See the following:

https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide#post-1945119

https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide

The problem with this is where do you stop? Ground the transformer? Ground the coin door? The power switch? The lock down bar? The side rails? The legs? Anything metal could potentially shock you.

They built these things for 30 years with ungrounded plugs, operated them in some questionable locations through 10's of thousands of plays each, and I've never heard of anyone being seriously or fatally injured.

That said, anything's possible. I understand your concern with young kids playing them. But if your grounding for safety, do you just ground the stuff most likely to shock you or do you ground everything? Do you protect 100% or 80%?

IMO, if you're worried about a potential shock, get one of those single outlet GFCI adapters and plug the machine into that. Full protection and a lot less work.

At the beginning of my career, my service manager was named Gary. When he was a kid he was at a swimming pool and the pinballs weren't wired properly. The pinball on the left had some malfunction where the side rails were connected to hot AC, the pinball on the right, the side rails were connected to ground. A kid with wet skin squeezed between the pinballs and was electrocuted (killed) right in front of Gary.

Because of this experience, anything that came through Gary's shop we would make SURE that every single screw, carriage bolt, metal rail, metal coin door, metal shooting rod frame would be connected to earth ground through a three prong plug.

He'd come by with a meter and check to make sure.

This took some time, but it's not impossible.

So, if it is a concern for you, that is what I'd do. Every single metal thing on the outside of the pinball that is touchable by anyone... connect it to earth ground through a three prong replacement power cord.

Every Bally and Stern I have worked on is grounded throughout. Legs, side rails, coin door, coin door frame pieces, shooter and lock down bar are all connected to the ground. Everything is in the back box as well but that is more for the boards than safety. Better safe...

Like I said. Anything is possible. Combination of swimming pools, concrete floor, wet skin and probably barefooted would certainly be pushing the boundaries of common sense.

If you want to use a 1970 pinball machine in an environment like that, then all bets are off.

The GFCI adapter I suggested should provide all the protection he will ever need. Even crazy scenarios like above.

450 people die every year from falling out of bed. I'm not going to start sleeping on the floor.

I’ve grounded a couple Gottlieb wedgeheads when they’ve come through with bad cords. Only takes an extra 10 minutes if you are changing the cord anyway.

Most EMs I have bought came with seriously bad power cords that needed to be replaced regardless of the 2 or 3 prong question. I put in a 3-prong cord and ground to the transformer frame, but don't generally run ground wires around that didn't exist in the game already.

I noticed a nice kit on the pinside marketplace a while back. I usually make my own grounding mods, but this shop seems to have some nice stuff:

https://pinside.com/pinball/market/shops/1343-the-pinball-scientist/07028-the-electromechanical-em-pinball-grounding-kits-

Grounding to the transformer base does absolutely nothing to protect the player from a potential shock. A ground wire must be added to any metal part that the player might touch, but most importantly, the front door, as it has line voltage on it.

A GFCI outlet trips when it detects a difference in current going out on your hot wire and the current coming in on your neutral conductor. For most household GFCI devices that difference is 6mA. I would not advise trying to recreate this scenario on your own - This could potentially cause a shock hazard. The test button on the GFCI outlet already recreates the exact scenario above. The GFCI test button creates an actual ground fault with a trip current of 6-10mA.

Since we are talking about gfci’s, maybe someone can explain the benefit or disadvantage of hooking up downstream protection for multiple outlets and machines.

Is this an issue only for games on cement? What about carpet or manufactured wood floors?

No. A situation like the one described by PinRetail in reply #4 can happen on any floor, or floating in space. As an example many Gottlieb games have 120 volts just behind the red metal start button on the coin door. The only thing between you and a direct connection to the outlet is a piece of fish paper insulation. All it takes is two games next to eachother with unpolarized plugs, both with worn out fish paper. Then what you might have is one coin door (and possibly lock down bar, rails, etc.) at neutral and the other at 120 volts, depending on how the plugs went into the outlet. Touch both at the same time and you might as well hold both leads of a stripped extension cord. Ask me how I know.

/Mark

I’ll be curious to know if the inevitable sparking at relays and flipper switch contacts will trip the gfci.

It will not.

I'd say the only disadvantage I can think of would be, if you had people playing multiple machines along the same branch and it tripped, all games would shut off not just the one that caused the trip. And you would never know for sure which one caused it until you tested them individually.

I put an earth circuit on every game that I work on. I run the 3 core cable into the machine and put the live and neurals on and terminate the earth into a connector block, affixed to the motor board. From that, I run a separate earth up to the coin door frame and a link off that to the lock down bar. That makes it easy to disconnect should you need to take that board out at some point.

The replay button will get new fishpaper if necessary and I also cut down one of those black rubber tubes that are used on later machine playfield posts and that fits neatly over the end of the replay button end so theres no chance of any metal connection to the 120v line. I also put heat shrink tubing onto the flipper rods for good measure. I've had a few mains shocks over the years and it's not something you forget.

It's a potential issue anywhere.
I was at a friend's house once, and was playing a Williams EM he had. I put my beer down on the floor, by the leg of the adjacent game. It was a SS game which was apparently fully grounded.
While reaching down for my beer, I touched the leg of the grounded machine while still having my other hand on the EM. Apparently, the EM had a hot wire in contact with the door or lockdown bar, and I got a pretty good blast of AC. Had the SS game not been grounded, I may not have felt anything, but it definitely alerted us to the fact that there was an issue with the EM game.

Is that to say that a GFCI outlet will provide safety for a two prong, non-grounded game, as well as a three prong grounded game?

Adding to bdw85's comments...

In the simplest terms: If a device draws draws 1A on the 'Hot' line, you should have 1A returning on the 'Neutral' line. The net is zero (good). If 1A is being drawn on the Hot and 0.97A is being returned on the Neutral - that means 0.03A is going somewhere, and that somewhere could be you. So the GFI's job is to spot that difference and trip (not sure of the trip level but bdw85 mentioned 0.006 to 0.010A). The GFI doesn't care if the 0.03A might be on the safety ground (a good safety ground would prevent the current going thru you tho) or someplace else...it only spots the difference between the hot and neutral and trips regardless.

If you're worried about the GFI outlet test button providing a valid test, you can get a GFI tester, they are not expensive. Might not be a bad idea just as a sanity test, plus it also indicates the outlet is wired correctly.
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Is there a consensus, then, that cfgi receptacles are a good solution for home users ?

me too

GFCI are good, but they are mechanical, and tend to fail after a decade (my electrician buddy says sometimes 5 years)

That's why the building inspector uses an external device to test them, because sometimes the built in TEST button will trigger it, but the test meter won't

Replacing the unpolarized 2 prong cords with safety ground cords, ensures that all your games do not have the Hot on neutral

I can't speak for the majority but here's my opinion:
Yes GFCI receptacles, GFCI adapters or GFCI breakers are an acceptable solution for home owners. I would even say preferable.
If you rely solely on grounding for protection, you need to ground every single metal part that someone may contact. You also must do it to every machine that you own. One ungrounded (I'll get around to grounding it later) machine placed between two grounded machines has the potential to me more dangerous than not grounding any of them, as mentioned in a couple of the posts above.

One adapter for every machine would be ideal, but would get costly if you have a lot of games. GFCI receptacles are good insurance at a reasonable cost.

As far as reliability, You can trust that the GFCI will trip and save you, or you can trust the grounded game will trip the breaker to save you. But you're going to have to trust something to protect you, unless you want to live like Chuck McGill.

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Ie kooky

Yes, good to use. Even if someone did the ground mods - it only takes one 'oops, I missed that part' to have a safety issue.

I agree too - get some GFCI's. But like Vid said, they do tend to fail (maybe not often, but not uncommon to replace one every once in awhile in my house).

What I would do is to get the plug in type as opposed to the GFI that's incorporated into the outlet. Costs more, but easier to swap out if needed. Maybe run a couple of pins off a single GFCI.

Just like old 2 prong guitar amps from the 50s thru early 70s; kids will do anything to avoid the 10 minutes of labor to bring them up to the current safety standard.

They will buy GFCI power strips to bring to gigs, they will install GFCI outlets in their houses, they will bring a carpet to stand on and wrap the mic in cloth tape.

They still will feel a tingle on their lips against the mic, even though the GFCI does not sense enough current to trip

Finally, they will install a 3 prong cord and ground the chassis, like every person has told them to do for the last 50 years....kids

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You can add a grounded IEC cord receptacle to any ancient Marshall, without even drilling any holes

GFCI's are designed for one purpose: to protect people from electrical shock.

Grounding a pinball machine means you are relying on the circuit breaker to protect you. Circuit breakers are designed to protect wires and equipment from overload or short circuits. As a by-product of that, they can supply some protection if the short circuit is through your body. Sometimes. Maybe.

Here's an exert from Salus Engineering International webpage:

"This model can be used to help illustrate the risks of electric shock and circuit breakers. Figure #4 shows the circuit diagram of an unfortunate individual whose body has provided a ground path for a 220VAC source. In this case the current that this individual is drawing will not even be enough to cause the circuit breaker to trip, as a result the current will be continuous. This will be a case of electrocution where not only will the heart normal cycle stop, but internal organs will be heated in a destructive manner.

There is another reason why a circuit breaker tripping will not protect the human body from an electric shock. Even if the current was enough to trip the circuit breaker, circuit breakers normally take a minimum of 1-1/2 cycles to open. That means that the full voltage will contact the body and the resulting full current will still pass through the body, causing a potentially lethal electric shock. Although circuit breakers are important safety devices, they do not provide protection from electric shock".

breakers2 (resized).jpg

Curious as to what brands your friend runs into as this has not been my experience.

Good GFI outlets typically last several decades, the nursing facility I work in still has dozens that were installed in 1994. By state regulation we test them with Woods device for proper tension and external testing device to trip and verify operation every year. And document of course.

You know what a PITA it is to document every single pin in an outlet?

I guess the GFI mechanism does not suffer from wear, since it rarely, if ever, operates. But of course springs might lose their tension and maybe old lubricants get gummed.

I recommend test tripping GFI's once a year for a few times, to see if the mech is still operational. I have some installed in the 90's in perfectly good shape. When in doubt, replace!

The areas I see GFI fail is when they are mounted outside in a box. Even protected that way nature takes its toll.

Cheap ones from the big box store you might wish to avoid, a good Leviton should serve you well.

If in doubt but a hospital grade unit.

Vid's comment has merit. A ground diverts current that potentially would go thru you. That's always a good thing. The way I look at a GFCI is that it provides another level of insurance to help make it 'idiot proof'.

I've grounded an EM ('76 Freedom) and there's a LOT of places that you need to pick up to be 100% covered. Did I ground every nut and bolt? No. Did I do the major hitters (lockdown bar, rails, coin door, etc.)? Yes. So there's always the possibility a screw head I ignored could get energized.

When I ground something, I know there's a solid ground (I'm an electrical engineer but not an electrician, so maybe not to code). If someone else does the work then how do I know it's been done correctly without double checking? And what if I miss something? Or maybe the outlet ground has an issue? We've all seen the 'worst hack' page here on Pinside, not sure I trust everyone to do the grounding mods right. So that's where the GCFI comes in...it doesn't care about the ground path or that BillyBob did a lousy job of grounding.

The bottom line is I'd trust a GFCI for protection more so than people doing ground mods.

Just point of clarification- Breakers are not so much to protect the equipment but to be the weak link in protecting the wiring and are sized as such.

I'm sure he is not encountering any medical grade GFCIs in people's homes

More likely just the Mexican Levitons from home depot

Almost picked up some cheap ones at HF this weekend. Decided to get the good ones, instead.

Or, just don't put your pinball machine on a concrete pad next to a pool.

Also, don't trim your hedges with a lawnmower.

and don't use a 22LR bullet as a fuse.

I know you guys want the laziest fix, but I think a bunch of you are missing the bigger picture.

By correctly wiring your game, you ensure that:

The switch and fuse is on the Hot conductor

Nobody can accidentally reverse the plug in the outlet

All your games are wired identically, so you don't get zapped when touching two at the same time, or touching a basement stanchion

A half century old power cord probably needs to be replaced anyway.

Even if your GFCI has failed, you are still protected

If the switch is OFF, the rest of the game is not still Hot (and thus safe to service)

-

And of course, you can still use your correctly wired game with a GFCI.....

For us common folk…. Alternating current.. goes back and forth… what would be ‘reversing’?

If you plug the cord in backwards, the Hot is now on the neutral side (the neutral becomes fused and switched)

When you touch a properly wired game, at the same time as a reverse wired game, you feel the current - even if one of the games is switched off

From a current point of view, yes, the current goes back and forth through both sides of the outlet. From a voltage point of view, one side is neutral and remains essentially grounded. The other, hot side of the outlet swings from positive voltage to negative voltage, pushing and pulling current through the neutral side.

As vid1900 pointed out, the hot side should go straight to the fuse. Otherwise even if you blow the fuse parts of your game may be hot, just waiting for a neutral finger or screwdriver to conduct through.

I've posted a note on my tool cart: "Hot goes to the fuse." Eventually, I'll remember it.

You got it.

If we flip the power switch to OFF, we want the entire game de-energized

If we blow a fuse, we want the entire game de-energized

Lamp cord ok? Probably the most affordable wire.

Lol, no

Go to Menards, get a 3 prong extention cord (get Black, not orange) for $5, cut off the Female end

You want enough cord to be able to pull the game out from the row, and still be able to reach the receptacle

Read this before you start:

https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide

If you cut the end off an extension cord, the plug will be polarized. If you hook up this plug correctly, it will be of the proper gauge and will ensure that the hot goes to the fuse. This would get you a new cord and be better than original, while still looking quite original.

99/100 the cord is bad and should be replaced.

Vid and I clearly disagree on the importance of a three prong plug on a 1960s vintage game.

Many years ago, I wrote this article for the pinwiki. It discusses polarized plugs and grounding. https://www.pinwiki.com/wiki/index.php?title=EM_Repair#Replacing_a_Power_Cord

I always replace like for like. I don't try to shoehorn a ground in where none existed before, nor do I run a 3 prong plug and ground the transformer (nor do I have any idea what benefit that could possibly have.)

Next to abortion rights, the two prong v three prong power cord is the second most divisive issue facing the country right now.