Strengthening pop bumpers by removing coil windings

Steps

• Unwrap and keep the coil's paper wrapper (the coil can usually stay in the game).
• Cut only the outer winding wire at its lug; the inner end can't be unwound.
• Unwind three layers (roughly 40 turns per layer, removing 10 to 20 percent of the wire at most).
• Leave about two inches of wire, cut off the rest, and sand the enamel off that tail.
• Thread it through the original lug hole, wrap the remainder round the lug and solder.
• Refit the wrapper with a short piece of electrical tape and measure: never let the coil drop below 2 ohms.

Never do this to flipper coils. Stronger slingshots make short-flipper games much harder to control, so start with the pop bumpers.

Systems

• Electro-mechanical

Related tips

• How an EM pop bumper works
• Renew sleeves on flipper, pop bumper and sling coils
• Rebuilding an EM pop bumper
• Converting an EM flipper or bumper coil to DC
• Game resets but no playfield solenoid works
• Pop bumper armature links: which to use and how they go together
• Making pop bumpers kick harder
• Gottlieb EM coil windings, resistance and wrapper colour

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