Thanks for the information. The unit has a few issues such as;
1. The payout counter wheel doesn't reset all the time on the coin hopper assy. Therefore when I reset it manually it pays out correctly for the first win. And seems to deduct what it has already paid on subsequent wins.
the payout counter reset coil is controlled by two switches. The usual problem is the zero switch that is on the front of the payout counter mounted on the outboard carriage in front of the spiral. The switch needs to close when the unit is not reset, and only be open when the unit is reset. Its purpose is to prevent pulsing the reset coil when it's not needed.
you can quick check by using a jumper wire to connect the black/white 85-1 and orange/black 78-1 wires on the switch blades together and see if the counter resets then.
if it's not that, it could be the reel mech B switch (left side of reel mech, horizontal switches with 78-1 and yellow 30 wires.
if not that, its either plug connections, a broken wire or the coil itself.
2. The lights on the top assy for the third coin do not light up. The third coin light on the reel glass does. This row of lights never light up even when the unit is initially turned on. It did when I first got the unit from a friend to fix. It seemed to stop working after I cleaned the contacts on the step up wheel in the top assy.
the stepper turns on both the reel glass 3rd coin light and the top insert lights, so it's not the stepper.
the difference is the top insert lights also go thru switches on the top, center and bottom jackpot relays, so it should be one of those switches is open when is should be closed. See the 831-D schematic around K7 for the circuit going to the "3rd coin bally" lamp for the wire colors (38-3, 40-3 and 41-3) on the switches.
the idea is if you get one of the top jackpots, the game turns off the non-winning rows and flashes the winning row. The flashing uses a 455 flasher lamp to control a 6V relay. 455 lamps I think are no longer produced, so eventually the supply will run out and something else will be needed to make things flash.
3. The coin kicker relay buzzes sometimes pretty loudly and I have to open the door and move the paddle in the door to get it to stop.
the buzz comes from the armature plate not sitting squarely on the coil top. Could be due to dimples worn in the armature, the coil top is worn or the pivot points on the armature are badly worn and the armature sags.
the quick hack is stick a piece of electrical tape on the coil top or armature plate to dampen the vibration. You can also remove the armature plate and whack it with a hammer on an anvilt o remove the dimples. Sometimes filing the coil top works, sometimes you have to replace the coil.
'course, if you never expect to overflow the hopper, you can just disconnect the coil and zip tie the armature so all coins go in the hopper.