Why EM switch contacts get dirty

Every time an EM switch opens or closes it arcs, most visibly on flipper and kicker circuits. The arc burns the contacts slightly, leaving black silver sulfide and pitting; the sulfide conducts but a heavy build-up and pits raise resistance until the switch fails.

Systems

• Electro-mechanical

Related tips

• File EM switch contacts
• Game stopped working after filing switches
• Cleaning leaf switch contacts
• A switch blade has lost its contact
• Replacement switch contacts for EM games
• Switch gap and adjustment targets
• Tighten a switch stack before adjusting it
• Adjust a leaf switch at the stack

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