Top Score: player 2 reset issue

A new problem creeped up on Top Score and it took me a little bit longer to fix than I would have liked.  Partially because of my big trade, partially because I've been busy, partially because all pinball time has been spent with Monopoly, and partially maybe kinda because of a stupid error in overlooking something basic on my part...

Here we have it:

Player 2 tens unit was not reseting.
This mean the circuit of zero-position reels never finishes closing, and so the motor is stuck in an endless loop.
KA-CHUNK-KA-CHUNK-KA-CHUNK.

You work on EMs, you know the KA-CHUNK-OF-DOOM.  OK OK, not really doom, it just means something isn't right, and now that I know what I know, it's not that hard to figure out.
Let's not forget, on my first machine ever this type of problem stumped  me for almost a month.

This is your motor:

 Pretty basic, lots of stuff that can close at various times and having it ka-chunk-a-chunk forward.


And here is the important part of the player unit:

Remember that the player unit (the big wheel in the head) controls which player + ball it is, and has a few steps for the reset cycles.  Playing each ball of each player, then reseting at each steps, completes the 360 degree revolution.
We've seen this before, the reels need to all be in their zero positions for the NC switches to allow a signal since when reseting player 1's score reel, P3E is open.  When it is time to clear player 2's reel, P4E is open, so the player unit won't go anywhere until they have all hit zero.

What's next?  Figure out what advances the 10's unit!

the N relay is "add 10 points" and M is "add 100 points", pretty basic, and we can see how it goes to either reel depending on which player switch is set.
But then we see the lines for the runout switches and P3A, P4A, P3B, etc switches.  These are parts of the reset circuit.  We can deduce that easily because it's the runout that is open at zero, and closed for 1-9 on the reel.



I started by examining the score reel in question, and cleaned the switches in it's back:

The switch stack on the back of each reel

I never knew this before, but these things have modularity in mind.  Bend back the plastic at the lower left and each unit slides right out!

After this I went on to the back of the player unit.  Which was a bit naive, sure, but it was dirty.  I followed Clay's guide and cleaned the rivets with alcohol, sanded with fine paper, and then applied some contact grease.

I did not disassemble it, just did half, stepped the unit forward manually, then did the other half.

I love this feature:  Takeout one screw and the whole player unit comes down over 90 degrees for maintenance.

So that didn't do it, and I kind of knew it wouldn't, based on the wire colours of the schematics, but I wanted to do it anyways.
I also made sure to tighten the switch stacks, closest to the contacts first, the the other screw second.


To get to the issue directly, I just checked the back page of the manual:

according to schematic, 2nd 10s unit is controlled by P4A on the reset cycle.  We can easily find the cam and switch that is.

The P4 switch stack is the one immediately below the small one.

So my dumb error in all of this?  When I originally cleaned this stack I just didn't really look hard enough and though I was cleaning P4A but actually cleaned P4B.  Ooops.
I got out my trusty contacts file (via Steve Young at Pinball Resource,) did a manouver where I threaded it through the upper stack gaps and got it in to the P4A contacts and rubbed.

Went back to the front of the machine, ran a test, and yup, perfect reset.
Problem solved.


Why does this happen?  Don't forget that this is a relatively significant amount of electricity jumping between these switches, and 40+ years of that leaves corrosion.   That's a big part of why shit on these machines just starts going a touch wonky, and will continue to do so.  But by logically tracing it back, you can always get it working again.
And if you ever want proof, just open the back box, turn off the lights in the room, and have a friend play pinball while you watch the sparks fly!

This most likely will be the last of my Top Score posts, as the owner will be selling it soon.
Oh, what to do with all this free space?  No worries, I have a summer project lined up.  :)