Because I'm a moron, it took me a while to figure out my lane lights weren't alternating as they should; they'd just stay on and never change lanes. I got under the hood and fired up a game and saw that the coil on my alternating relay would energize and stay that way, pulling the relay into the one position and never releasing it. So I found the cause...kind of.

I traced the schematic upstream and the next thing in line is a capacitor and 2 diodes. I've added pics of them, both in the schematic and under the playfield.

So...the question: Could it be a failed cap that's causing the coil to stay on? Or a diode issue? Easy enough to replace them, but didn't want to bother PB Resource for those parts before checking here first (also saw that the schematic says 47 microfarads, but the actual cap in the game is 50 microfarads - not sure if that's an issue). Not sure of the diode rating, either, since the schematic just says "100 P.I.V. Rectifier".

I've also learned that the score motor relays could possibly cause issues with the alternating relay, so wondering where to look there if that's the case.

I know this is a common issue with C37, so I'm hoping someone can lead me to a solution. Thanks in advance for any help!

EDIT: Because Pinside did something funky with my schematic photo when I rotated it, I'm just including the original, which is sideways.

20170409_190042_resized (resized).jpg

20170409_185808_resized (resized).jpg

No problems with scoring. I just thought that a blown cap or diode might cause the coil to stay charged. Not sure what else would cause it

Thanks to all for the responses. I'll investigate tomorrow or Tuesday and report back with what I find!

I DO see it flicker when it plays. The lights go off and on again without switching to the other lanes. I think you're on to something...and I definitely think it has to do with the match relay because I noticed that it wasn't moving freely and coming up with random match numbers at the end of games.

Awesome. I know where to start looking now. Thanks so much again for everyone's help!

Okay...I looked at the FS mini-stepper relay in the backbox, and it's going to need to be rebuilt. The match number never changes, so I'm hoping a disassembly, cleaning, and lube on the disc will help things work better...and fix my alternating relay problem. I'll post updates when I get to it. I'm swamped with my Joker Poker just now.

Thanks, Rolf! I'm going to check my diodes to make sure both are operating properly. Seems like if I address a couple different issues, that should solve my problem.

Okay...first of all, the diodes were working properly.

It was the AS relay (labeled the FS relay on my C37). The fulcrum pointy thing wasn't moving the ratchet on the spindle consistently so I took it apart, cleaned and lubed the shaft and circuit boards (not the ratchet or actuator, obviously), and reassembled it. When I tested the ratchet, it still seemed a little sporadic, as if sometimes it wasn't catching the teeth of the ratchet. The ratchet is fine...not worn that I can see. I think the problem is the amount of force being exerted downward by the actuator...it's not catching all the time. Not sure how to fix that since there seems to be some small wire thing in there that acts as a spring.

Anyway, I put it back in and everything works now, but I think it sporadically doesn't (which is to be expected). Does the 1000 bumper change the lights? Because mine doesn't - only the top two bumpers fire the alternating relay.

Thanks so much for all of your help - I'm close to having this back to working perfectly!

This thread is a perfect example of why Pinside is great, btw. Would've been a bitch hunting down what was causing the problem. This place is just a huge knowledge pool waiting to be tapped. I'm sure I'll be back with another problem soon...

Everything is perfectly aligned. Just not sure I have the proper amount of downward force on the teeth of the little plastic gear. I think the actuator may still be slipping a bit...and I have no idea how to fix that.

All the parts are there - and your picture shows perfectly what I'm talking about. That little plastic piece doesn't seem to catch the teeth on the wheel all the time because it doesn't press down hard enough...or so it seems.

No spring visible. There are two tiny wires that come out of the back of that actuator, so if you press down on it (toward the wheel), it springs back. Perhaps some tiny spring inside or just a wire used as a spring. I don't really want to take that apart to find out because I'm afraid of messing it up.

Absolutely no worries, my friend. I had no idea the lights were supposed to alternate until I watched a YouTube video and played another guy's machine that is local to me. You sold the machine in good faith and that's how I bought it...and this is teaching me something about EMs, so it's actually a good thing. I'd buy from you again in a heartbeat - and that's a good thing because we're running out of Caribou and maple syrup!

Thanks...I figured as much about the disassembly of the pawl (and thanks for teaching me what that part is called!). I thought about putting lube on the metal cam wheel (that comes into contact with switch), but didn't do it. I did check the drag and it was fine. I also cleaned the circuit boards and sanded them with 1500 grit sandpaper, then put super lube on. I know about all that stuff (and I'm not dumb enough to use WD40). But I used super lube on the plastic shaft. Didn't lube the cam - didn't even know about Tri Flow, but will get some now! I did take both side off at once - didn't really find it a problem putting it back together...just have to get the little metal piece in the middle to line up with the screw holes.