You may have ruined the switch contacts by filing them down.

I usually pinch the switch and run an index card between them to clean the black carbon & tarnish off the contacts.

When adjusting the gap between the two leafs, I usually attach a multimeter to the tab of each one so I can hear when they actually make contact.

For EMs, I believe the high voltage current contacts will be just fine with some light burnishing using flexstone. It's the Solid State games you have to be careful of--gotta use an index card for that.

The thing to remember when filing contacts is that you have to file down lightly (just enough to remove corrosion and crud) evenly and flat. A common error to make is burnishing to vigorously or on a slant, then your contacts wont make a good flush, complete "mate" when closed. It's entirely possible that you just didn't get enough crud off with the flexstone.

I remember reading long ago that the black "soot" that forms on the switch contacts from the oxidizing reaction is actually a conductor of electricity, except when there's a ton of it caked on the switches.

Heh, didn't catch that this was in the EM forum.

I use a metal file for all of my EM contact cleaning. Lightly for the most part and heavy on tungsten points.

You won't ruin EM switches with a flexstone or a metal file, unless you file them completely away.

Those contacts must have been really, really corroded if a flexstone didn't fix them. I think it's more likely they weren't making good contact and you flattened them out more with the metal file.

Sometimes, the contact rivet becomes loose on the blade. I have had success soldering the contact to the blade in this case.

yup, that happens too. solder, or a squeeze with a pliers to smash the rivet back on tight. "careful not to damage the surface".
the best way to clean contacts,"imho", is a dremel tool, with a brass brush. it gets all the crud, and shines the contacts up nicely.
then a little compressed air to remove any bristles left behind.
each contact is a new issue, some burned, bent, just dirty, loose etc.
but for general cleaning, you cant beat the brush.
it also works great for prepping solder tabs and wire ends for soldering, gets all that solder repelling tarnish off, and resolder is easy.

If it's a large contact, like an end of stroke switch, you need to use a hard file. They will quickly ruin a flex file and won't be cleaned properly.

For more common small contacts, you can use either type of file. And don't do this stuff with the game on, that's a bad idea.

You can use your finger or a hard file or something else to press contacts closed while cleaning to create resistance.

I like fine sand paper, 320 grit seems to work well. I fold it over so both contacts get sanded at once as I pull the sand paper through.

I like sand paper because it is thinner and I think the contact surfaces are more likely to stay aligned when I sand them with paper compared to trying to fit in file.

Generally I like to try and use a business card first before filing and that often works.

The problem with many pins, even SS pins with plating on the contacts is someone before you owned the pin has taken a file or sandpaper to the contacts and taken the plating off. So using sandpaper or a file will not matter and the contacts are likely corroded because the plating is gone and you will need to use sandpaper or a file to get them to work again.

I think a call to Steve at pbr is in order.
he has a lot of contacts. prob can order by the blade purpose, EM or SS like, EOS contact, or score relay contact etc...

It's best to know your parts numbers when making that call

I also prefer sandpaper, 400 grit. A pair of needle nose pliers to add a bit of LIGHT pressure helps too.

Just get some of both to have around. You'll use the tungsten ones for EOS switches (cabinet, flipper, etc), and the others for probably everything else. Except the little tiny switch contacts, which you'll have to salvage some parts switches for.

Sometimes the grit from the flexstone or sandpaper stays in between the contacts after cleaning, I like to run a business card dampened with rubbing alcohol through after cleaning with the flextone or just blowing the switch out with canned air after flextoning to blow away the grit and dirt and metal filings / residue left from filing.

Yes, run through a business card after sanding/filing to get out any grit (though I use a dry card). That is something I also always do and forgot to mention.