B-F, You said this was your first EM, so I'll be very basic.

There are actually 3 switches involved with a single slingshot. There are 2 switches that protrude vertically on the top of the playfield and sit right behind the slingshot rubbers. When they close, these switches deliver DC power to the solenoid that operates the kicker arm. The 3rd switch is mounted right underneath the playfield near the top of the plunger for the kicker arm? That is the switch that actually routes pulses to the the 10-pt relay. It is normally open, but closes when the plunger for the kicker arm gets pulled into the solenoid. See the photo below.

That switch is usually the culprit when a sling kicks, but does not score points. Inspect that switch, clean the contact faces, and make sure they close when you manually depress the plunger into the solenoid core. Also check that all wires attached to the tab ends. See if that fixes the issue.

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Great that you have the game one step closer.

I'm not sure exactly what the --J-- designation stands for, but after comparing the schematics for my late 70s Williams EMs, it seems to indicate circuits that are running DC voltages.

Lee

B-F, The Rolf Meister has provided pertinent suggestions to investigate the coin unit.

To expand on that, the photo below shows an image of the solenoid side of a Williams coin unit from your machine's era. Rolf is telling you to observe the coin unit with the PF up, while pressing the start button, and that are two likely possibilities that may be inhibiting a 3- or 4-player game.

The clock spring is shown roughly in the center of the photo. It could be that the spring has too much tension and is resisting the mechanism from advancing past the 2-player position. In that case, the entire mechanism may need cleaning/degunking, or failing that, the clock spring may just need to be "unwound" one turn.

The 2nd possibility is that the switch near the left center of the photo is being opened too early. That switch is in series with the start button and will disable the start function when it is open. It is only supposed to open when the coin unit has advanced to the last (4-player) position. It is mainly there to prevent a customer from squandering credits if they should accidentally press the start button when the game is already set for 4 players.

Lee

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PS: the photo in my post above was taken with the coin unit advanced to the 4-player position. The switch on the left side (On the schematic, Williams calls it "coin unit last position bk switch") had just barely been opened by the white peg on the gear.

Don't spend a lot of time trying to budge the wiper arms; it's all about rotating the bakelite plate.

Sometimes you can rotate it even if you can't manage to loosen the screws; it doesn't need to move much. Try hooking your forefinger under the lower right-hand corner (assuming you are facing the wiper side) and pressing down with your thumb on the top surface of the upper left-hand corner and use a wiggling motion. If that doesn't work, you might try the smallest, daintiest hammer you own and tap lightly down on the upper left-hand corner (tap it, not hammer it). Again, you only need to move it a mm, or so.

Congrats on getting the game fully operational! Sounds like you've been learning a lot for your first EM. The late 70s Williams EMs were a lot of fun. The final step in the repair process is to play a lot of test games