Service bulletin 75 explains the blanking circuit

If you are chasing a blanking fault, Sega service bulletin 75 describes how the CPU board blanking circuit works.

Systems

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

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