Slip rings/wipers
The slip rings connect the wires on continuously turning wiper assemblies to the rest of the game. The thin rigid wiper wires ride along the grooves in the slip ring hub.
The pressure the wipers exert on the slip rings can be adjusted by loosening the nut (circled in red) and rotating the wipers. The wipers normally have a slight flex. The trick is to try and hold the wipers with the tension you want while tightening the nut. When there is too much tension on the wipers, the metal in the slip ring grooves wears down.
The slip ring hub contains copper disks and bakelite separators.
Here is how the slip rings work. I removed one of the bakelite separator rings. The wiper rides along the edge of this copper disk. The disk can wear down until it reaches a hole, at which point you are in trouble. Notice the plugged hole - this is where a pin extends through the center hub. At the bottom of the hub, all the pins are connected to wiper fingers on the arms by wires. You can see the yellow, white, and red wires in the top picture.
The slip ring wipers can wear. The cup-shape on the end can wear down and snap off, and you wind up with a sharp wiper wire gouging the slip ring. I don't know how available new wipers are. I've only seen one game with wiper wear bad enough to need replacement, and I stole the wipers off a parts machine.
Slip ring wear occurs mostly on the search disk unit on early games without an R-Button.
If the copper slip ring disc itself is worn through, you'll be looking for a parts machine, but it can be practically any game if you are willing to pull the assembly apart and replace the worn copper disks.
