Bring a repaired board set back into the game

Steps

• Fit the game ROM and flipper ROMs. Remove fuses F2 (solenoids) and F3 (lamp matrix).
• Power on and confirm the game boots.
• Power off, fit F3 and check that the attract mode lamps work.
• Power off, fit F2 and power on. If any coil locks on, switch off and look for a shorted coil driver transistor on the driver board.
• Passing Leon's and the built-in tests is a strong sign but not a guarantee the boards will work in the game.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Solenoid fuse blows at power-on: frayed 28 V wire touching ground under the playfield
• Pull the coil and lamp fuses for the first power-up
• Pull fuses F2 and F3 until the CPU board runs properly
• Pull F2 and F3 when first powering an unknown game
• Solenoid fuse blows: check the coin lockout coil
• CPU LEDs flash once, then come back on and stay on
• LEDs flicker then stay on: flipper or game ROM problem
• Free play won't take on System 7: do a factory reset first

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)