The dot matrix display is blank or unstable.

Display not working: check +5 V at the controller first

Cause: Low +5 V at the display controller, usually from resistance in the connector carrying it. Most common on the 192 x 64 display.

Checks

• Measure +5 V on the controller board itself, with the game running.

Fix

• Repin the +5 V connector so the controller sees a full 5 V.

Systems

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

Related tips

• Dot matrix controller boards and processors by game
• Dot matrix display goes blank after a few minutes
• The dot matrix display has its own computer
• Display shows "Command" numbers instead of animations
• Dot matrix controller CPUs by display size
• Dot matrix controller boards
• The three Data East dot matrix display sizes
• Voltages a small or medium dot matrix display needs

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