Stepper cleaning, part 1: mark, check and remove the wipers

Steps

• Switch the game off.
• On two-coil steppers, set the unit to its reset position (or leave it where it is if seized) and mark one wiper finger and the edge of the bakelite board beside its rivet with a marker, so it cannot go back 180 degrees out.
• Before taking anything apart, check the fingers sit centred on their rivets; if they fall between rivets the bakelite plate has shifted, so rotate it back and tighten its screws.
• Remove the wiper disc: on Bally take out the Phillips screw while holding the nylon cog; on Williams undo the 7/16" nut while a screwdriver in a cog hole stops it turning; on Gottlieb usually two or three slotted screws.
• Gottlieb player units can often be cleaned without removing the wiper disc.

Systems

• Electro-mechanical

Related tips

• Stepper cleaning, part 3: rivets, wipers and lube
• Stepper cleaning, part 4: refit and test
• Cleaning and aligning an EM stepper unit
• Set stepper wiper finger tension and alignment
• Repair a broken or worn stepper wiper arm
• What stepper units do in an EM
• Burnt pad on a stepper unit's contact board
• Kinds of stepper unit

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part One, Clay Harrell (pinrepair.com)