Resets, dead logic or browned pins at rectifier connector J3.

Burnt rectifier J3 pins 8 and 17

Cause: J3 pin 8 (orange, the 12 V DC feed for the +5 V regulator) and pin 17 (white/brown ground) carry heavy current to the solenoid driver board and overheat.

Checks

• Inspect both pins and the housing for any browning.

Fix

• Replace header pins and housing pins on both, using Trifurcon pins.

Systems

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

Related tips

• Replace browned rectifier header pins and housing pins together
• Pre-Xenon rectifier board outputs by connector
• Rectifier board J3 pin functions (pre-Xenon backbox transformer)
• AS2518-18/-49 connector functions
• Pre-Xenon transformer to rectifier board wiring
• Early Bally SS rectifier board: worn ground mounting pad and cracked header pins
• Burnt pins at solenoid driver J3
• Only the GI lights and the MPU won't boot: bad connection at J3

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