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Scott-Tech 11-07-2011 11:46 AM

Possible Ground Fault Without an Intended Ground Path?
Good day:

I'm not a licensed electrician. I work on slot machines. I repair board level electronic parts. I really need to ask some professionals, such as your good selves, about a possible hazard. After being shocked a few of times, I don't want it to happen again, and I don't want anyone else to get a 230VAC wake up call. I was working on installing slots on a luxury cruise ship last year in Genoa Italy. I had all the slots plugged in and was testing them, when I touched two at once, I screamed accordingly. I went along the row of slots to find which slot was the shocker. I used my multi-meter not my hands BTW. At first I thought the problem was with the machine. After a wake up call, I tracked the problem to be with the outlet. I was in a hurry, so I just used another outlet, and all seemed fine. Shockingly not the case, I found another enlightening outlet on another group of machines. I couldn't test all the machines, as they are not all covered in metal, some of them have a lot of plastic on the outside. There where a series of outlets on this row of slots I had to work around. I was told a few weeks later, after I left, that another outlet had been detected where I already tested for the hazard. This was in dry dock before the ships sail, and the bad outlet problem continues to happen after it sailed. I think the ships electricians have done little to amend the problem. It would still be really dangerous to plug anything into those outlets today. I had heard that this was originally a 110VAC system, and they converted it to 230. The machines to this day are having electrically related problems, like losing their static memory. Some of them are rebooting, and not because of the internal components. I had the Casino Manager install some UPS, to see if it would help, and it did, but only marginally. They aren't continuous UPS. I didn't have any test equipment, so I was never able to investigate this, and I think I would of been in trouble for doing so.
So, I am asking in all sincerity; what could be the cause of this shock hazard? What would you do to troubleshoot the problem? I don't think the ships electricians have sufficiently resolved this, and would really appreciate your opinions.

Thank you, and kind regards:

AllanJ 11-08-2011 06:33 AM

Do the machines have three prong plugs and are all of the receptacles properly grounded? This should be enough to prevent shocks.

Holding the machine's plug in your hand, do a resistance check from each prong to exposed metal on the machine. Should you get less than infinity for either hot or neutral prong then that machine has a ground fault and should not be used. Or if you test tghe machine using a GFCI protected receptacle and the GFCI trips then the machine has a ground fault.

For two prong plug machines you can take a long bare 12 gauge wire and daisy chain it from one machine to the next, attaching it using a screw that penetrates to the metal chassis of the machine. Connect both ends to known grounds. (For a non-public environment such as for home stereo components we can omit the redundancy and connect just one end to a known ground.)

You can also do voltage checks from hot to neutral, neutral to ground, and hot to ground in various receptacles. You should restrict usage of the machines to correctly wired receptacles unless the ship owners are willing to accept responsibility for machine failures.

jbfan 11-08-2011 08:28 AM

Are the machines rated for 240 volts?

If not, then you would be burning up power supplies on the machine.

Sounds like it could be a loose neutral on a MWBC that is giving problems.

Wityout the cooperation of the electricians, you really have no way to know.

Just don't touch 2 machines at once.

Scott-Tech 11-08-2011 10:47 AM


Yes all of the machines are rated for both 120, and 240. They all have self switching PSU's. So, nothing is getting blown in that sense, however I have prematurely lost some LCD PSU's, not sure that I can blame that on the power or not, at this point. Thank you for your responses, I was looking for such ammunition. Everything coming out of that breaker box acts flaky, like an inconsistent or loose ground. Which would explain the problems I have been having with the slot machines, such as static memory errors, and rebooting slots. You both are right; without the cooperation of the ships staff, there isn't much I can do. I really hope the ship does something about it before someone gets hurt. Hopefully no-one with a pacemaker tries to get up at the wrong time. I have to do an installation on it's sister ship beginning next year, and should I run into this again, I'll raise fury till they fix it, or kick me out. Do you think some isolation transformers would help, or make the problem worse?

Thank you, and kind regards:

Anti-wingnut 11-08-2011 11:50 AM


Originally Posted by Scott-Tech (Post 765807)
So, I am asking in all sincerity; what could be the cause of this shock hazard?

Lack of paragraphs?

Scott-Tech 11-08-2011 01:15 PM


Okay, I'll work on my grammar.

Kind regards:

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