Talk:Gameplan Repair

A reliable workbench test of an MPU-2 is possible.

Full boot of an MPU-2 on workbench with a standard PC power supply and only one further voltage supply is simple and valid. Only three voltages are used: +5 volt and +12 are from the PC power supply. And a third DC voltage from +12 to +24 volt. Because this third voltage is used to generate the logic zero cross detection this voltage must be generated by a bridge rectifier and a resistor (5 watt 700 ohm on the gameplan power supply but also 200 up to 1000 ohm are working) between plus and minus. The resistor ensures the zero crossing is reached stably. Connect the ground from the third source to the ground of the power supply! So this should always results in 6 flashes while booting.

On connector J1 Pin 14 and 15 are 0 volt = ground Pin 13 is +12 volt Pin 11 and 12 are +5 volt Pin 3 +12 up to +24 volt not from PC power supply

Use a logic probe on J4 Pin 2 to check that after the 6 flashes this output send a signal to the soundboard. Next step is a short connection between J6 Pin 3 and one of J6 Pin 6 or 7 or 8 to simulate a credit coin. Again the logic probe on J4 Pin 2 should send signals to the soundboard. Start a game with a short connection between J6 Pin 1 and J6 Pin 3. And again the logic probe on J4 Pin 2 should send signals to the soundboard.