Neither flashlamp on a driver flashes, though they may glow faintly.

Flashlamps never flash

Cause: The low-value fire-path resistor (1 ohm, on some games 5 ohm, rated 1/2 W) is open.

Checks

• Measure the small resistor on the flasher resistor board.

Fix

• Replace it.

Systems

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

Related tips

• Two flashlamps out together
• Check for power at a coil or flashlamp
• Fire a coil or flashlamp by grounding it
• Check the wire from the coil to its driver transistor

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