Fit a replacement switch diode the right way round

Steps

• Use a 1N4004 (a 1N4001 or 1N4002 also works).
• Match the band to the old diode, but compare with a working switch nearby, since the old one may have been wrong.
• Usual wiring: green ground wire on the centre lug, white row wire on the lug next to it, diode band alone on the far (common) lug, and the plain diode end on the same lug as the row wire.
• Leaf switches follow the same pattern. The game manual notes any switch wired differently.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Fitting a new switch diode the right way round
• Test the switch column drivers with a diode jumper
• Test the switch row inputs with a diode jumper
• Switch row (return) circuit on the CPU board
• False switch readings only when several switches are closed
• Testing a switch diode out of circuit
• System 80 switch matrix diodes
• Spare diodes for coils and switches

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)