One flasher or group of flashers does not work.

Flashers dead on Banzai Run and later: interconnect board resistors

Cause: The flash lamp resistors on the interconnect board run hot enough to desolder themselves, or break from vibration. Their value (4, 5, 7 or 10 ohm) is set by how many bulbs share one driver.

Checks

• Inspect each flash resistor on the interconnect board for cracked joints or breaks; measure it against its marked value.

Fix

• Resolder or replace the resistor with one of the same value and wattage.

Systems

• Williams System 11B
• Williams System 11C

Related tips

• Double flasher circuits barely light: new interconnect board has 5.6K resistors
• The interconnect board (Banzai Run and later)
• One topper dome flasher pair dead while its shared knocker works: broken wire
• GI out on Banzai Run and later: burnt interconnect connector 2J6
• Right flipper dead after a coil cooked: burnt trace on the interconnect board
• Interconnect board and flipper power board fuses
• Interconnect board from another game fitted: the values Jokerz needs
• Roulette wheel not working: worn J15 connector on the interconnect board

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)