Coils are weak; at the coil you measure under 50 V (50 V coils) or under 25 V (25 V coils).

Low coil voltage from pitted L/R relay contacts

Cause: Pitted contacts or cold joints at the L/R select relay add resistance in the coil supply.

Checks

• Remember unloaded readings run high: about 70 V on the 50 V supply and up to about 38 V on the 25 V supply are normal.
• Inspect the relay contacts and solder joints.

Fix

• Take off the relay cover if it comes off and lightly file the contacts.
• Reflow the relay solder joints.
• Replace the relay if it is burnt (24 V DC coil).

Keep hands off coil lugs and the solenoid supply while the game is on; 50 V coil circuits read up to about 80 V unloaded.

Systems

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

Related tips

• Under-playfield relay boards and the PPB board
• No voltage at either lug of a coil
• A low resistance coil means checking its driver chain too
• All L or all R bank coils/flashers dead: PPB relay K1
• 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
• Only flash lamps work when a game starts (L/R reversed games)

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