After switching on, a kicker or eject coil pulses repeatedly; the dot matrix may be blank, show one line or garbage.

A coil keeps firing at power-on and the DMD is blank

Cause: The unregulated 12 V fuse that powers the opto LEDs has blown (F116 on WPC-S and earlier, via BR5; F109 on WPC-95). With the opto emitters dark, the game thinks a ball is sitting in an eject and keeps kicking. Some displays also need this 12 V.

Checks

• Check F116 (or F109 on WPC-95) out of its holder.
• On WPC-S and earlier, test BR5 if the fuse blows again.

Fix

• Replace the fuse; if it blows again, look for a shorted 12 V device such as a motor or opto board.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• F112 then F103 blow after a socket shorted a switch: isolate to the supercharger board
• F111, F112 or the line fuse keeps blowing
• Switch matrix fuse F115 (F101 on WPC-95) blows as soon as it is replaced
• "Check Fuse F114/F115" (F106/F101 on WPC-95): step-by-step
• Cannons and a flipper lose power at once: a fuse that looked fine was blown
• F103 blows instantly: shorted ramp diverter coil; magnet fires the diverter if F104 open
• DMD dark and F116 keeps blowing: battlefield switches making the pusher run wild
• WPC power driver board fuses and what they feed

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)