Segments stay missing with a good power supply and good 4050s.

Alphanumeric segments still missing: the UDN chips

Cause: One of the four UDN7180 segment drivers (most often) or four UDN6118 strobe drivers on the display controller.

Checks

• Both chips have inputs on pins 1 to 8 and outputs on pins 11 to 18; compare inputs and outputs with a logic probe, using the schematic to find which chip serves which display.

Fix

• Replace the failed chip.

Systems

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

Related tips

• High-voltage display fuse F3 keeps blowing
• One six-digit display completely dead
• Using a Taxi/Police Force display board in another 16-digit game
• Combining two 27020 display images into one 27040
• Alphanumeric power supply CN5 pinout
• Checkpoint: CPU and display EPROM types and latest versions
• Teenage Mutant Ninja Turtles: CPU and display EPROM types and latest versions
• Batman: CPU and display EPROM types and latest versions

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