Resets or lock-ups, with +5 V test points reading low or unequal.

Resets from a burned SDB J3 pin 12 (12 V feed for the +5 V)

Cause: All of the game's +5 V comes from one orange 12 V wire on SDB J3 pin 12 through a single .100" pin, which often burns or goes intermittent.

Checks

• Measure SDB TP5 (top, 12-14 V DC unregulated), then TP1 and TP3 (4.95-5.25 V DC). Any difference between TP1 and TP3 points to J3 connector trouble.

Fix

• Replace the J3 housing pins and the board's .100" header pins. If J3 is an IDC connector, replace the whole 25-pin housing with a crimp-pin type.
• A wire soldered between TP1 and TP3 relieves the connector. Double-check you have the 5 V points: tying TP5 (12 V) to them destroys MPU chips.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Globetrotters reboots during play (GI stays on)
• No +5V on any board and no MPU LED: bad return pin in the solenoid driver board J3 plug
• Rectifier test point reads below its range
• Burnt rectifier J3 pins 8 and 17
• MPU won't boot and driver board test points read low: replace the solenoid driver board
• Solenoid select lines: MPU PIA U11 to SDB 74154 pin map
• What each rectifier on the board feeds
• Controlled lamps dim and TP1 reads about 2.8 V instead of 5.4 V: half the bridge open

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