Testing an under-playfield relay board

Steps

• With the game on (coin door closed on WWF Royal Rumble and later), clip a jumper to the ground strap by the prop rod.
• Touch the other end to the relay board's DRV lead (on the Jurassic Park board pictured, the blue wire second from the bottom).
• The relay should click and its device run; on a GI relay the connected playfield lamp string goes out.

Systems

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

Related tips

• Low coil voltage from pitted L/R relay contacts
• Testing the L/R select relay by grounding Q29
• The solenoid L/R select relay and transistor Q29
• Bank select relay and CPU transistor Q29
• Ball return kicker keeps firing every few seconds: switch bent closed
• L/R relay never clicks: test Q29
• All L or all R bank coils/flashers dead: PPB relay K1
• L/R relay burnt or intermittent

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