In display test one segment is missing across the whole lower (or upper) 16-character display, while the other display shows it.

Same segment missing across one 16-digit display

Cause: One failed leg of a UDN7180 segment driver on the display controller board. On pre-Taxi games one chip can take out the segment on both lower displays.

Fix

• Find the UDN7180 for that segment from the schematic, socket it and replace it.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• UDN display driver chips
• UDN display driver chips
• Segment missing or stuck only on certain characters
• One segment lit on many characters of the top display: unsoldered leg on a driver chip
• System 9 versus System 11 display data
• Check the segment resistors before buying a UDN7180
• Telling a shorted UDN chip from a shorted display glass
• Displays dead after the CPU board was removed

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell