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Hot / Neutral reversed on outlet

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  • Hot / Neutral reversed on outlet

    Because of the nice weather and because my band is doing an outdoor gig soon, my band practiced outdoors at my bandleader's house. I thought I would test the outlet with one of those cheap 3 light outlet testers. My concern would be a lack of ground. Well the tester indicated the hot and neutral reversed. Will using an outlet with this problem be detrimental to equipment?

  • #2
    Originally posted by Axtman View Post
    Because of the nice weather and because my band is doing an outdoor gig soon, my band practiced outdoors at my bandleader's house. I thought I would test the outlet with one of those cheap 3 light outlet testers. My concern would be a lack of ground. Well the tester indicated the hot and neutral reversed. Will using an outlet with this problem be detrimental to equipment?
    If you test an outlet and it shows any incorrect wiring, do NOT use that outlet. Particularly if there is an open "ground" or if the polarity is reversed. This is especially cogent is situations where you are playing outside. There might be some risk to the equipment, but more importantly there could be significant risk to YOU. Electrical safety code is super important because it is almost always results from a forensic investigation.
    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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    • #3
      This^^^^^^^^^^

      Consider the variables running gear on stage in different polarities and possible ground faults, or lifts, or some of the gear is old and has a hot chassis AND is plugged into that inverse polarity. You really don't want your lips touching the mic while you're holding your guitar strings.
      "Take two placebos, works twice as well." Enzo

      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

      "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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      • #4
        Originally posted by Chuck H View Post
        This^^^^^^^^^^

        Consider the variables running gear on stage in different polarities and possible ground faults, or lifts, or some of the gear is old and has a hot chassis AND is plugged into that inverse polarity. You really don't want your lips touching the mic while you're holding your guitar strings.
        I remember years ago, when I first became a member I think, someone posted a really tragic account of a musician who suffered a severe shock during an outdoor show.

        edit* I think it might have been Fahey? I mention that, because think I remember someone translating the account for us.
        If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

        Comment


        • #5
          See for yourself what an extension cord with inverted hot-neutral can do:



          FWIW, the kid survived grabbing guitar strings with one hand, microphone with the other, but only because all of the following coincided in his favour:
          * he was a young strong heart athletic 27 y.o. guy
          * he was kicked away from the microphone stand (nobody dared touch it of course)
          * his Father in law who was present on first row was trained in CPR techniques and could assist him immediately

          * by sheer chance an Ambulance was already parked at the Theatre door to assist some elderly people in the next room Convention center.

          And even so he got a massive burn scar in his heart as if he had suffered a massive stroke, hell have to live with that the next 40 or 50 years of his life.
          Of course, forget demanding Sports, etc.
          Juan Manuel Fahey

          Comment


          • #6
            Originally posted by SoulFetish View Post
            I remember years ago, when I first became a member I think, someone posted a really tragic account of a musician who suffered a severe shock during an outdoor show.

            edit* I think it might have been Fahey? I mention that, because think I remember someone translating the account for us.
            Scottish band Stone The Crows lost their guitarist when he took a shock onstage in 1972. And then there's the legend of the Yardbirds' Keith Relf who supposedly took a plugged-in microphone into the bath and didn't survive. I'm sure there's lots of other tales of woe besides.

            I see Juan already posted the video of Recife's Rocket Boy.

            One more for ya, goes back about 30 years. One of my old friends started up a blues jam at a local pub. He supplied a little PA, speakers on sticks, and a basic backline. This time he brought some ancient amp, with a 2 wire plug. This wasn't one of those supposed "widow makers," amps with AC line going directly to chassis. No it was a regular amp with a "death cap" connecting the AC line to chassis. But this death cap was - shorted! - so plug in one way no problem, other way the chassis is 120V hot. To test for safety he plugged in his guitar and pressed the strings onto the ball of his SM58 mic. Usually, if he saw a little blue spark, he would reverse the polarity switch on the amp, or lacking that, reverse the plug in its socket. But this time, none of that. Sparks shot off the guitar neck as if he was welding, five strings broke and the low E was stuck to some frets. Hmmm, better break out the spare amp! Spare guitar too. Well he made it thru the gig and lived on to get married to a terrific woman, have 3 kids & send 'em off to college. Saw him and his lovely missus last week at a friend's wedding. The stuff you can do, if you don't get killed...
            Last edited by Leo_Gnardo; 07-21-2019, 02:12 AM.
            This isn't the future I signed up for.

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            • #7
              Jeez this is getting dark. But it's a VERY serious subject to be sure. I can personally attest to that because I'VE been hit. My band was playing a dive bar where (apparently) the owner fancied himself a handyman. Some plugs were inverse and some weren't even grounded (though they had the three prong outlets!). I've told this story in greater detail here in the past, but suffice to say it was very much like the video Juan posted and I earned the nickname "Sizzlin' Chuck". I suppose you could have a worse nickname as a guitar player, even though it wasn't for my playing.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

              Comment


              • #8
                Ok I have to ask. Why is polarity not an issue in Europe, where you can plug in anything both ways (the outlets are made like that on purpose ?!)

