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chris...
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Re: Well, yeah, again, electric shocks from mics !! new [Re: dmills]
      #800166 - 02/01/10 07:13 PM
Quote dmills:

Indeed, anything with a 13A socket on it (with very few specialist exceptions (of which an extension lead is never one)), should have a earth connection.



Right!


Quote:

This is the sort of thing that begets two core cables for garden use:
http://www.maplin.co.uk/Module.aspx?moduleno=13176

Note that a two core cable with a 13A PLUG on one end and a female one of these on the other is totally standard (and safe) as a cable for things like some flymo lawnmowers.



Yep - makes sense.


Quote:

What you should never see is such a cable with a SOCKET on it.




Yep - understood.



Quote:

I would suspect someone of modifying a lawnmower cable, but I suppose anything is possible.




As I said, he has no recollection of modifying this extension - but I'll check again...

Thanks for your help!

Chris


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adamb1026



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #803202 - 13/01/10 01:36 PM
Hey guys,

been a while since I've been on here, thought I would keep you updated.

So far so good! No shocks in any venues...yet! Bought the Maplin plug tester and found one of my 4 way adapters had no earth! . Bit red faced when I saw only two lights

Checked the guitarists plugs and the venues, all of which so far are in good order.

Here's hoping it continues

Thanks again guys for all of your help


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plodsmeade



Joined: 03/01/06
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Hugh Robjohns]
      #834561 - 19/05/10 05:19 PM
Quote Hugh Robjohns:


If one or other of those mains safety earths becomes high resistance or disconnected, then the mains input filtering of the amp or mixer will tend to pull everything connected to the now disconnected earth line up to half mains volts (115V in the UK and Europe).





I'm not sure I fully understand how the 115V float works, in so far as what's going on in the device?

Is it something like the voltage is +/- 115V relative to ground only (giving the device the 230V range in use)?


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Sheriton



Joined: 27/01/03
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Re: Well, yeah, again, electric shocks from mics !! new [Re: plodsmeade]
      #834572 - 19/05/10 06:03 PM
It's usually capacitors connected between the live and neutral and the earth. Without an earth reference, it'll float up to a point halfway between the L and N terminals i.e. 115v.

You can see the same phenomenon on class II equipment like DVD players that employ similar filtering. If you measure the potential of the case with respect to a good earth, it'll be in the region of 115v. It's quite safe to touch as there's no significant amount of current available to do you any damage. If you connect a lot of class II equipment together though, you can sometimes feel a bit of a tingle...

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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: plodsmeade]
      #834602 - 19/05/10 08:39 PM
Quote plodsmeade:

Is it something like the voltage is +/- 115V relative to ground only (giving the device the 230V range in use)?




No. That arrangement would be 'balanced mains' which brings with it a whole host of other issues -- both good and bad.

In general, single phase mains supplies operated as an unbalanced system. The neutral is tied to the earth (ground) and the live carries (in Europe) 130V AC relative to that.

To help get rid of any nasty high frequency rubbish on the supply lines, it is common practice, as Sheriton says, to employ bypass capacitors between the live-earth and neutral-earth. That way, any high frequency rubbish gets passed straight into the earth line and away from the equipment.

However, if the equipment safety earth is missing because of a miswired plug or other fault, or if it is a class II (double isulated) device, then what would have been the earthed point of the capacitor interconnection gets dragged up to half the total voltage across both capacitors -- 115V in Europe.

Again, as Sheriton says, the size of the capacitors and the impedance of the supply lines means that no appreciable current is likely to flow..... but if you have several devices all sitting across the mains, each passing some current, then there can be sufficient to give a nasty tingle if not a lethal belt.

With normal mains-earthed equipment, shocks from the metal work are an obvious and definite indication of a serious fault. With Class II devices, it shouldn't happen, but it can and it doesn't necesarily indicate a fault... but is certainly annoying.

Thankfully, it is easily fixed by providng a proper safety earth and a lot of equipment is designed with this option in mind.

Hugh

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plodsmeade



Joined: 03/01/06
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #834798 - 20/05/10 03:49 PM
thank you both, that seems to make sense.

so the 115V is relative to earth, so touching anything earthed is likely to cause a shock, such as a radiator or earthed casing on another unit, not just the mic-mixer-earth?


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Nathan



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Re: Well, yeah, again, electric shocks from mics !! new [Re: plodsmeade]
      #834883 - 20/05/10 09:24 PM
Quote plodsmeade:



...so the 115V is relative to earth, so touching anything earthed is likely to cause a shock, such as a radiator or earthed casing on another unit, not just the mic-mixer-earth?




No, as the earth conductor is not connected to the supply-earth, only things connected to your equipment or metal casing, guitar bridge, strings, etc will rise to this voltage.

Real problem is if there is a serious live to casing fauly on your gear while the earth conductor is compromised -then it's not uncomfortable, it's lethal!

>

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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: plodsmeade]
      #834927 - 21/05/10 08:15 AM
Quote plodsmeade:

so the 115V is relative to earth




Yes. I think Nathan may have misunerstood what you meant.

Quote:

so touching anything earthed is likely to cause a shock, such as a radiator or earthed casing on another unit, not just the mic-mixer-earth?




Yes. Because your body then forms a circuit between the case which is floating at 115V, real earth, the earthed neutral at the substation and back to the box.

Hugh

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Nathan



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Hugh Robjohns]
      #835224 - 23/05/10 10:10 AM
Yes, I agree Hugh, I think I got the wrong end of the stick there...

>

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Lalala Music



Joined: 26/07/10
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #848774 - 26/07/10 08:42 AM
Ahh the electric shock issue! Have had that a couple of times before. I'm a guitarist and singer for Her Sweet Suicide, and had these shocks a while back. My rig mainly consists of an unearthed POD Live... so you can already figure out where the shocks are coming from. I am merely conducting some form of electricity to the mic by touching the guitar, and well, I'm then getting shocked on my lips. That's one hell of a kiss of death!

Solution: Bought an extension cord which had a third earth prong! All good now!

Cheers,
Patrick

--------------------
Hi my name is Patrick. I run Lalala Music an online music business plan to help musicians create, promote, distribute and perform their music.


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Nathan



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Lalala Music]
      #849270 - 27/07/10 07:24 AM
I take it that you Pod Live is not double insulated, ie it needs its earth connection.

>

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damoore



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Statick]
      #856025 - 24/08/10 01:03 AM
Quote Statick:



so the moral is, i guess, test all the extensions as well, especially if it's venue-owned gear and not your own.




Saw this once in an amusing way. Well, it seems amusing now. Was working late and the cleaners were vacuuming. A cleaner got in the lift and went upstairs but only half her extension cord went with her. She got half a flight up and the cord caught on the doors and the lift came to a shuddering halt. We couldn't get it to go down again so I got the office tool kit and removed the plug so the cord would slide through the doors and the lift would continue to the next floor.

After we retrieved the cleaner and the cord I looked at it intending to reconnect it and thought to check the far end. Turned out the other end was miswired! No idea if the end I had taken apart had been miswired the same way. At that point I refused to put it back together. I was kind of spooked - if I had just gone ahead and connected it up "properly" I would have unwittingly produced a cross-wired extension cable.

Moral is it does matter that the cable is correctly connected at both ends. Just having three random wires make the correct connections is not good enough. That and don't assume the previous guy did it right.


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martin randle
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #950359 - 30/10/11 09:19 PM
This same thing happened to me last night (shock off the mic) all the gear we were using (PA mixer guitar amps keyboards were running off one double socket via extension leads. I only use the same leads and have never experienced this before - however we have never played at this venue before.

my girlfriend came up with a classically simple idea and went to my car and came back 2 minutes later with my rubber floor mats. I stood on these all night and didn't get another shock.

I will get a circuit tester before I play there again.

(The Social Club Witchford Ely Cambs UK)

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TSH-Tim



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #950363 - 30/10/11 09:37 PM
Buy yourself a plug tester (£3.50 from CPC)

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Lighting Hire Surrey


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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: TSH-Tim]
      #950446 - 31/10/11 01:20 PM
Yes -- I would stringly advise NEVER plugging anything into a wall socket until you've tested it with a simple mains-tester plug. I've come across way too any pubs, clubs and conference venues with missing earths and L-N reversals.

Also, once you've tested the socket and you know it is safe, ALWAYS plug the equipment in via RCDs, just to make absolutely sure!

hugh

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Gary_W



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993390 - 18/06/12 01:34 PM
I'd like to thank everyone for the info in this thread - I need to find the culprit of a tingle here.

I've played live twice over the last 3 weeks. At both venues, I've had shocks to the lips. I play guitar and sing, though in this band I'm not singing often.... Just as well. It was a mild tingle at venue #1 and sparks, noise and pain at venue #2..... It was too much to be DC - the culprit felt like a reasonably high potential difference between my guitar bridge and the microphone. Interesting to read here about the float up to 115v as this seems to make sense. This was not 'tongue on a 9v battery' - rather more impressive unless I'm being a complete fairy.... Fortunately our bass player had one of the mic pop shields of the hair bear bunch variety which provided ample insulation (no, I am not suggesting this as a solution to my problem before anyone gets excited but this obviously stopped the issue of sparky lips )

I will double check it tonight, but I actually tested the earth bonding on my amp a few weeks back (I had a friend test it to medical grade standards which tested earth bonding, mains leakage, the works and it's spot on and as an owner of a multimeter I'm no stranger to keeping myself alive!). I may have swapped mains leads but all of my mains leads are in good condition so I'll be surprised if it's that. But multimeter from earth to my guitar bridge will be the first thing I do just to rule out that bit.

One question here - folks are mentioning double insulated equipment potentially having a potential...... On my pedalboard, I have several pedals run from a 9v power supply - I can't see how it can be them (if my guitar earth is indeed good as suspected then 9v to earth is just going to drag the 1700mA supply down isn't it?). I also have a couple of Carl Martin pedals (a Quattro and a chorus). These have 2 core mains going to them and are both double insulated. So could it be one of them?

Can anyone tell me a bit more about this double insulated upping the earth potential thing or have I misunderstood? Obviously I'll test tonight with just amp and guitar and then add the pedalboard back in. I'm hoping for no issues at my end which leads me to external problems (venue / pa / extension leads).

On the two occasions it happened it was 2 different venues and 2 different PA's. One thing that was common was a few extension leads (provided by another band member). So, unless we have 2 dodgy PA's and 2 dodgy venues then the extensions are likely culprits are they not?

Thanks

Gary


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Gary_W



Joined: 18/10/06
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993466 - 18/06/12 07:23 PM
OK, I've tested my gear out and all appears fine.... I have a good earth to my amplifier and this continues on to the bridge of my guitar. With the pedal board in, it adds about 2 ohms of resistance (according to my meter whose tollerence is not great).

In short, I have under 3 ohms between my guitar bridge and the house wiring according to the aforementioned cheapo meter. So it's OK in my opinion but correct me if you disagree

I also tested for AC and DC voltage. Unsurprisingly with a decent earth, there was none.

So if I am properly earthed on the guitar side of things, the posibilities are:-

1. Broken earth in the extension lead supplying my guitar kit
2. Broken earth at two different venues (possible but less likely)
3. Broken earth on two seperate mixers (again less likely)

So favourite culprit is option 1 in my opinion - any advance on that?

Many thanks

Gary


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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Gary_W]
      #993482 - 18/06/12 08:59 PM
My vote is for a dodgy mains extension. Best advice if you want to live is (a) never use someone's else's mains extensions and (b) ALWAYS test every wall socket and mains extension socket with a pukka mains tester before you use them!

It's disturbingly common to find wall sockets with dodgy earths, so please do check. But given the common factor of a mains extension I think you would be well advised to get that checked pronto!

Regarding the double-insulated pedals, they are grounded through the guitar amp, which you have proven is properly grounded when plugged into a decent grounded mains outlet.

To sum up, my advice would be (1) to buy a simple plug-in mains socket tester and use it on every wall socket and mains extension every time you rig your gear; (2) invest in a plug-in RCD unit for your gear--it will save your life should the worst happen with a dodgy earth somewhere; (3) get those mains extensions tested and repaired as a matte of urgency.

Hugh

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Gary_W



Joined: 18/10/06
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993511 - 19/06/12 07:40 AM
Thanks Hugh - I really appreciate the advice. I will invest in a socket tester and ensure I take my own extension lead.

It's clear that my guitar earth is at earth potential (where it should be) and that my zapping here came from something else - at the first gig, I was straight into a socket but this time I was using an extension.

Whilst I can avoid my guitar ground floating up by socket tester + own good extension lead, I can still get in trouble if the mixer has a floaty ground can't I? So we're talking about the scenario where it really is the mic giving the shock, not the mic being the decent earth (as seems to mostly be the case here). So unless I become 'band electrician' I'm still stuffed BECAUSE I've got a good earth on my own kit.....


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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Gary_W]
      #993524 - 19/06/12 09:05 AM
Quote Gary_W:

Whilst I can avoid my guitar ground floating up by socket tester + own good extension lead, I can still get in trouble if the mixer has a floaty ground can't I? So we're talking about the scenario where it really is the mic giving the shock, not the mic being the decent earth (as seems to mostly be the case here). So unless I become 'band electrician' I'm still stuffed BECAUSE I've got a good earth on my own kit.....




Yes, there are two ways of getting electocuted in this kind of situation!

The first is where the mic is properly earthed bu the guitar goes live, and the second is wher the mic goes live but the guitar is earthed. In both cases your body closes the circuit.

The good news is that unless there is a really serious fault somewhere, the mic is unlikely to reach full mains voltage. Worst case is that it might 'float' up to half-mains voltage (115V in the UK) if the PA equipment is ungrounded, and that would be from a relatively high impednace, so while unpleasant it's unlikely to be lethal. But it is an extremely unlikely situation in the first place since all power amps are class 1 devices (afaik) and they would impose a solid safety ground on the PA system anyway.

The only totally safe solution that protects you regardless of where the earth goes missing, is to always power your equipment via a good quality RCD. That way, if some of the mains current from either system ends up going somewhere it shouldn't via you, it will trup the power before it can do any serious damage.

Hugh

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Gary_W



Joined: 18/10/06
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993552 - 19/06/12 12:20 PM
Thanks again, Hugh

With regard to RCD's, it's all very well protecting my equipment (and I'll ensure I do so) but this still won't protect me from a dodgy mixer (for example) that has been brought and set up by someone else will it? As my guitar is well grounded, if my RCD detects current to earth it'll trip out MY RCD. As the offending live part is the microphone here which is coming from a mixer I'm not better off as that will keep going and passing me the juice!!

It's one of those situations where it's a very necessary conversation for a guitar player / bassist as you have both hands on a perfect earth connection. As such, you are at the mercy of other folks equipment / venue wiring more than most band members. You are in the position of being worse off if your kit IS perfectly grounded if someone else's is not!

I think I need a chat....


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Sheriton



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Gary_W]
      #993558 - 19/06/12 01:07 PM
Quote Gary_W:

As my guitar is well grounded, if my RCD detects current to earth it'll trip out MY RCD.




Note quite. Your RCD will only trip if it detects an imbalance between the live and neutral currents flowing through your own kit; it doesn't measure current flowing through the earth connection. So it won't trip if you're getting zapped by someone else's faulty kit. On the plus side, that does give you an indication of where the stray current is coming from - if your RCD hasn't tripped, it's probably not coming from your mains supply.

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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Gary_W]
      #993579 - 19/06/12 02:36 PM
You're right -- if the PA system is live and grounding via your system your RCD won't help because it won't interrupt the ground -- but it might still trip if it senses an imbalance of current on the supply.

If you have any doubts about the PA system, look for the PAT stickers -- ask to see the PAT records. Check if they are running their gear through RCDs... and if in doubt, be careful not to touch anything metallic!

And if you do detect anything that you're not happy about, make sure you get those responsible for the kit to investigate properly.

hugh

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Gary_W



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993659 - 20/06/12 06:33 AM
Thank you both - eBay socket tester is in the post and I will be multimetering the rest of the bands extension leads. Also going to take my DMV to the next venue so as, if anything daft DOES happen I can get a bit more buy-in from everyone..... If it says there is voltage it then makes it a lot more believable vs folks thinking I'm wearing nylon


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Jorge
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993663 - 20/06/12 07:45 AM
I don't know how common this is, either in the US or UK, but the subject of Reverse Polarity Bootleg Ground wiring in venues has been discussed on another forum. RPBG is one possible explanation for electric shocks from mics, and could potentially lead to fatal shocks.

I know nothing about electrical wiring in the UK, but for US 120 v three conductor circuits, a Bootleg Ground is when, if no true ground is available, the outlet neutral is connected to the outlet ground. This in itself is not usually a problem. Occasionally, however, on top of the Bootleg Ground miswiring, the building neutral is mistakenly switched with the building hot (Reverse Polarity). When what is thought to be the building hot and neutral leads are then connected to the outlet hot and neutral leads, respectively, what actually occurs is that the building hot is connected to the outlet neutral and the outlet ground (RPBG). This, unlike simple Reverse Polarity, or a simple Bootleg Ground, can cause the case and ground of devices (eg, mixer chassis, mic, guitar strings) to be at live potential. Not a problem until a person touches both that and an actual ground. Then (and this would happen commonly) the person will get a shock, potentially at high voltage.
The problem is that your simple outlet ground tester will find most faults but completely misses the RPBG configuration. You need in addition a noncontact tester that will identify a hot wire without actual metal to metal contact or access to a true ground. Here is a video that explains a simple procedure to find RPBG wiring. A noncontact tester could also find a high voltage (>90 volts) hot chassis, guitar strings, mic cable or mic.

http://www.youtube.com/watch?v=iLk-6pvSlWg&feature=plcp


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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Jorge]
      #993675 - 20/06/12 08:39 AM
Quote Jorge:

I don't know how common this is, either in the US or UK, but the subject of Reverse Polarity Bootleg Ground wiring in venues has been discussed on another forum.




It's a very scary bodge, but thankfully not likely to happen in the UK. I have heard of similar situations in other countries though!

The reason it is so prevalent in the US is because a lot of buildings are fed with what is, in effect, a balanced 230V mains feed with a centre neutral. Some sockets are then run from one side and centre neutral (giving the 115V supply), while other sockets are run from the other side and neutral. Devices that require a lot of power -- like washing machines and so on -- are often powered from the 240V supply directly.

The centre neutral is normally bonded to earth at some point to make the 115V supplies 'unbalanced' in the conventional way, and hence some electricians have been known to indulge in the lazy practice of using the neutral as a makeshift earth rather than run a proper earth cable to the mains sockets.

However, if things then get confused elsewhere in the building it is possible for the live and neutral wiring to end up being reversed, potentially resulting in equipment cases becoming live relative to a genuine earth (like the water pipes and CH radiators!).

In the UK, because we only have a 240V supply in domestic buildings, and because the IEE wiring regulations are so strict, we can't suffer the RPBG syndrome you describe for the US. It could potentially happen in buildings with 3-phase supplies, but again, the wiring regulations are so strict that it just won't happen.

Quote:

The problem is that your simple outlet ground tester will find most faults but completely misses the RPBG configuration. You need in addition a noncontact tester that will identify a hot wire without actual metal to metal contact or access to a true ground.




Yes... it would be a bit of a worry! For all it's faults, there are many good things about living in the UK!

hugh

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Dave Gate
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993702 - 20/06/12 09:32 AM
Many years ago, before the UK switched to the European standard for three phase colour coding (green for Earth, blue for neutral and brown/black/grey for the three lives) I was working on a show in what had been a reasonably famous venue (no names) where the three phase mains had to be tailed in by an electrician. Who attached the blue live phase cable to the neutral, and the black neutral cable to the live phase that should have had the blue cable.

Oh that was fun when the power went on

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Gear List: reverse only.


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Jorge
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993754 - 20/06/12 02:17 PM
Thank you Hugh for that crystal clear explanation. Yes there are some downsides to the anti-regulatory ideology and/or poor enforcement of regulations that have become so prevalent in the US. The good news is no one I know has ever been electrocuted by an RPBG wiring configuration or anything else. Just to be safe, however, I have just ordered a noncontact tester and will add that to my wall outlet testing routine in the venues we play.


