A few months back I shopped out an old Williams Contact that I had been given for free. There was enough acid damage on two of the boards that the two local board work guys I spoke with both recommended just putting in a rottendog combo board which I did. Displays are all bright and the sound and power boards all looked fine. The game has been working more or less great ever since I put things back together.

Except.

Contact has a moving target in the center of the playfield. Mine only works intermittently. Sometimes it starts right up at the start of a game. Sometimes it stays in place the whole time I'm playing. (20? 30? minutes at a time.) Other times it just cuts in and out.

The machine had sat non working for an unknown number of years prior to my involvement. Before I even knew of the issue, I added a couple drops of synthetic oil to the motor through the tiny hole. Not really sure if it was needed, but when the motor is running it runs nice and smooth. I'm not that experienced with repair, but I'm pretty sure I can rule out any issue with the motor itself.

More evidence to that point - the motor runs when this coil energizes and closes this switch.
coil (resized).JPG
If the motor isn't running, I can just press on the plastic bracket and it starts up as long as I hold it closed.

What I think and hope the culprit is: 41 year old capacitors.
While I replaced the MPU/Driver boards with a rottendog, and added fuses for the rectifiers as suggested in Vid's bulletproofing thread - I didn't really do anything to the sound and power boards.

I've not placed my order yet, but plan on ordering some re-cap kits for the sound and power boards. Before I do so - I want to ask about one other capacitor.

This guy here.
cap (resized).JPG
When I shopped the game out, this little disc capacitor was broken at one of the connections. I don't have them on hand, so I just soldered it back into place.
I assume this is something that I should replace as well, due to it's age if not for the fact that it had previously come undone?

Any guesses or suggestions as to other possibly culprits for my issue? Or am I on the right / most likely track?

Lastly - please help me source that disc capacitor. I have no idea what I'm looking for. I've found capacitor kits available at various places, but find myself absolutely confused trying to source the single disc capacitor. Any advice on where to find a single one of these things or a suitable replacement? Sorry to ask for the hand holding, but I really don't want to buy something that won't work.

Thanks for all the responses.

The photo that I attached was taken while the game was running. At the time, the coil was activated and the target was moving. I've never seen the motor not running as long as the coil is activated. Makes me think the switch itself is fine as far as gapping and cleaning. (I had previously cleaned it.) I'm trying to check to see if the coil is activated or not when the motor isn't running, but of course it's not cooperating. Since I decided to post this thread - it's been working fine the whole time. I can say though - right now if I start a game with the playfield up, the motor starts. If I tilt the machine, it stops as it should. Then, as it's waiting for a ball to drain that isn't coming since the playfield is up - manually closing the switch starts the motor at the slightest contact. I really don't think the switch is the issue.

Thanks! Part of my confusion in trying to find the capacitor online is seeing things listed with a uf number but not seeing that anywhere in the markings.
However - is that really supposed to be .01uf or .1uf?
I sent the picture to Todd at Big Daddy electronics asking if he carried them so I could order it at the same time as the cap kits for the boards.
He responded "It’s a 0.1uf (microfarad) 500 Volt ceramic cap." which unfortunately he doesn't have on hand.
I just noticed that there are a few identically marked capacitors on the power board that the schematic says are part no 5a-9072 - "capacitor .1mfd 500vdc"
I assume mfd stands for microfarad (M on the cap itself) and I actually need a .1uf? Sorry to double guess you - I just don't want to order the wrong thing.

Hmmm. It's a little hard to trace them, but the two purple wires lead into a bundle. One in one direction to the motor. The other leads in the other direction. At the motor, there's the one purple wire from the switch, as well as a 2nd purple wire that goes into the bundle and leads in the other direction.
My comically primitive drawing of what I mean
purple-wires (resized).jpg
There doesn't appear to be any splices anywhere that I can find. A foot or so further down the bundle, the two purple wires separate out on their own. (At least I think it's the same two purple wires - I can sorta knead through the bundle and I'm not seeing any other purple in there.) those two wires feed together into the head, connect by a molex and then lead into the power transformer.
IMG_5540 (resized).JPG
Disconnecting this molex shuts the moving target off, so I'm pretty sure I've traced them properly.

I pulled the connector at 2J12 and I'm not seeing anything out of the ordinary. Nothing that looks like acid damage nor burn marks. Everything feels snug, and looking into the female end - the contact doesn't appear loose to my admittedly untrained eye.
hard to tell, but that's the blue/black furthest to the left.
IMG_5536 (resized).JPG
Not the best picture/angle - but it looking directly into the holes, the little metal bits that connect with the pins on the male end don't look loose at all.
IMG_5537 (resized).JPG
At the other end - the blue/black and hot red wires seem soldered fine.
IMG_5539 (resized).JPG

Of course as I've been typing this up and taking pictures, I've left the game on. I can hear the motor running as it should this whole time, just taunting me.
Just going to leave the game on for a bit and check things out if/when the motor stops. I assume I'll find that the coil isn't energized at this time which I assume would point to something wrong with the blue/black wire? Or if it is still energized - that switch is somehow not closing fully?

Thanks again! Peace of mind is good.

OK - a couple things. I happen to have a local friend with a Contact as well. Had him check his, and the wires off of that switch are also both purple. However - his capacitor looks entirely different.

78849773_2491317584482713_5442104763854356480_n (resized).jpg
79410454_794179191010016_6214903726981775360_n (resized).jpg

He said he wasn't able to make out any markings. Any idea what this is or where to check in the schematics for what should be there?

While I was waiting for him to check his machine, I played a game on mine. Towards the end, the motor stopped when it shouldn't have. I lifted the playfield and can confirm that the coil itself wasn't energized. As usual, manually pushing on the plastic bracket would close the switch and start the motor.

So does this point the finger at that blue/black wire? I can certainly re-solder it at the coil. Don't have a replacement connector or the tool to re-do it on the 2J12 end, but can certainly order parts if needed.

Or is there still a chance that it's just an issue with power itself, and re-capping the power board would solve the issue? I still intend to do so regardless.

Thanks again.

The wire does in fact go through a black 24 pin block. Pulled it apart, but can't see any obvious issue again on either side. Everything seems really snug - no loose pins on one end nor loose looking receptacles on the other. Trying to jiggle the black/blue wire on either end of the block wasn't helping.

It's dark out here (Thanks, Winter) and I have terrible lighting where my machines are. I'll take another stab at it tomorrow since I think I'm working from home. Will try to follow the blue/black wire along the bundle to see if there's any bad splices or any other anomalies. Absolute worst case scenario - I can just bend the switch closed. Motor would run nonstop while the machine is on, but it's just in home use now anyway. Wouldn't really be running for hours on end. Of course it's going to bug the crap out of me if that's what it comes to.

Side point - but in reading things here and there while trouble shooting, I read that that capacitor on that switch is really just there to absorb charge when the switch opens and closes in order to prolong the life of the switch contacts, so I'm even further convinced that while I maybe should replace that capacitor - it's not the issue.
Example thread regarding a capacitor on a flipper EOS switch. In wonderful pinside fashion - it turns into a pissing match.
https://pinside.com/pinball/forum/topic/what-is-this-yellow-pack-by-these-flipper-coils