Hello all. I am currently working on a Williams Pat Hand ('75 EM) and had an intermittent issue where the score would start racking up the 1000's. If the ball drained, it would still continue over to the next player and keep running on the 1000's. It wouldn't happen very often. I cleaned up some contacts on the motor drums (pretty much anywhere it said "pulses 1000 point relay") as that was where I initially thought the issue was. I did manage to find a stuck closed switch in the area where I thought there might be the issue, but it didn't seem to help.

After spending some time on it today, I finally managed to get this to be a constant issue instead of a intermittent one and narrowed it down to this one thing... It seems that the 3000 point relay is sticking ON. I can start the game, play every switch fine, and then hit the one that is currently lit that awards 3000 points. When I do that the 3000 point relay pulls in and won't turn off. The points just keep going up and up... I can manually disengage the relay and of course it stops, but the real question for me is, "Where do I look next to get the relay to shut off?"

I can read schematics and understand the symbols and such, but sometimes I have difficulty wrapping my brain around the way the current is flowing around between the two sides. Any help would be greatly appreciated!

I also read the primer by SteveFury and was very impressed. It took some time, but it helped a great deal. Still not enough to solve this issue for me though. I'm pretty sure you guys can nail this issue in about 2 minutes, but I'm relatively new to doing EM work so, like I said, any help would be amazing. Thanks!

Before I sat back down at my computer to check different messages I just saw that in the schematics and wondered... could it be that simple?

So, if I'm reading that right, It would be the Fourth cam? because the first one is really the "index"? Then the switch would be the third one up? (I'll probably just check 'em all again...) Are there any other possibilities it could be?

The reason I ask is that this pin is sitting at a friends house and I hate to have to keep popping by. My schedule is open for this kind of stuff, but his... not so much. I want to have as many possibilities to rule out just so If for some reason that's not the one, I've got more tricks up my sleeve to get this thing finished. Thanks again.

So, I had no trouble finding the cam and the switch. Thanks for the link to the schematics. That's nice to have handy, and the fact that I can blow it up so I can read it is a double bonus.

Pulled the stack, cleaned the contacts, re-bent a few of the tabs on the backside, re-gapped the switches after reinstalling the stack and checked for proper operation (power off) when lifted and dropped in the cam. Started new game, same thing happened. I messed with it for several more minutes and got the cycling to stop by jamming a popsicle stick in there and then eventually readjusted the switch so that it stopped the cycling issue.

At this point the game is at least playable. Before, it would play fine until you hit the "3000 points when lit" switch, then it would run and run, continuously adding 3000 points. Now it just sometimes adds 1000, or 3000 but mostly 50 points I think. Not quite sure what is going on now... I would say I am very frustrated. I have not given up, and I've got permission to come over more if needed, but it's getting to the point of embarrassment.

While the playfield was up, I carefully checked all the switches I could see for proper gap, and tightened up the screws for all the different switch stacks and relay stacks. (The cam stacks were all tight.)

I told the owner, to give it a go and run it through it's paces this evening and let me know if anything else goes on, or if it decides to do the first thing again. I can always redo the switch stacks and wiring if needed. (Although I did test a few of the wires and had continuity where I was supposed to.)

Any more ideas would be helpful. Is there anything dumb that I should look at in the stepper units? Can that be an issue for this too?