Hello! Just started work on a 1972 Grand Slam machine, and I wanted to get some help and opinions before tearing into it as it will be my first EM pinball I've worked on. The machine had certainly been sitting a while before coming to me; all the playfield rubber was fallen off and thrown about the board, dust and first everywhere, ball itself was rusty, etc. I cleaned it all up, checked all the fuses and fixed any obvious issues in the wiring, then went to start it up to see what was/wasn't working. The main motor switch made it's full rotation and came to a stop in it's resting position, start relay activated and the start motor also made it's way around, ball count motor in the rear resets itself, all the playfield lights came on, and it spat the ball in to the shooter and then... nothing else. None of the scroll wheels on the back box reset themselves, and all of the playfield targets, switches, flippers, etc. remained unpowered. I've tried looking through other forum posts but couldn't find explanations of quite the issue I'm having (everybody seems to say that if the back scrolls don't reset, the main switch motor will constantly turn, mine doesn't reset the scores but still comes to a stop?), and I've read through the instruction booklet that was included with the machine but it is relatively vague. I've worked on a couple solid state pinballs previously and have plenty of experience working on other period EM machinery so I'd love to fix it up myself if anybody has suggestions to try out. Some general pics of the machine included in case I'm missing something obvious. Thanks! IMG_20231117_074551802_HDR (resized).jpg IMG_20231117_074600049 (resized).jpg IMG_20231117_074614577 (resized).jpg

Definitely! Especially with the ball in that condition and all the dead rubber, I didn't even shoot it down the field--just looking at was/wasn't working. Once I get all the switches working properly I'll be going through cleaning up the playfield, new ball, fresh rubber all around before actually playing on it.

I was doing a little more digging and noticed the V relay was intermittent, at best. When I activated it manually the Z fired and all the scrolls reset. Seems like I'm on to something there. Some of these old wiring diagrams make my head fuzzy, so correct me if I'm wrong, but it seems the V should be getting power off of S firing during the initial start sequence right? I cleaned the contacts and took the V relay off to measure and bench test it, 16.3 ohms resistance. Not sure if that's normal for the age; I've seen them listed as 15 ohm resistance new but I figure that's within tolerances.

Didn't catch that about the Zero Position switch before, good to know! When I start a game, the solenoid on top of the Ball Count unit fires, resetting it and opening that contact with the R+W wire I need. Should this unit advance itself one stage after resetting to close this contact back up and activate the playfield?
Added images on the unit as it sits after the start sequence fires.open r+w wire contact for zero positionIMG_20231117_093948803 (resized).jpg

Good advice! I didn't fully disassemble, but went through and cleaned/lubricated all the motors and score wheels with appropriate grease. I've been cleaning contacts as I go, but I'll probably have to commit an afternoon to sit down and pretty all of them up. I went and cleaned the motor, pall, and all the contacts on the ball count unit and after looking at the other advice so far in the thread I'm thinking that's where my issue lies.

I went ahead and disassembled all of the V relay area, cleaned all the contacts, resoldered each connection, and took both relays out for inspection and thorough cleaning. Wouldn't you know it, start sequence works perfectly now! I love how robust these "simple" mechanical designs tend to be. I was on my way back here to mention that I could manually advance the stepper and the board works, and saw your comment about the trough switch. Sometimes the easiest solutions are the answer, huh? Had the playfield up the whole times I've been working on it and didn't even see that switch there ever. Sure enough, hit it down and the stepper advances, game is fully playable minus the big rotator in the middle and needing some good loving all around on the playfield.
On a side note, do you have any suggestions on how to reattach the old paper labels for everything in the machine? A few have fallen off but they're all there, and I'd love to keep it original if possible.

Thanks for the great help! Machine is well on its way to revival now!