Cams Not Indexing (Stopping)
|Case Study Summary|
|Games Applicable To||all|
|Problem Reported||search wipers not locking in index/home position|
The cam locking notches in the bakelite disks can wear. While some wear is normal and inevitable, wearing enough for the indexing/locking to not work is fortunately rare.
Before assuming that a slightly rounded notch lip is your problem, make sure the indexing plate can drop all the way into the notch, and the clutches are lubricated. If you put some extra pressure on the relay plate/armature with your finger and it still won't hold - or the cam releases as soon as you let go - then a worn notch is likely your problem.
You've got the usual three options:
In this case, there's not much difference between repair and hack. You can't add back bakelite that is gone, and I doubt something like epoxy would hold up to the forces without chipping off eventually (but it might). Somehow you need to make a sloped notch wall vertical again, and the simple solution is to file/cut the slope out so you have a restored the vertical notch wall.
On many machines, the locked position of the search wipers is flexible. There's an arc of rivets under the wiper contacts that aren't connected to anything, so if the locked position varies +/- a rivet from the standard factory setting, no harm done. In fact, the normal factory position has the wiper contacts between/bridging rivets...all that matters on some games is a switch stack is lifted by a pin when the wipers are locked. If you cut out the slope, the locked position of the wiper fingers will shift a little, but you can adjust the switch stack if needed to be back on the pin and you're good.
On many of the six-card games, though, the wipers must be locked on a specific rivet - it's the only one that isn't connected to game circuits. Get it wrong, and the payouts will misbehave. If you cut out the notch, the wiper contacts will likely shift and lock on a rivet that is connected to game circuits. You get payouts on cards when a win is detected on a different card.
The simplest solution on a game where the wiper lock position is critical is usually to cut the notch and adjust the index unit and switch stack position so the wiper contacts are in the correct place when locked. Depending on how much you have to cut, you may be in the adjustment range of the parts and you are done.
If you cut out more than the adjustment range of the index unit/switch stack can handle, you'd need to elongate the slots in the mounting brackets so you could move the part more, or worst case drill and tap new holes for the mounting screws.
If you are willing to take the shaft wiper assembly apart and have a parts machine, replace is an option - either just the locking cam (That's what Robert did) or the entire wiper assembly if it's the same.
I suppose it may be possible to remove the cam from the wipers and flip it/reposition it, remount the switch lifting pin (in any), cut a new notch in the right place, and slope the old notch even more so it does nothing. Seems like a lot of work compared to just cutting the existing notch and moving the associated parts as needed.