Pressing start does nothing and the score motor never turns.

Score motor doesn't move to its next home position

Cause: No coil voltage (30 or 50 V) because of a blown fuse or a bad fuse holder, or a pitted or misadjusted score motor home switch.

Checks

• Lift the playfield and turn the score motor slightly by hand with the game on.
• It should carry on by itself to the next home position: every 120 degrees on Gottlieb, every 180 degrees on Bally and Williams.
• If it doesn't, check the coil-voltage fuse and its holder, then the home switch.

Fix

• Replace the fuse or re-tension or replace the holder.
• Clean, file and gap the home switch.

Systems

• Electro-mechanical

Related tips

• Players 3 and 4 reset but players 1 and 2 never do at game start
• Score motor runs on and the game never starts
• Score motor overruns or freezes: worn home switch
• Why the score motor home switch arcs on opening only
• What the score motor does
• 1970s Chicago Coin: motor runs on at reset
• Ball not kicked out of the outhole at game start: score motor 1D switch
• How the score motor resets the reels

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)