All or part of a display is extremely bright and garbled.

Display very bright and scrambled

Cause: Faulty display driver board.

Fix

• Switch the game off as soon as possible and have the driver board repaired.

The display supply runs at about +100 V and -100 V; switch off before touching the display or its driver board.

Systems

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

Related tips

• Check every segment with the display test
• System 11 alphanumeric displays
• System 9 versus System 11 display data
• UDN display driver chips
• Score display layouts across System 11
• Lower the display voltage to 91 V to extend display life
• Characters missing from a display
• Spare UDN7180 at U12 on Pinbot display boards

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer