Something stops working on an EM game with no obvious cause.

EM feature dead: dirty interconnect plug

Cause: Dirty or corroded male pins on the large plugs linking playfield, cabinet and backbox (up to about 20 wires each).

Checks

• Unplug each connector and look at the pins.

Fix

• Scrub the pins bright with fine sandpaper, crocus cloth, steel wool or a fine wire brush, then reconnect.

Systems

• Electro-mechanical

Related tips

• Match lights work but a match gives no credit: dirty Jones plug in the match path
• Old bakelite plugs crack easily

Source: Pinball Machine Care & Maintenance, Bernard B. Kamoroff (Bell Springs Pinball Alley)