Gang:

I picked up a recent project which will cause my GFI receptacle to trip even when the machine is powered off. It usually trips within 30 minutes of the machine being plugged in - again, even when the machine is off.

Machine in question is a Bally Mata Hari.

When the issue was noted, I started by replacing the power cord and varsitor. I also replaced the rectifier board. The machine runs without issues. MPU gives me all 7 flashes, all solenoids fire, etc. The ground run seems to be intact across all contact points.

I thought that replacing the power train (which was a mess) would resolve the issue, but it hasn't.

There has never been any other occasion prior to the machine being plugged into the circuit that it would trip. If I leave the machine unplugged, the GFI never trips.

I'm stumped - your insight is appreciated!

Ahhhhh...the service outlet - great idea, @LTG!

The wall outlet is fine. Checks out as "wired correctly". The outlet is a newer (<1year) heavy duty GFCI outlet.

Unfortunately, the service outlet is 2 prong and my outlet checkers (I have 2) are 3-prong. Any suggestions on how to validate the wiring at the service outlet? I guess I "could" just disassemble the receptacle and see which wire is being routed to which slot. But even if reverse wired - would that cause the GFI to trip?

It may be relevant to mention that this behavior has persisted even after replacing the power cord and varsitor and the replacement should be correctly wired as per Vid's vid1900 guide. In any event, a photo is attached to provide a visual.

Thanks for the feedback!

20220628_090352 (resized).jpg

Xenon75 I did not change the line filter. I considered it, but didn't as I didn't have one on hand. My understanding of the filter though was that it simply reduced noise/interference. If we believe it will resolve the issue, I can certainly order one.

Dent00 When the machine is unplugged, the GFCI outlet does not trip. I can run other machines (or the vacuum) on that circuit and it does not trip. It ONLY trips when the machine in question is plugged in. Whether or not there is load on the circuit makes no difference. I have a high level of confidence that the outlet is not the problem. Again, GFCI trips even if this machine is OFF, but plugged in.

I think you may be on to something with the ground fault theory. Does that mean I should inspect every inch of ground braid and where it makes contact? You can see in the photo above it does indeed make contact with the line filter. However, there is no ground to the service outlet. (Photo attached).

Wouldn't this only take place in the main cab at or before the transformer? Or do I need to also be inspecting the head (actually, I guess the transformer IS in the head in this machine).

20220628_093622 (resized).jpg

It was a fully molded cord end piece - no cord cap. I'll measure resistance and report back.

twhtalm - this might indeed be the issue - keep in mind I did NOT rewire what's exiting the filter and running to the service outlet. I did go back to vid1900 s guide for replacing power cords and found this -

So, maybe that end of things was reversed wired at the factory. What do we think, should I cut the crimp connectors - flip the wires to a Brown/Black and Blue/White configuration and see what we get?

Here is a photo from Vid's guide which makes me think we have an error made at the factory - I will reverse those two wires exiting the filter headed to the service outlet and report back.

Vid (resized).jpg

Agreed that they are reversed in the photo. I just popped the hood on another Mata Hari and it is wired the same way - Black to Blue & White to Brown.

What are the odds that both of them were mis-wired at the factory?

The plot thickens....

OK, so check out this post from Quench in the guide to changing a power cord:

I have not yet flipped the wires and confirmed that (if I turn the power switch to the "on" position) that I have continuity from the hot side of the plug to A2-J2-6. Likewise, I have continuity from the neutral side of the plug to A2-J2-7.

This makes me believe that things may actually be wired correctly.

It should also be noted that in the photo above from the Vid Guide that the blue wire is exiting the LEFT side of the filter. On my filter, you'll note that the blue wire is exiting from the RIGHT side of the filter - and the mounting orientation of the filter is the same.

Does that have any bearing on the issue?

MattElder So, then am I chasing a phantom by scrutinizing the wiring leaving the filter?

OK, so I have looked at other photos and determined that regardless of which side the blue and brown wires exit the filter - that the overwhelming consensus is that brown goes to black and blue to white...so I can swap those.

The only other thing I can think of is to try to chase down a ground connection gremlin.

In any event, I am learning from you guys - and you sharing your insight is greatly appreciated!

Dent00 I am going to need to look for a ground fault.

Right now, I don't believe cutting the wires exiting the filter and reversing them is going to resolve my issue. Now, that I have confirmed continuity from both sides of the plug all the way back to the correct pins on the rectifier plug (A2-J2), it would appear that things are wired correctly.

OK, here's what's nuts.

The OTHER (second) Mata Hari has always been on this circuit. There has never been an issue with the GFI tripping. When I cracked open the second Mata Hari a few minutes ago to see how it was wired up and saw that it matched the first (project) Mata Hari, I was intrigued by WHY if it was wired the exact same way, it has never tripped the GFI.

Keep in mind that the second Mata Hari was plugged in, but NOT powered on. While I was poking around under the playfield, I touched the ground wire and the GFI tripped. So, when I touched the braid on the second (long-term resident) machine, while it was plugged in, but powered off, the GFI tripped.

Is this another clue?

YeOldPinPlayer Good feedback.

Here is a shot of the resistance from the ground lug on the filter to the ground braid: 0.2.

This is the project machine which was constantly tripping the GFI by simply being plugged in.

Second machine's findings to follow.

machine1 (resized).jpg

Machine number 2 (the long-term resident) actually reads a higher resistance of 0.3

Soooooooo - neither of them are reading zero. Are we close enough to zero, or do I simply have issues with both units?
Machine2 (resized).jpg

This one I can answer immediately - there is NO ground connection to the service outlet on either machine.

Billc479

0.0-0.1

On project machine: 0.4
On long-term resident: 0.1

Yes, and the problem was persistent with the old cord prior to replacement.

OK, so I am in the office today and cannot troubleshoot as quickly today - darn work for getting in the way of important stuff like working on pinball!

I did disconnect the service outlet last night and capped the wires. The GFI held longer than it ever has (maybe an hour) but then did consistently trip it. I went through 3 cycles just to make sure the behavior went unchanged.

Billc479 Will measure this later today.

I do have a spare GFCI receptacle on hand and may even change that as well, if we don't figure this out. However, keep in mind that the other Mata Hari is plugged into the same receptacle and it never trips it.

Quench You made it to the party! Ok, I'll try to do that tonight.

To confirm steps - that means, desoldering my power cord wires from the filter and then tying the black and white power cord wires to the black and white wires currently crimped to the blue and brown wires exiting the filter. Additionally, tying the ground wire to the power cord to the braid in the cabinet.

Sound about right?

Mthomasslo sorry, I wasn't ignoring that suggestion in post 30 - just hadn't gotten there yet!

Seamlesswall

It is not.

Quench Ay, yay, Cap'n! Thanks for confirming! Not having to move the ground (which now, that I think about it totally makes sense) saved me from one more desolder point!

And it's easier then desoldering wires. Since I have a late night at work tonight - I may have to settle with just the extension cord test this evening.

OK, so last night I didn't get home until after 10PM. Rather than take anything apart, I started with the extension cord approach.

Ran an extension cord from the machine to a different GFCI receptacle in the same room. The machine was the only thing plugged into the receptacle. It tripped in under 15 minutes. Machine was never powered "ON", just plugged in and "OFF".

Do we now feel more confident that the issue is definitely rooted in the machine, rather than the receptacle?

Mthomasslo

No interference from the cage. It is not making contact with any wires.

The power switch is indeed grounded.

When I get home this evening, I'll bypass the filter - agreed - it would be the "best problem" to have.

If it DOES end up being transformer related, at least I can take heart in the fact that those are available.

You guys are GOOD!

That detail about double pole versus single pole and its potential to isolate the transformer, would have slipped past me. Yes, the DPST switch is still present.

Look out filter, I'm coming for you!

Today's update:

Last night I bypassed the filter around 7PM. As of this morning, the GFCI has NOT tripped. Again, the receptacle in question was a good quality GFCI outlet installed under 6 months ago.

I would say we have a resolution! Thank you to everyone who helped us get there - YOU guys are what makes Pinside awesome!

It's funny, but cfh remarks in his guides (which collectively, are the pinball "Bible", if you're not familiar with them) that filters going bad is uncommon.

However, here's a perfect example of where "extremely rare" does not mean "never" and one must be thorough and never rule out anything!

G-P-E your contribution was extra special. When I tell you that you have been on my mind and in my prayers - it's not just idle talk. I mean it. There were several times during the course of this thread in which I went to your website to check the values of components as I also rebuilt the solenoid driver board and considered purchasing more line filters. You are truly an asset to pinball - we've missed you and we're in your corner!

I will wait until Monday, but if we go all weekend without it tripping again, I'll mark this topic as "resolved".

It's funny you should say that, Quench - that was my plan exactly for the one in question.

No issues over the long weekend, so going to mark this one as "resolved".

Again, my sincere thanks to everyone who helped figure this one out!