After an incident where every playfield lamp lit and then went out one by one, almost all controlled lamps stay dark or flicker when solenoids fire, even with replacement MPU and driver boards.

Most controlled lamps dead or flickering with the solenoids: loose bulb sockets

Cause: The controlled lamp sockets had lost their grip on the bulbs, so the contacts were intermittent.

Checks

• Test a dark bulb in a known good socket; these games can put full lamp voltage on bulbs if the lamp circuit locks on, which kills incandescents and LEDs.
• Measure the voltage reaching the sockets.

Fix

• Pull each bulb, bend the socket tabs in so they grip, and refit the bulb; replace bulbs that test bad.

Systems

• Williams System 4

Games

• Phoenix

Related tips

• A single lamp does not light
• How the lamp matrix runs 6.3 V bulbs on 18 V
• No lamp matrix voltage
• Some lamp columns over-bright: board or playfield?
• Diode-test the lamp pre-drivers (2N6427/MPSA14)
• Lamp rows stuck on: the 7406 at IC19
• Photo: MOSFET lamp drivers with jumper wires

Source: Pinball Repair help group!! (Facebook group)