Check the segment resistors before buying a UDN7180
Trace the missing segment through its UDN7180 to its resistor and check it is within 10% of the schematic value, along with its solder joint. Without a schematic, check every resistor on the master display board; the larger 1/2 W ones fail more.
Systems
Related tips
- Testing UDN6118/UDN7180 chips for shorts
- UDN6118/UDN7180 pinout and what each failure looks like
- Same segment missing across one 16-digit display
- Segment missing or stuck only on certain characters
- One segment lit on many characters of the top display: unsoldered leg on a driver chip
- High-voltage fuse blows once the display connector is plugged back in
- System 9 versus System 11 display data
- Display board chips shown as 4050 are really 4049
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell