After the first switch scores, the 100s keep counting up on their own, though no switch is stuck and the Z9/Z28 inverters test good.

Buck Rogers keeps adding 100s by itself

Cause: A bad or dirty game PROM.

Checks

• Rule out stuck switches with a logic probe on the matrix inputs.

Fix

• Try a known good PROM; cleaning the legs of the original and reseating it also cured it.

Systems

• Gottlieb System 1

Games

• Buck Rogers

Related tips

• Buck Rogers: game PROM letter
• Joker Poker: game PROM letter
• Dragon: game PROM letter
• Charlie's Angels: game PROM letter
• Solar Ride: game PROM letter
• Pinball Pool: game PROM letter
• The Incredible Hulk: game PROM letter
• Genie: game PROM letter

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)