On a 1975-78 Gottlieb 4-player, both player 1 and player 4 light on the backglass after start.

Gottlieb 4-player shows players 1 and 4 lit at start

Cause: The coin unit beside the chime box isn't stepping up from zero to the one-player position.

Checks

• Watch the coin unit as start is pressed; it should step down to zero then up one.

Fix

• Clean and adjust the coin unit and its step-up coil switches.

Systems

• Electro-mechanical

Related tips

• 1975+ Gottlieb won't reset: Ax/Bx latch relay blades out of their slots
• Gottlieb player unit
• Gottlieb coin unit (1975 to 1979)
• Gottlieb Ax/Bx/Dx relays, coin unit and player unit: what each does
• Gottlieb 1970s Ax/Bx latch-trip relays misbehave
• Two-player game runs on to players 3 and 4: hidden broken wire on the coin unit
• Game starts but flippers are dead and nothing scores: dirty relay switches
• Gottlieb reset bank solenoid and S start relay run on 120 V

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