Display board chips shown as 4050 are really 4049
Some System 11 schematics label U8, U9 and U10 on the display controller board as 4050 non-inverting buffers. They are 4049 hex inverting buffers; fitting a 4050 can cause damage and leave the displays dead.
Systems
Related tips
- Segment missing or stuck only on certain characters
- Switch matrix connector pins and their chips
- UDN display driver chips
- Telling a shorted UDN chip from a shorted display glass
- A ball resting on one switch stops others in its column
- System 9 versus System 11 display data
- Testing UDN6118/UDN7180 chips for shorts
- Characters missing from a display
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell