I'd get an outlet checker. Then plug it into the service outlet. Then you'll know if the wall and the game are wired right or not. If it shows an issue, then I'd just try the outlet. Then you know which way to go. Wall or game. Something is wrong.

LTG : )

I agree with checking the outlet. However GFCI outlets can test good with a circuit checker and still be faulty. The circuit checker looks for ground, 125VAC and neutral. As a GFCI ages, they can get weak and trip easier than they should for no good reason.

You can also install a regular outlet, unless outlet is located is located within 4 feet of a water source or in a garage (code) and then install a GFI circuit breaker in the box. If outlet is using 12 gauge wire you can go with a 20 amp GFCI breaker.

Did you change the actual line filter as well?

The GFCI Outlet will trip for one of two reasons, overload on the circuit, or a ground fault, assuming it is not damaged. It could stay energized and show no signs of problems with nothing plugged in and still have an issue on the electronics inside the GFCI. I would suggest that you unplug the machine and plug in some normal load, like a vacuum cleaner, for instance and see if the GFCI outlet operates normally. Assuming there is no problem with the GFCI, you probably have a ground fault inside the machine and it might be hard to find. A ground fault would be an incorrect connection from the green ground wire to the white neutral wire in the machine. The GFCI outlet would trip for this condition and the circuit breaker at the panel at your house probably would not trip for this problem, unless that circuit breaker at your panel has a ground fault element in it..

You mentioned that you replaced the line cord to the machine - Did you replace the cord cap (The end that plugs into the wall) or was it a molded end piece that you didn't have to mess with?

If you installed a cord cap, open it back up and make sure you don't have a whisker (single strand) of the wires out of place.

If this is a new cord with a molded cord cap, use a meter on the 20 M setting and measure from white to black, black to green, white to green. You should see high (near infinite) resistance. If not, then disconnect the end of the cord inside the machine and measure again. If you do not see infinite, you got a bad power cord.

Assuming the GFCI is good, then there has to be something wrong with the cord or cord connection. I don't see anything jumping out at me in your pics.

Is the line input hot and neutral backwards at the filter? Shouldn't it be white to blue, black to brown?

How much continuity between the hot black wire and the grounded braid directly behind?

Your blue and brown coming out of the filter are reverse of the ones in the second pic. So maybe the black and white from your line cord need to be reversed from what you have done.

I'm not sure how the filter being wired backwards would cause the GFCI to trip with the machine turned off, unless the filter is bad.

It might not trip the GFCI but hot chassis are not a good thing.

Electrician chiming in here. This is false. A GFI trips for one reason only... a ground fault. It does not trip due to an overload! It is not an overcurrent device in any capacity.

GFCI and GFI are not exactly the same. https://bates-electric.com/gfi-vs-gfci-outlets/
"The main difference between the GFCI and GFI terminologies is that while a GFI is local, the GFCI is used in the context of both a local receptacle and a circuit breaker which provides ground interference protection for the whole circuit."

And it's a bit misleading to say they trip only on a ground fault because that can lead people to only look for a problem on the ground wire. They will trip on any difference in potential and that could be faulty ground wire or neutral wire, wherever there is a difference between current flowing in and current flowing out. That's one reason you can install one of those outlets on an ungrounded circuit and still be protected.

You are correct, most GFCI outlets do not have overload trip capability.

When I mentioned that there is an incorrect connection between the green and white wires that creates a ground fault, that means anything in those circuits that those wires connect to. The problem could be in the plug, the cord, or in the machine somewhere. It could be hard to find.

I feel compelled to mention that problems like this are sometimes the reason why metal rails on the side of the machine will shock you if you are touching an adjacent machine's rails that are grounded properly. This is an unsafe situation and I suggest that you try to locate the problem, whatever it is. GFCI outlets are primarily used in areas where water is common, like the bathroom and kitchen, to prevent people standing in water and being electrocuted. The same principal applies to the pinball machine if there is a ground fault inside it.

Maybe. Measure the resistance to ground from the braid to the ground wire where the cord enters the machines on both the Mata Hari . They should both be zero.

