Quoted from Slips:
Sorry if this is off topic but what is the best way of carefully adjusting and cleaning switches?
You'll get a lot of different answers on this one, so I'll give you mine.
You need an adjustment tool that you can buy from PBR. I like to take the boards out of the game where I can put them up on a bench and see them clearly. If you don't have the time or want to do it this way, you can clean them in the game. Just make sure you have plenty of light, especially when dealing with short frame Gottlieb AG relays that have very little throw. If you're using a flexstone, pinch the blades closed when you file to get both points.
Regular voltage contact points can be cleaned with a flexstone file. I have one I still use, but my go to now, and others on here, is a wire brush on a Dremel tool. You can clean them very quickly using one of these and it does a great job. It works better if you unscrew the relay from the board. It works even better if you remove the switch stack from the relay itself. That's a bit more advanced to do that so a flexstone file might be your best bet.
On adjusting, the first thing you should always do is tighten down the switch stacks. Over time, the bakelite spacers dry out and shrink and the screws get loose. Tighten then up, doing the screw closest to the blades first. Then, use the adjustment tool only on the short blade, not the long blade that inserts into the armature. It's a balance between getting it too close which can cause vibrations to accidently close the switch, and too far apart and it won't close. I adjust mine to where you can see a tiny bit of deflection on the short blade when the switch closes. One of the banes of EM games is the switch that looks like it is making, but isn't, and the converse, the switch that looks like it is opening, but isn't.
I guess I can be accused of using the so called "shotgun" method of cleaning and adjusting. What I say to that is, I get these games, quite often pretty dirty and quite often barely working, or not working at all. To me, it makes a ton of sense to clean it all up. I figure, yeah, I can only fix the parts that are keeping it from working, but eventually another problem is going to crop up. So I do them all. It takes time. It's tedious. You basically are looking at every single switch in the game. However, when you're done, assuming you have checked to make sure every switch is doing what it is supposed to do, you stand a pretty good chance of the game operating perfectly. It doesn't always happen, but then the adjustments are easy to make and you're good to go. I generally don't have to do much with my games once they're are restored like this. I know it's not from everyone, and often it might not be needed, but it has worked well for me. I've been doing this for awhile and my experience level is higher, but still, you're never going to learn how to really work on these games unless you really work on them. Being scared to dive in there and get your hands dirty and learn how to do it isn't the way to go, IMO. Now, if you've never worked on a game and you buy a Grand Prix, then all bets are off. That's the only game I've ever been afraid to do this on. It's more complex and it's crowded as hell in there but still, if you pay attention to what you're doing and take your time, you'll be ok. This is not building the space shuttle here.