CPU does not run; U9 pin 2 is low.

U9 pin 2 (halt) is not high

Cause: Halt line pull-up resistor R135 broken or missing, or a short on connector J5.

Checks

• Check U9 pin 2 for +5 V.
• Check R135 and look for a short on the J5 pins.

Fix

• Replace R135 or clear the J5 short.

Systems

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

Related tips

• Test EPROM: the least an MPU needs to run it
• Tell a -35/-133 MPU from a -17 by counting J5 pins
• Run Freedom or Night Rider on a -17 with 2716s at U1 and U6
• Resetting replay values and high scores
• Power and ground pins of the main MPU chips
• -17 and M-100 boards cannot run 1979-1985 games without modification
• Make a stacked-socket adapter to run two 2716s on a stock -17 board
• M-200 with all 32 DIP switches off runs a built-in self test

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