Get the MPU working before changing jumpers

Jumpers that do not match the fitted ROMs leave the LED locked on, so a board that is not yet working should be repaired with its current ROMs and jumpers first. Only re-jumper once it boots.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Why the MPU has ROM jumpers
• Add a ground jumper on every -17/-35 MPU
• Get the MPU booting before you change any ROM jumpers
• Jumpers for a -35/-133 MPU running two 2732 EPROMs (U2 and U6)
• Bally -35 MPU jumper settings by ROM type
• Stern M-200 MPU jumper settings by ROM set
• Testing an MPU in the game with only J4 connected
• MPU board test points

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Two, Clay Harrell (pinrepair.com)