Score displays flicker or behave oddly on a game with a backbox auxiliary (marquee chaser) lamp board, such as Haunted House, Black Hole, Volcano or Mars God of War.

Displays flicker on games with an auxiliary lamp board

Cause: Unreliable ground to the auxiliary lamp board.

Fix

• Find the wide trace running from near the lower-left chip toward the edge row of MPS-U45s and scrape its mask.
• Solder a wire there and run it to the power supply frame.

Systems

• Gottlieb System 80

Games

• Black Hole
• Haunted House
• Mars God of War
• Volcano

Related tips

• Backbox chase lights run from their own board
• Backbox chase lights not running
• Displays flicker in time with the backglass light show
• Coils pulse briefly at switch-on on Volcano, Black Hole and Haunted House
• Black Hole and Haunted House third relay ("U")
• Haunted House and Black Hole fuse panel
• Correct up-kicker coil for Black Hole and Haunted House
• Haunted House and Black Hole sound board DIP switches

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)