yup, david is right.
the zero switch in front of the spiral cam is one of two switches in series. The orange/black wire goes off the hopper to the reel mech where it goes to:
- reel mech B-1 switch, which is used to make a pulse to reset the win meter
- reel mech B-3 switch, makes a pulse onto the black/white 85-1 wire that goes back to the payout counter reset coil on the hopper
you need a pulse generated by a brief switch closure so the reset coils aren't held powered. Unless the machine has a motor with cams, the only place to get momentary switch closures every spin are switches getting moved by the mechanical parts of the reel spin mechanism after the reel kick.
even the handle is no good since people can partially pull or hold it down. Gets kinda expensive if the player could burn up coils whenever they lost :-)