
Each time you jumper a pin, a single switch closure should be reported.
If the game reports only a single switch closure each time you jumper two pins, your MPU is working fine.
If the game reports multiple switch closures when you jumper two pins, then your MPU switch matrix has been damaged, probably by shorting high voltage to either a switch matrix row or column on the playfield. Reminder...never risk shorting high voltage to the switch matrix by working on the game with power on.