I just acquired a 1967 Williams Shangri-La. The machine is in great condition and appears to work fully, as far as I can tell. The machine has not been hacked up or abused, and has been with the same owner for the last 50 years in a climate controlled room. This is my first pinball machine and I'm pretty good with a multi-meter, soldering, and general mechanical work. I did some light cleaning all around, replaced the usual rubber parts, lamps, and put in a new ball.
The machine is set to free play: When the front left red button is pushed, the machine turns on, resets, and starts a 2 player game. How do I undo this so that coins must be used? My only research indicates that the 'credit wheel' might be where free play was set. I don't want to break anything by guessing, so I'm seeking advice from people who are likely to know what to do.