                Comment


                • #9
                  Justb thinking aloud:

                  1) death caps are never never ever used in Europe while they were all over the place in USA.
                  Notice Peavey/Fender/Randall schematics where the 120V version has them, and exact same model but 220/240V version does not.
                  I guess that alone says something.

                  2) AFAIK UL compliance or registring is voluntary/optional in USA; while SEMKO/DIN/TV/etc. European ones were mandatory in their respective Countries so manufacturers were under confirmed pressure to meet or surpass insulation ratings.

                  And some Countries such as Sweden had NO grounded outlets for general public use because "they have no easy access to Ground".
                  The reason being that in great part of the Country they have permafrost: a frozen underground layer which never ever melts, not even in Summer, so its all but impossible to install grounding rods.

                  I vaguely remember there was also a similar problem to bury people.
                  Juan Manuel Fahey

                  Comment


                  • #10
                    In the UK sockets are polarized. In many areas the house neutral is connected to ground at the distribution board where the mains enters the house. The whole issue of polarity-reversal not only concerns what happens in fault conditions, but increasingly with EMI supression components the equipment has to be connected with the correct polarity in order to prevent high leakage voltages appearing on the ground side of the equipment.

                    A couple of examples - a customer complained of a shock from his lips touching the mic while holding the guitar and using a harmonizer off an SMPS wall-wart adapter. In the UK many devices do not need the ground connected but there's an assumption that in a correctly wired socket the neutral will be at or near ground potential. The wall wart had an integral plastic pin instead of the usual brass ground (earth) pin. This is to activate the shuttered sockets that we have and also ensures correct polarity. The plastic pin had broken off and this prevented the adapter being inserted. A band member spotted that if the adapter was flipped over a screwdriver could be used to open the shutter and allow the adapter to be used. This flipped the polarity and ensured that the singer got a shock. I opened up the adapter and saw that there was a capacitor from the output connected back to the mains neutral. Because the adaptor was flipped this now connected the output via the capacitor to mains live. OK, the impedance of the the capacitor reduced the shock but still not a good situation.

                    The second example was an auto-transformer connected to a USA-made Bogner Shiva. The mains plug was the re-wireable type and the earth screw was loose. In addition, the extension cable was wired in reverse. I measured 80v between the guitar ground and actual ground.

                    Comment


                    • #11
                      Originally posted by J M Fahey View Post
                      I vaguely remember there was also a similar problem to bury people.
                      They got the "Viking funeral" if ranked high enough, sail 'em off in a burning boat. The rest, left to the polar bears.
                      This isn't the future I signed up for.

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                      • #12
                        I must confess that it was only AFTER rehearsal that I noticed the problem. My bass amp rack has a Carvin power distribution / conditioner (think Furman). The unit shows voltage and indicates a presence of ground. While I was bending over to turn off the amp I noticed that the green ground LED was not showing. So dug through my gig bag for my trusty receptacle tester. That's when I noticed the problem. I let our band lead know and she is going to have an electrician look at it as well as other things in her house.

                        We have another practice this Thursday. I am going to insist we use another outlet until the other outlet is rewired. Oh and I am bringing an GFCI extension cord just for added safety.

                        Comment


                        • #13
                          Yikes this is some scary shit!

                          from a US electricians web site:
                          "AFCI protection for kitchen and laundry areas
                          As of 2014, the NEC has added kitchen and laundry areas to the list of areas requiring AFCI protection. This includes all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying not just outlets but also devices found in these rooms."

                          Combo outlets are not terribly expensive
                          https://www.homedepot.com/p/Leviton-...-0KW/206804820

                          Now I've gotta buy one of these
                          Click image for larger version

Name:	Extech CT70.JPG
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                          Extech CT70 $200 or
                          Click image for larger version

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                          Ideal Industries 61-164 $300


                          and test all of my Mom and Dad's hippy wired house...

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                          • #14
                            Not very dramatic, but we played a gig once and the guitarist raised the neck of the guitar, the high E-string touched the mic, and ZZZZZT, a flash of light and the string burnt in half.
                            Education is what you're left with after you have forgotten what you have learned.

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                            • #15
                              Originally posted by Mick Bailey View Post
                              A band member spotted that if the adapter was flipped over a screwdriver could be used to open the shutter and allow the adapter to be used. This flipped the polarity and ensured that the singer got a shock. I opened up the adapter and saw that there was a capacitor from the output connected back to the mains neutral. Because the adaptor was flipped this now connected the output via the capacitor to mains live. OK, the impedance of the the capacitor reduced the shock but still not a good situation.
                              That's exactly what I was wondering - how come this doesn't happen with EU-type plugs? There is a great deal of equipment that has no ground connection (including wall warts) and they can be plugged in both ways, but no shock. Is it somehow designed differently? Mr Fahey mentioned insulation certification, but is there anything else?

                              For instance, this cap you mention sounds a lot like a "death cap". I presume it is of type that can't short, but are they used at all in Europe then?

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