You have a defective or otherwise "floating" ground. It could be due to improper wiring, broken ground somewhere, rusty contact terminals somewhere, even a nail through a wire. You really should contact professional help, it really isn't a do-it-yourself job. I'm an electronics professional and I still consult licensed electrical contractors for this kind of thing. Under the right circumstances someone could get electrocuted, even killed in this situation.

Disconnect the games immediately. You should check the voltage between the common/neutral (white) and the ground at the outlet they are plugged into. It should be zero. The voltage between the hot (black) and common should be ~120. The voltage between hot and ground might fluctuate depending on what's loaded to ground. Get an electrician to correct the problem, and install a GFCI for safety before plugging back in.

http://www.zoro.com/g/00000307/k-G5235763?utm_source=Bing&utm_medium=cpc&utm_campaign=PLA
less than $10, this will let you know if the outlets are wired properly

If you are CERTAIN that each and every pinball machine has it's ground plug intact, then the problem is with the house wiring.

The verify the wiring of the pinball machine:

Unplug it.
Set your meter to continuity with your beeper on, if you have one.
Put on lead of the meter on the ground pin on the plug.
Put the other lead on the metal part that you are getting a shock from.

If you get a beep (or 0 ohms) then your ground pin and grounding inside the machine are fine.
Suspect your house wiring, using the "plug" mentioned above.

If you don't get a beep, then the problem is with the grounding inside the pinball machine.

In either case, a floating ground can, and will, cause all kinds of strange things to happen in pinball machines. I also suggest unplugging them immediately until you find the fault.

https://pinside.com/pinball/forum/topic/machines-giving-me-a-shock

Had same problem! Someone had cut off the ground(round)prong off the plug-in.

That's the principle reason for this happening.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Best of luck and hope its a quick fix.

Sometimes the ground prong appears to be intact, but is actually fractured.
Buzz for continuity.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

Keep us posted on what his step dad finds.

Since this question comes up every week:

With the game off, but plugged in, check your incoming wires in the machine (or the service outlet inside the cabinet).

So, meter set on AC:

One probe on WHITE wire, one on green. Voltage (hopefully 0v)? (if 120v WHITE is HOT)

One probe on BLACK, one on green. Voltage (hopefully 120v)? (if 0v, ground is faulty)

One probe on BLACK, one on WHITE. Voltage (hopefully 120v)?

If both incoming wires are brown, the one with the ribbing running down it's length is NEUTRAL/WHITE.

---------

If using the service outlet:

Small slot = HOT
Large slot = NEUTRAL
Ground Pin = GROUND

Domestic_AC_Type_B_USA.jpg

http://www.pinwiki.com/wiki/index.php?title=General#Replacing_a_Grounded_3-Prong_Plug

GroundedPlug.jpg

--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Question...I live in an older house and ZERO of my outlets are grounded. All have 2 prongs only. Why do I not have this issue?

My guess is that all your receptacles are wired correctly and all your games are on a single circuit.

Do realize, that without the grounded outlets, you do not have the safety feature that 3 prong outlets are designed for. If you get a problem that allows voltage to the cab metal, you or someone else could get electrocuted. That's no joke. Get an electrician to run you a proper ground and change those outlets to 3 prong. If your a DIY'er you can do this yourself as well...just make sure you follow the electrical codes for your area and always turn off the breakers when working on electricity.

I understand it's a safety feature, but that probably isn't happening. It's a big house with plaster walls, and literally an outlet every 12 inches along the baseboard. It would be an absolute nightmare of a project, and crazy expensive to have a professional do. I believe the larger appliances/240v circuits are grounded properly, and the bathrooms have GFI outlets...so I guess I was lying when I said zero.

I still live with my parents (I'm 22), and they've been in this house over 30 years with zero problems...and in any case 120 volts hurts, but rarely kills at 20 amps.

If the outlets are on the baseboard, the baseboard comes off, exposing your wiring, making it a much easier job than a new house!

You can install GFCI outlets on ungrounded circuits and still have the GFCI protection.

I use a GFCI extension cord for locations like old bars that don't have grounded circuits when I do service work.

Yup...that would do it. I bet he had a 3 prong to 2 prong adapter on there.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

That is an incorrect statement that can be deadly. A curling iron or hair dryer plugged into a non-GFCI outlet has been cited in thousands of fatal electrocutions.

vvvv

vvvv

I had a Kiss machine that would give a slight shock on the side rails when you would touch it with a bare arm or side of your body. Didn't really feel it when touching the side rails with your hands. I checked everything I could think of until I finally gave up. None of my other pins had the problem.

Then one day the displays and GI started flickering every now and then until it started getting progressively bad as the machine would warm up. I still couldn't figure it out until one day I turned the lights in the room completely off and opened the back box to see some slight sparking coming from the transformer windings. Here I had a borderline short in the transformer windings that would progressively get worse as the machine warmed up. It would arc against the mounting bracket (which is grounded).

I bought a HTF used transformer for it (and anyone who knows the Bally Kiss knows it takes a unique transformer that was only used in a couple Bally pins) and the problem was gone forever. When it comes to electrical issues with pinball machines, it's amazing what you can see in the dark.

Nobody could have guessed that from your first post:

At least all is well now.