Get the MPU booting before you change any ROM jumpers

If the ROM jumpers do not match the chips fitted, the MPU diagnostic LED stays lit and the board never starts. Only move jumpers on a board you already know works, so a wrong setting is the only thing that can be at fault.

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
• Bally -35 MPU jumper settings by ROM type
• Stern M-200 MPU jumper settings by ROM set
• Get the MPU working before changing jumpers
• Add a ground jumper on every -17/-35 MPU
• ROM and EPROM types used on Bally MPUs
• Jumpers for a -35/-133 MPU running two 2732 EPROMs (U2 and U6)
• Bally -17 and Stern M-100 ROM jumper settings

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