Quoted from pinkid:I have a voltmeter, but I am not sure on what setting I should use,
Voltmeter set to DC volts, 50 is what you will be measuring so choose an appropriate range if your meter is not auto ranging.
Game on, start a game. one lead of your meter on the coil lug, the other on ground braid. Should be pretty close to 50v.
https://www.pinwiki.com/wiki/index.php/Williams_System_9_-_11#Flipper_problems