Leave the ROM jumpers alone until the LED flickers

Changing jumpers on a dead board can add a second fault to the first. To rule out U6 without touching the jumpers, swap in a proven ROM of matching type, or try the suspect chip in a working game.

Systems

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

Related tips

• Flicker but no first flash
• Get the MPU booting before you change any ROM jumpers
• Bally -35 MPU jumper settings by ROM type
• Bally -17 and Stern M-100 ROM jumper settings
• Stern M-200 MPU jumper settings by ROM set
• How to read Bally jumper charts and identify ROM types
• ROM types that share a jumper setting are not interchangeable between games
• Checking U6 and the jumpers with the U9 VMA line

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