System 9 versus System 11 display data
System 9 uses 7-digit numeric displays only, sends BCD data with no ribbon cable to the display board, and the master display board decodes it. System 11 drives the alphanumeric segments directly from the CPU board over a 26-pin ribbon cable.
Systems
Related tips
- UDN display driver chips
- Characters missing from a display
- Display board chips shown as 4050 are really 4049
- Telling a shorted UDN chip from a shorted display glass
- Displays dead after the CPU board was removed
- Same segment missing across one 16-digit display
- High-voltage fuse blows once the display connector is plugged back in
- Same character position dead on every display: digit strobe wire at MPU J2
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell