A single display is blank.

One score display dead

Cause: Usually the display glass itself, which wears out. A glass can also short internally, killing UDN driver chips and blowing F1.

Checks

• Swap display cables if possible to see whether the fault follows the glass.

Fix

• Replace the glass first when a display is completely dead.

The display supply carries about 100 V DC (plus and minus); keep fingers and probes off the master display board and power supply high-voltage section with the game on.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• All score displays dead
• Score displays dead but digits glow: bad wire in the CPU blanking plug (1J3)
• A segment missing on a score display
• Master display board versions
• Which UDN6184 drives which display
• Using a logic probe on the display board safely
• Four digits missing on the player 2 and 3 displays: bad driver IC12 on the master display
• Test MPS-A42 and MPS-A92 display transistors

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)