A display shows wrong, missing or stuck segments or digits.
Telling a bad display driver from a bad display tube
Cause: A failed UDN6118 driver chip or a failed Futaba tube.
Checks
- A high input on a driver chip should give a high on the matching output.
- If an output is on all the time or never follows its input, the driver chip is bad.
- If the driver outputs are right but wrong segments light, the tube is shorted inside.
- If the driver outputs are right but segments never light, the tube is bad.
Fix
- Replace the driver chip or the display tube as indicated.
The display supply carries 60 V DC (and 42 V DC); keep fingers off the power supply and display boards while the game is on.
Systems
Related tips
- A display segment or digit is always on or always off
- Replacing a display glass tube
- Meter checks on a display tube
- Meter check of the UDN6118 display drivers
- Seven-digit display board (A14) parts
- Score displays are off but the status display works
- The display voltages to check
- How the Gottlieb fluorescent displays work
Source: System 80 Service Manual, Gottlieb