Why the MPU has ROM jumpers

The jumpers tell the MPU what type and size of ROMs are fitted and how many, so one board can run any game with masked ROMs or EPROMs. If they do not match the ROMs installed, the board cannot run the ROM code that turns the LED off, and the LED stays locked on.

Systems

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

Related tips

• Get the MPU booting before you change any ROM jumpers
• Get the MPU working before changing jumpers
• Bally -35 MPU jumper settings by ROM type
• Stern M-200 MPU jumper settings by ROM set
• 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 Two, Clay Harrell (pinrepair.com)