How a guitarist can be electrocuted through his guitar ? How to prevent it ?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by bojocatkite, Sep 13, 2019.

  1. bojocatkite

    bojocatkite Member

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    I was reading this post from Teleplayer on another TGP thread regarding how much care Terry McInturff takes when wiring his guitars.

    https://www.thegearpage.net/board/index.php?posts/28643968/

    and it never occurred to me that electrocution via guitar could be a problem, how can this happen and how to make sure it doesn't ?
     
  2. Dr.Twang!

    Dr.Twang! Supporting Member

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    Wireless is always an option.....
     
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  3. VaughnC

    VaughnC Supporting Member

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    In the days prior to 3 prong AC cords you had to be careful. Sometimes you'd get 120v difference between a microphone and your guitar and that was a painful experience getting shocked through your lips:eek:. Haven't heard of many deaths but there have been a few...especially when the "death cap" in older style amps would short, which put the amp's chassis at 120v, and you wouldn't know it until your lips touched the mic, or you checked the voltage between your guitar & mic with a voltmeter.

    So, at the very least, if you have an old, 2 prong AC cord amp, replace the cord with a 3 wire version and a 3 prong plug, and clip out the "death cap". But that doesn't guarantee that the AC wiring at the gigging location is proper...but they do sell inexpensive LED testers for checking AC outlets, or bring along a voltmeter, or play wireless.
     
  4. Killed_by_Death

    Killed_by_Death Member

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    It's more to do with the amp really, if the amp chassis has the potential to shock you, it's going to get you, unless you're wireless.
    Even if you're wireless & the amp has an issue like that, you're gonna get it when you touch metal on the amp.

    This is the downside of running a stereo rig, because that can cause a shock hazard, if you're not very careful.
     
  5. pickdropper

    pickdropper Supporting Member

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  6. endorphin

    endorphin Member

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    Also beware of balanced power systems. I use this in my recording studio. basically this is a balanced two phase system with 60-volts on each phase having a peak-to-peak voltage of 120-volts. If you are using a modern amplifier where the neutral and ground are separated and the neutral does not contact the chassis, no issues. But beware of older vintage amplifiers where the neutral prong terminates to the amplifier chassis. You will have 60-volts on the chassis and that is enough to break the resistance of the human skin and cause electrocution when touching a grounded object. Remember this too, always wear shoes with a dielectric component to the soles (rubber/insulated). also, avoiding playing while barefooted would be wise.
     
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  7. Tone_Terrific

    Tone_Terrific Supporting Member

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    I don't see how guitar wiring can either cause or prevent shocks if the strings are grounded.
    Some active pups do not require grounded strings, so they will never become 'hot.'
    Otherwise, your hands are touching chassis ground of the amp, unless precautions are made to isolate signal ground.
    Proper grounding will cause a blown line fuse, at the amp, or in the mains if there is a catastrophic amp failure.
    Likewise, other gear should be grounded.
    Most shocks are not fun, but not lethal.
     
  8. endorphin

    endorphin Member

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    Grounding is not as simple as it seems when the potential for electric shock is involved. Yes, I've been shocked many times when playing, as many of us have. The issue comes in when the chassis becomes energized and the electrical potential rests within the body of the person holding the instrument. At first, there is no issue because you have become the same potential as the chassis through the instrument. If one touches a grounded surface and the path of the current flows through the human heart, then the risk of electrocution is high. Sorry to sound morbid, I don't like writing this stuff like this, but YMMV..........Once! I hope I dont come across as a smart ass, because that is not my intention. It's just that there are inherent risks that exist that we may not realize are present.

    Here are the signs of electrocution:
    1. It hurts, so you will see the person being shocked showing obvious signs of discomfort
    2. The "Let Go Threshold" may be present, this only takes a few milliamps of current to curl the muscles of the hand(s) back into the under part of the wrist. This is exactly what it sounds like, you simply cannot let go during the process of electrocution.
    3. If you see this in someone or are experiencing it yourself (hopefully friends are around), do your best to knock them away or eliminate the energized source. Alot to think about, so reaction through understanding the immediate circumstance is crucial, but certainly be careful if you "pull" them away so you don't experience the same thing.

    Just the other day at a gig, our keyboard player plugged a heavily damaged extension cord into the power source, then plugged a powered monitor into it. Out of my guitar source, I went to plug into the monitor and I got the living hell shocked out of me, and the 1/4" jack physically welded itself to the monitor input jack and simply melted away. If I were holding on to a grounded surface with my other hand, I would not be writing this right now. He felt terrible. BTW, this was an extension cord with no enlarged neutral prong and the ground was cut off. What this did was energize the chassis of the monitor because he had the hot and neutral reversed in the receptacle. Now, you might ask, why didn't the breaker trip? I can tell you with certainty that the ground in this system was compromised. You can't see this unless you either use a meter or physically follow the ground all the way back to the bond at the panel, then follow to the ground rod.

    Sorry to sound morbid, but there is indeed risks that are present.

    Just remember this if you can, avoid a path for current to flow through the center of your body. For example, from one hand to the other, this would cause a path of current through the heart.

