What happens if you use a pair of jumper cables to jump 24V power from the terminals of the coin door lockout coil to the terminals of the U relay? Does the U relay pull in all the way and stay locked in until the varitarget lever resets?

Is he metal plate on the U relay riding properly on the hinge tab and not hanging up?

Ok, that gives confidence that the U relay is operating properly and does not have a bad coil.

But you say that when the score motor turns during simulated game play, the U relay just sits there and quivers (does not firmly pull in)? Next, I would test the motor switch 2C by shorting together the tab ends of that switch during simulated play and determine if the U relay will properly engage. At least switch 2C is easily accessible as it is the most outside switch (farthest outboard from the score motor axle) at the topmost level of position 2. You can find the brown-red wire and the other wire, which appears to be red-green-white.

If the U relay pulls in when you short the tabs on switch 2C, then you have a switch issue (either contact faces not fully conducting electricity or a failed (cracked?) solder connection where the wires attach to the tabs. If the U relay continues to quiver or spasm when you short switch 2C, you likely have a wiring issue or a failed solder connection at the red-bown terminal of the U relay coil.

Lee

Craig, checking resistance across a switch with a multimeter isn't "always" straightforward. Depending on the circuit involved, there can be other parallel paths with a lower resistance that are involved and the meter will read those paths instead.

Ok, your last post says that the U relay appears to be cycling in a pattern with (the rotation of) the score motor. If I interpret the schematic correctly, the U relay should stay locked on through its own hold switch until the Vari-target lever arms are reset and both arms are at zero position. It sounds like either your U relay is not staying locked on long enough to energize the vari-target reset coils, or, one/both of the zero-position vari-target switches is not conducting when the lever arm is pushed in.

Try to check out: 1) the hold switch for the U relay (green-black wire) and make sure that is clean and making good contact when the U relay pulls in, and 2) the vari-target zero position switches are closing/conducting when the lever arm is pushed in. To be clear, the zero-position switches are the ones with the green-black wire where the end of the switch is in a vee shape and it rides on the edge of the bakelite.

If you still can't resolve, maybe I can take some close-up photos of the involved switches on my machine and you can check the gaps and positions of your switches vs the photo.

Lee

Craig, as of today, I'm out of town for the long weekend, away from my machine and the schematic. Hopefully, someone will have some ideas for you.

In the meantime, I would suggest proceeding to locate the tilt relay on the schematic and read across to determine the number of tilt relay switches in the game. Should be 4 or 5. One will be the pendulum tilt and another the ball roll tilt mechanisms, but there will likely be at least 2 other normally open (NO) switches that when closed, will energize the tilt relay. I am guessing there will be a weighted NO switch attached to the underside of the playfield and maybe another such switch located in the backbox. Try to find all the tilt switches and inspect their operation. One of the switches may be gapped too close or have wires that are making intermittent contact.

Grreat.
Sounds perfect. Playing some Play Ball on the July 4 holiday!