The game boots, reaches attract mode and starts a game, but resets after some flipper action.

Game resets when the flippers are used: recap supply and renew MPU power connector

Cause: The logic supply dips for an instant when the flippers pull in. Usual causes are an aged power supply filter capacitor (the large 18,000 uF cap), other tired caps, or a worn power connector between the supply and the MPU. Flipper coil diodes are also worth checking.

Checks

• Check the flipper coil diodes are intact and the right way round.
• Run a clip lead from the 5 V test point on the power supply to the 5 V test point on the MPU and play. If the resets stop, the connector or wiring between them is suspect; if they continue, suspect the supply filter cap.
• A meter will not catch a brief dip; use a scope if one is available.

Fix

• Recap the power supply, including the large 18,000 uF filter cap, and recap the MPU.
• Replace both the male header and the female housing and pins of the MPU power connector.

Work on the power supply with the game unplugged; large filter caps can hold a charge.

Systems

• Williams System 11

Games

• High Speed

Related tips

• Resets continue after diode repair: power and connector checks
• Right-side playfield GI out: a wire not seated in a new power board connector
• Occasional U10 PIA error at power-on, but the game plays
• "IRQ Failure" at power-on
• Pop bumper, sling and right-side GI lamps all go out at once: blown GI fuse
• Half the backbox lamps and the lower displays dead: check the backbox fuses
• What the System 11 power supply board feeds
• Power supply board fuses (typical game)

Source: Pinball Repair help group!! (Facebook group)