All the switched coils work, but five of the switched (C side) flashers don't light; instead an upper flasher lights each time one of them is fired. New resistors, diodes and even an MPU swap made no difference.

Switched flashers fail and another flasher lights instead: bent tall socket shorting

Cause: Someone had fitted a tall flasher socket where a short one belongs and bent it back on itself to get the height. With a bulb in, it shorted against the neighbouring wiring; with the bulb out the circuit looked normal.

Checks

• Inspect every flasher socket on the affected circuits with the bulbs fitted, especially in tight spots such as beside the left ramp.
• Look for non-original sockets and bent socket brackets.

Fix

• Replace the bent tall socket with the correct short socket.

Systems

• Williams System 11A

Games

• Pinbot

Related tips

• C-bank coil or flasher not working
• What a bad coil diode does

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