Quick checklist for an EM game that won't play

Steps

Switch the game off and confirm the wall outlet actually works.
With a meter on AC volts, confirm about 115 V reaches the input (primary) side of the transformer; cords 30+ years old often have broken conductors.
Test every fuse with the meter, and the fuse clips as well (Bally fuse holders are the usual offenders).
Make sure the coin door cable is connected (essential on Gottlieb).
Put credits on the credit wheel by hand, or set the game to free play.
Check that no coin door switch is stuck shut.
Optionally turn the player 1 score reels off zero by hand, so you can see whether the game can zero them; if reels cannot reach zero the game never finishes its reset.
Check the power switch, if the game has one, then switch on. On many 1970s Bally and Williams games the lights come on only after the left flipper button is pressed.
Press the coin door start button and follow the entries for the symptom you see (no start, motor runs on, fuse blows, features not resetting).

Unplug the game first: the power cord, fuse block and transformer primary carry 115 V line voltage.

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