Identify the power supply, MPU and sound board generation first
Bally and Stern games of 1977-1985 mix several generations of power supply, MPU and sound board, and the right test points, fuses and fixes depend on which ones the game has. Read the part number silk-screened on each board before starting.
Systems
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)