With LED bulbs in the flashers, some flashers flicker every time a flipper button is pressed.

LED flashers blink when the flipper buttons are pressed

Cause: From Big Guns on, the coil diodes moved onto the auxiliary power driver board and four circuits (solenoids 3A, 4A, 6A, 7A) run from the 50 V flipper supply. A little current leaks into them when the flippers fire, enough to light an LED.

Fix

• Fit diodes at those four coils and remove D3, D4, D6 and D7 from the auxiliary power driver board (see the modification procedure).

Systems

• Williams System 11A
• Williams System 11B
• Williams System 11C

Games

• Bad Cats
• Banzai Run
• Big Guns
• Black Knight 2000
• Bugs Bunny's Birthday Ball
• Cyclone
• Diner
• Dr. Dude And His Excellent Ray
• Elvira and the Party Monsters
• Jokerz!
• Mousin' Around!
• Police Force
• Pool Sharks
• Radical!
• Riverboat Gambler
• Rollergames
• Space Station
• Swords of Fury
• Taxi
• The Bally Game Show
• Transporter the Rescue

Related tips

• Whole A or C bank of coils dead
• C-bank coil or flasher not working
• Wrong coils fire together (A/C bank game)
• Whole groups of coils or all flashers dead: A/C select relay stuck
• Outhole, Spook House target reset and flashers all dead: blown fuse on the aux board
• How the System 11 A/C bank select works
• Later System 11 moved relay and diode boards to the backbox
• A-bank coil not working

Source: How to modify System 11b and c Auxiliary Power Driver Board to Eliminate some flashers from blinking when flippers are engaged using LED Flasher bulbs