The ball release coil stays energized after the first point is scored, and the switches on the ball release coil and the one-point relay throw big sparks.

Ball release hold coil won't release, big spark on its switches

Cause: This coil is a hold type; a normally closed contact on the one-point relay is what drops it out. Overheating has shorted its turns, lowering its resistance, and the heavy current arcs across the switch so it never truly opens.

Checks

• Measure the ball release coil. A healthy hold coil reads roughly 12 to 200 ohms; under about 10 ohms it overheats quickly.

Fix

• Replace the coil; the arcing then stops and it releases normally.

Systems

• Electro-mechanical

Related tips

• A switch throws a big blue spark
• Williams 1950s coil numbers drop the first dash
• Game resets but no playfield solenoid works
• Gottlieb pop bumper relay and score reel stuck on
• Pop bumper stays on after the ball hits it

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