Eddy sensors: electronic ball switches under the playfield

From 1993 Williams used eddy sensors, solid-state switches that detect a steel ball passing above them, where a mechanical switch would not fit or would spoil the look. Star Trek Next Generation, Roadshow and Theatre of Magic use the adjustable type with a control board under the playfield; Twilight Zone uses an older, different design at the ball trough.

Systems

• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)

Games

• Red & Ted's Road Show
• Star Trek: The Next Generation
• Theatre of Magic
• Twilight Zone

Related tips

• Eddy sensor board R1 values by game
• Eddy board LED will not turn off at any pot setting
• Check opto power supply message with good fuses: reseat the opto board plug
• Cannon won't turn on the third multiball shot though it tests fine: flaky opto wire
• All playfield optos dead after replacing one opto: failed 16-opto board
• Opto still dead after replacing both sides: the new transmitter can be bad
• Turn ends while a ball is still in play in Final Frontier: flaky trough opto
• Gumball enter opto (switch 87) never registers: replace the LM339

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