Inspect this circuit and if it looks good, diagnose it with Alligator clip jumper wires. Especially the Coin Unit disk.

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This is odd. To clarify, you can make the “1 to 4 Can Play”, display on the back glass any of the four possibilities 1 - 2 - 3 or 4, but still plays a four player game? Why this is odd! The unit that lights the 1 to 4 can play lights is the same unit that will control the number of actual players. Have a look at the fingers of the Coin unit; see if there is something odd there first.

Coin Unit, better name would have been "Number of Players" unit.

And any modifications, New wire or solder.... Player Up unit too, same sort of thing...

Insert on coin, one player game. Insert two coins, two player game etc. That's the history of the unit name. It served Bally well.

If the Coin unit and Player up units both look good, check contacts of the Jones plug. Which Jones plug is marked up on the schematic.

Clean the contact plate and contacts on the player unit and coin unit.
Check the player reset relay.

Most of the time it is the player unit not making good contact.

Looking a little closer at the schematic and your OP.

You can select the number of players but it always plays a 4 player game.

The coin unit manages the number of player for the game. The player unit is managing which player is playing. If you look at the schematic snippet that Howard has posted (Better Quality than mine) and Howard has drawn the path for a single player game.

Once the ball drains, the score motor starts as we have closed the Outhole SW and energised the Outhole RE. SW 3D will close as the scr motor rotates and this will fire the Ball Count Stepup coil advancing the ball count unit.(Single Player game)

If you play a 2 or 3 player game, the above will not happen as there is no connection from the SW in the outhole RE to the ball count step up coil until the Player Up number = the coin unit (Number of players). In this case when the ball drain, SW 4b will close during the scr motor cycle and fire the player up step up coil advancing the Player up unit.

If you play a four player game, you don’t actually use the Coin unit as describe above, see schematic below. Here I can see that it is possible to have a 1,2 3 or 4 player game and always having 4 players playing if there is an issue with how the Coin unit and Player up unit interact.

So what would make this happen? From the other posts, It appears that the Coin unit works, it also appears that the Player up unit works too. But not together. Not sure how the Ball Index RE is working here, It's purpose is to NOT advance the player or Ball count units if no points are scored for a ball when it drains.

I guess the issue is most likely at the Player up unit or the connection between them (Johns Plugs).

I have marked up the wire locations on the jones plugs with a red box.

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PS, Double check the Wire numbers for the Jones plug, my schematic is a bit hard to read. Think I have them right, after 3 goes.....

The contact plate is one of the very few places that should have some lubrication. I still have a couple tubes of official Gottlieb approved grease from 40+ years ago, but these days people are using the Super Lube Teflon Grease from http://www.pinrestore.com/Supplies.html.

Here's an extract from the 1973 Williams Fun Fest manual, though I wouldn't put any lubrication at all on solenoid plungers, not even the flaked graphite that this talks about.

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Hi Mitch +
I look at HowardR 's JPG in post-2 and at Chrisbee 's JPG in post-10 - I do not have an Bally pin - I have seldom had a look into an Bally pin. Mitch, - where are located (Score-Motor of course is in the cabinet) - Coin-Unit is ... ? - Player-Unit is ... ? Ball-Count-Unit is ... ? (Cabinet or Backbox or Playfield ?)

See my JPG - "blue S" and "brown S" are "drawings in the schematics" --- BUT in reality in the pin the actual wiring is either "A" or "B" or "C" --- and the actual wiring is important for troubleshooting --- can You look-up an tell: "wire-gray-red is wired in the pin like my blue-A or blue-B or blue-C" --- "wire-orange-white is wired in the pin like my brown-A or brown-B or brown-C" (?) Greetings Rolf

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