In the bottom of the cabinet is the transformer. It is configurable for several common input voltages used in different parts of the world. On the front (toward the coin door) side of the transformer box there is a screw-in fuse holder for the line fuse:
Unscrew the knob and pull the fuse out. The knob part has a pin that can be turned to mate with the required input voltage when it is screwed back in to its recepticle.
It appears that to save money, that this option was removed from the last few games that they made. The adjustable transformer last appeared on Zankor. Spooky, Stars Phoenix, and New Stars Phoenix came with a 220V only transformer, with no adjustment selector, and not even a 110V tap. To run these games in the US, a 110VAC to 220VAC step-up transformer must be used, or the transformer out of a parted out game could be substituted.
Mystic Star is a Bally conversion, and uses the Bally board set and transformer.