In flasher test, firing one playfield flasher also lights all of the saucer flashers. It only happens with the backbox lamp insert board connected.

One flasher fires all the saucer flashers: backbox flasher feed on the wrong header

Cause: The small connector that feeds flasher power to the backbox insert board (a single red/white wire) was plugged into one of the identical, keyed spare headers on the driver board instead of its own header, J134.

Checks

• Look for an empty J134 on the driver board and a stray connector with a single red/white wire on one of the other similar headers.
• If the connectors are right, follow wire colours on the insert board for two flasher circuits tied together. The backbox flasher sockets have no diodes; that is normal.

Fix

• Move the connector onto J134.

Systems

• WPC-95

Games

• Attack from Mars

Related tips

• One flasher never lights
• Flasher glows full bright until the bulb blows: shorted driver transistor
• Two or more coils fire together
• One coil will not fire
• Firing each coil from the WPC solenoid test
• A solenoid will not fire in the solenoid test
• A flasher stays on or is very bright
• A coil does nothing although its fuse is good

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