    Endorphin.
     
    Last edited: Sep 15, 2019
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  9. musekatcher

    musekatcher Supporting Member

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    I've been bit, and had to intercede someone frozen from the current passing thru strings - had we not been there, he'd not survived. That was in the 80s, and an old-then amp was involved.

    With old amps, I prefer to have someone check and correct any issues with bad design, or worn parts (death cap, etc). The other thing I do, is check for voltage with a multimeter between the guitar and the chassis. I had a nice older Peavey that had a three position power switch - I assume one direction was a reverse polarity or something. Sure enough, one position was shocking me if I didn't have shoes on. I checked, and sure enough, 120v thru my guitar and ground. I painted a skull and crossbones over that position, to warn future owners.

    I use a GFCI with suspect venues or power, when playing on the ground, on an elevated or temporary platform, etc. Venue is just as important as equipment with electrical hazards. I've had near misses with venues too.

    Its true there haven't been many deaths associated, but the potential and consequence is too great to ignore. Be safe.
     
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  10. endorphin

    endorphin Member

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    Great point! GFI's will save your life! The way the GFI works is if 5ma of current is missing between the neutral and hot, then the GFI will trip. This means that current is going someplace else other than through the hot to neutral return. Many don't like using these because of nuisance trips. I wish we were plugged into one the other day!
     
  11. larry1096

    larry1096 Member

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    That's a terrifying story.

    When I did electrical work as a side job, we were rewiring a 440V panel to 480V (it was for a piece of heavy equipment that was a European import) and the master electrician got on the heavy gloves, got out the safety mat and his insulated high voltage tool set. He also brought a 4' section of 2x4 and handed it to me.

    When I asked what the board was for, he said, 'Stand here, and if I groan or grimace, hit me in the chest with that hard enough to land me (pointed four feet away) over there.'

    Found out later he'd been in front of a 480V cabinet when some breakers had vaporized, and spent three days blind in the hospital from metal deposits in his eyes, so he knew what the high voltage, high amperage feeds could do.

    I didn't like doing electrical work... :)

    Larry
     
  12. Timtam

    Timtam Member

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    GFCI - known by different names in different parts of the world, eg RCD = Residual Current Device in Australia. Also subject to different regulations across the world, eg mandatory on domestic and commercial power circuits since 1991 and on light circuits since 2000 in Australia ... but never just assume they're in place.

    https://en.wikipedia.org/wiki/Residual-current_device

    Handy to have an RCD inline in your working extension cable ...
    [​IMG]
     
  13. musekatcher

    musekatcher Supporting Member

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    Heres mine:

    [​IMG]
     
  14. Tone_Terrific

    Tone_Terrific Supporting Member

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    The current will run across your skin not through your heart.
    I'd be dead if that were true.
    You should try some compact inline fuseholder and run it to the bridge from ground.
    There is no other way that voltage can be transferred to the strings.
    Fused at the ma level it might work.
    I don't recall seeing this before, so it's either clever or stupid.o_O
    [​IMG]
     
  15. Killed_by_Death

    Killed_by_Death Member

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    If you're conducting Voltage from one arm to the other, it's going almost straight through your heart.
    This is why clever electricians work with ONE hand in the equipment & not touching anything with the other hand.
    The right arm is generally chosen, because if you get a zap on your LEFT arm down to your feet, it's also traveling through your heart.
     
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  16. Tone_Terrific

    Tone_Terrific Supporting Member

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    Small current through your heart is damaging. It cannot be going through your heart just because it is going arm to arm.
    Putting probes into your heart WILL put current through your heart. I think the frightening stats are based on such evidence not overall conductance which can be localized.
    If you note where defibrillators are deployed, it is on a specific path for best conduction, not across the arms.
     
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  17. Killed_by_Death

    Killed_by_Death Member

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    Another thing some electricians will do is put their arm against the metal box, so that if they get Voltage in their fingers it'll go through their arm & into the box, not down their leg or across their heart.
    Of course the better answer is to be standing on an insulator.
    good boots
     
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  18. endorphin

    endorphin Member

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    The internal impedance of the heart area is about 300 ohms, so the current is going to take the least path of resistance to complete the circuit. The skin being one of the highest, but does differ from wet (sweat) to dry. To beat a dead horse, if your right hand touches an amp chassis that is energized and your right knee touches a grounded surface, or vice versa, the shock will likely stay on the right side of the body and you will survive the shock. Like Killed_By_Death mentioned, the hand behind the back is a normal practice for me and others in the electrical biz. The real danger is when we don't expect it from a leisurely fun day in the band, so it pays to use a GFCI cord like others have posted in this thread. YMMV, but I think this has been a good thread from all involved talking about our experiences and answering the OP's questions and for others to read.
     
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  19. Killed_by_Death

    Killed_by_Death Member

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    My old workmates used to complain about the U.S. electrical system that we used in the refinery, because according to them it was not designed to protect the people.
    In the U.K. their plugs are even fused:

    [​IMG]


    That's a thing about electrical shock or electrocution is complacence. We just get accustomed to using it w/o being careful of it.
     
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