When you touched the braid and tripped it that means you touching it changed the potential, probably providing a better path to ground. The braid should have a good connection directly to the ground wire on the cord, you touching it should not improve the ground path at all.

I bet the malfunctioning Mata Hari has a small milli-amp current getting onto the braid from somewhere.

the filter is balanced, the “polarity” is irrelevant. But it does have capacitors to ground, so if they’re leaky, it will trip a gfci. Also if the circuit is fed by an inverter (ie solar) the high frequency content could trip the gfci, especially if it’s a very sensitive one. You can eliminate the filter to see if that solves the problem. The machine will work exactly the same without it, but could cause potential radio interference, especially to nearby AM radios.

In 25 years in the trade I have never seen ANY that have that capability. If you know of one that I'm not aware of, please share. I will spread the word, seriously.

What does your meter read when both leads are together? In other words, what does your meter read when it should be zero?

Also, what does the ground braid to the ground prong at the wall end of the cord read?

Have you disconnected the cord from the filter and verify that the cord itself is good?

I think they are close enough, both have a good ground connection.

You might disconnect the braid at the transformer and connect your meter in line between end of braid and transformer lug. Set it to read milli-amps. Any current flowing? If not maybe disconnect the ground for the service outlet and connect that to your meter and your meter to ground. Any current flowing that way?
I'm trying to think what's hot with the machine off. Should have current flowing through the service outlet, then to the switch and it should stop there. If you're getting a small current draw maybe bypass or disconnect the service outlet and see if it goes away?

Is the ground braid even connected to the service outlet or cover directly?

I have observed a damaged GFCI outlet trip on a 10 amp load test with no ground fault current applied.
The outlet was not designed to trip on load, but since it had problems with the circuitry inside, it did just that.

Some peoples answers really make me laugh...... Gfci's measure the current from hot and neutral independently, if there is a difference (depending on letter grade of gfci) it trips. All current entering a load SHOULD BE the same leaving the load.

If you are getting mildly shocked from one game to another or to the floor from a game, it's because there are eddy currents that want to go to ground of grounded/bonded pinball metal that cant due to an interrupted path to ground, broken ground prong ect., you might ask yourself why this situation doesn't always trip a GFI. it's because most of the time that Eddy currents are induced from magnetic lines of flux from the transformer and have nothing to do with the total current between hot and neutral of the machine.

Years ago, I had a GFCI outlet that would randomly trip in my basement, maybe once a week. Funny thing was that I'd sometimes hear it trip as I was coming down the basement stairs. I had about 8 games plugged into the outlet. Over the course of a few months, I'd unplug a game to see if the GFCI would trip and narrowed it down to my Baby Pacman. I ended up finding a washer that had come loose from somewhere and fell vertically right next to the lug connection for the hot leg of the plug inside the game. The vibration of walking near the game would be enough to shake the washer, trip the GFCI and the washer would end up with just enough gap to not completely short out.

I'm currently replacing every outlet and switch in a 3.5K sq ft home. Installed a GFCI in a bathroom and it did not have power and the 2 load outlets were also out. Turned out the new GFCI was defective and was tripped and could not be reset.

A lot of these new GFCI outlets that you get these days on the bargain racks have a little "mickey mouse" circuit card inside with surface mounted electronics on it that are especially susceptible to damage from voltage transients that might occur with lightning in the general area (for instance). They are made as cheap as possible and prone to fail with any small electrical disturbance that affects them.

It was an Eaton from Lowes the homeowner bought. I was on the job hourly not bid, so it is what it is.

What do you read from the ground braid just inside the door, left side of cabinet to the ground prong on your wall plug?

On my machines(Space Invaders, Mata Hari, Power Play, Evel K) I read 0.3 to 0.4 ohms.

Following this to see what resolves it. I love a good troubleshooting thread.

Try bypassing the EMI filter and take it out of the equation like Mthomasslo mentioned in post #30.

Is this an Arc Fault interrupter by any chance?