Please read this entire document twice before you do anything:

http://www.pinrepair.com/em/

Yes, what wayout440 said above... get familiar with the machine and its components..

If you are gonna take things apart (stepper units, score reels, etc) take LOTS of pictures and don't get too far ahead of yourself. The guys here are willing to help. They have helped me! If you feel your getting frustrated.. walk away for a bit.. I've been there, done that.

Two very important points mentioned in the links:

1. When you have a partially functioning EM game resist the urge to go through adjusting everything all at once, as most of the time this causes more headaches than it solves.

2. Never use flammable contact cleaner.

I find it best to get the game 100% working before starting more in depth restoration. It really helps to know for certain that something worked before teardown so you know "it was something I touched" during the subsequent work.

Print the schematic so that you can stand over the machine with the schematic in hand, then just look at things until it clicks in your head. If you're going to fix it, you're going to have to understand what you're looking at. Once you understand what you're looking at, it should be easier to work on. Sorry I don't have better advice, but that's what worked for me.

Good luck with it.

Have a look at this post to understand how pop bumpers work: https://pinside.com/pinball/forum/topic/pop-bumper-model

Then check the end-of-stroke switch on the sticky pop bumper.

EM pins often have options you can control with the plugs you show. In your picture those plugs are for giving out awards at different point thresholds so it is normal that not all of them are plugged in.

I almost purchased that thing a few years back.

Don't know off hand but they get toasty, not uncommon to see the label burned off.

When you say “stuck” I assume you mean locked on.
That is very bad. If the coil is locked on for more than 5 or 10 seconds it’s gonna melt. They reach well over 400 degrees extremely rapidly. It may take longer on EMs but not by much. Hot is bad. When trouble shooting you want to quickly find the locked on coil, attempt your fix, and then let it cool off and see if that fixed it.

Chances are the contacts are oxidized/corroded. Get some 800/1000 grit sandpaper (nearly NO bite) and cut small strips and fold it in half, put the paper in between the contacts and hold it closed. Rip the paper out a few times like you’re ripping a credit card through. That’s all you need to clean contacts. Don’t use a file. Anyone who says “file the contacts” is ruining machines or has misspoke and what they mean is “fine sandpaper”

The other chance is that the switch is tapped too wide. Be very careful adjusting them. If you accidentally close them and it stays closed then you will cause a lock-on/reset issue.

Been using point files for some time, does take a light touch though.

Get one of the flexly files from PBResource, they work well.

That’s a different point that I didn’t want to get into. I have used the PBR files before but they’re more like nail files then the harsh metal files I see most people go use when they hear “file the contact” so I try to not even mention it at all. But yes, those PBR ones are specifically made for the purpose of gently cleaning contacts. And if you’re careful you can use others.

Blue sparks:
Those are normal in most EMs. It’s because the contacts are dirty, they spark a little bit. It’s harmless but that’s all the black dust you see stuck over everything. If you use the 800/1000 grit sand paper or the special contact file from PBR the sparks will stop. And the game will stay cleaner.

You'll never get all the sparks on an EM to stop. It's not the condition of the switch contacts that causes that.

Mostly agree on cleaning the contacts but some like flipper button switches will require a metal file. Just don't go nuts with the it.

I'm glad to see someone finally bought that...I had considered it several times over as it was near me. Too many projects scared me off, so I'm glad you're giving it a go. Good luck! The story behind it alone seems like it is worth it.

Lock relay coils are extremely high resistance and are designed to be on for long periods of time. They will get warm. The wrapper will get toasty. Overall, I wouldn't worry about coil temps. And while you don't want them lo lock on for long periods a pop bumper coil will not melt in 5 to 10 seconds. It takes a bit more than that.

This is something I had wondered myself.
Is there a limit to how long EMs can safely sit? I mean if the game sat in an arcade in the 70’s for 12 hours or more, then does that mean that is still acceptable? I worry that with age the lock relay coils may be more susceptible to burning up.

Well, over time, sure, but not just in a one day setting, they won't burn up.

Now, a bumper coil or some other coil with a lower resistance will go a lot faster, but I've had them locked on for a minute or so and they're fine. I am not about to try and see how long it takes, but I know that if they lock on for 30 seconds or so, they'll generally survive. The sleeve might eventually melt and you wouldn't be able to get it out of the coil. In the old days with metal sleeves they were hard to get out anyway. I've thrown out coils that were ok because the metal sleeve was dicey and removing it will sometimes destroy the windings. They just come apart.

Lock coils are really high resistance and are designed to do what they do. They'll got toasty and the wrapper will eventually get smoked but they will last a long time.

The designers back then knew that the games were going to sit on for long times so they put in a coil that could handle it.

If you turned a game on and left it on for 24 hours and came back, the lock coil would be pretty warm but it would still be functional and would continue to be for quite awhile.

I had a Gottlieb popper coil get locked on and in a very short period of time smoke was rolling out the cabinet door!

The game may have been high-tapped. Just one more reason you should never do this needlessly.