Work every System 1 game needs
Plan on: a larger 6800-10,000 mfd C1 filter cap in the power supply; ground wires from the power supply, CPU and driver boards to the backbox frame; removing the original CPU battery for a remote AA pack with a 1N4004 blocking diode; cleaning any battery corrosion; and re-pinning the board connectors, certainly CPU J5, J6 and J7 and likely driver J1.
Systems
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Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)