Some segments fail on certain characters only, such as the top of a 0 or 7.

Parts of some characters missing on alphanumeric displays

Cause: A failed 4050 (14050) CMOS input buffer on the display controller; these are static sensitive.

Checks

• With power off, measure from ground to each input and output pin of the 4050s (the guide lists them at U6-U8, U1 and U5 on the display controller); a pin that reads differently from the rest is suspect.
• With an analog meter, look for a pin that does not kick the needle like the others.

Fix

• Replace the faulty 4050.

Systems

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

Related tips

• No sound in play or solenoid test, and grounding inputs does nothing
• Check the segment resistors before buying a UDN7180
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Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)