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seablade



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Dave Gate]
      #993757 - 20/06/12 02:19 PM
Quote Dave Gate:

Many years ago, before the UK switched to the European standard for three phase colour coding (green for Earth, blue for neutral and brown/black/grey for the three lives) I was working on a show in what had been a reasonably famous venue (no names) where the three phase mains had to be tailed in by an electrician. Who attached the blue live phase cable to the neutral, and the black neutral cable to the live phase that should have had the blue cable.

Oh that was fun when the power went on




Remind me never to touch UK/EU power. In the US the standard is Green = Ground, White = Neutral, and Red, Blue, Black for the three phases. Would be way to confusing.

I can't think of any place I have ever run across with hot swapped to ground and neutral on the hot for the record, scary thoughts there that that can even exist.

Hugh is correct on the basic wiring for most houses in the US (Commercial buildings tend to have true 3-phase though). But even in houses a fairly standard coloring is used, where there is not usually differentiation between phases, but rather the hot is usually black with neutral white and green ground. For 220v in the US Red and Black are usually hot and White is still Neutral with Green for Ground.

Seablade


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Dave Gate
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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993761 - 20/06/12 03:24 PM
It used to be very confusing here, which is where the offending electrician went wrong. Three phase mains had Earth = green, Neutral = black, Red/Blue/Yellow = 3 x live; but single phase had Earth = green & yellow, Neutral = blue, Live = brown.

This is one area where we can wholeheartedly thank the EU for imposing a standardisation . . .

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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Dave Gate]
      #993859 - 21/06/12 09:21 AM
Three phase power isn't something I get to play with these days, but when I did it was red, blue, and yellow and I think if I was presented with brown, black, gey cables today I'd be scratching my head with them!

The definition of a competent person is someone who knows when they don't know enough, and stands back to let someone better trained take over!

hugh

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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #993871 - 21/06/12 09:47 AM
I was there at the changeover, and had to get my venue's old Red/Blue/Yellow Camlock outlets and cables converted to Brown/Black/Grey Powerloks. But the new colours make more sense, as the earth, neutral and first live phase are in line with what you'd find in a single phase UK mains plug.

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Hugh RobjohnsAdministrator
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Re: Well, yeah, again, electric shocks from mics !! new [Re: Dave Gate]
      #993906 - 21/06/12 11:08 AM
I agree it makes sense in the wider construct -- but red, blue and yellow, all being bright colours, shouted 'live' to me. Brown black and grey are all pretty earthly colours....

hugh

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Re: Well, yeah, again, electric shocks from mics !! [Re: Hugh Robjohns]
      #993908 - 21/06/12 11:13 AM
That sounds like the old UK wiring system (before my time!) where red was live and black was neutral (can't remember what earth was). You still find that in domestic wiring behind the sockets and switches, with the earth usually being an unshielded core (which most sensible people slip a green and yellow sheath over!). If you've ever changed a socket or a lightswitch you'll know what I mean.

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Raphbass



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #997166 - 11/07/12 10:58 AM
On a gig last Saturday, the guitarist plugged into a different socket to the rest of us - there was what felt like a good 100+ voltsAC between his strings and his mic that was going into the PA. When he first mentioned it I thought he meant the common little static "zap" you sometimes get - I didn't realize till I myself touched his strings and the mic at the same time that it was a serious buzz - I remember from messing about with transformers as a kid what 120V AC feels like, this was similar.

I got him to plug into a plugboard on the same wall socket as the rest of us and the problem was solved. Not sure whether I should have informed the venue that there was an issue between two earths in different sockets in the same room - or is this normal?

I assume that for example if they plug in two brass standard lamps or similar, one on each wall socket, that the guy holding both would be getting a good dose of current and if the two lamps came into contact there would be a shower of sparks between them.

I've always assumed that earth is earth is earth - I don't quite get how two earths can be so many volts apart, unless something's gone terribly wrong with the building's wiring. This is a posh modern hotel by the way, not a crumbling third-world establishment (and I've seen a few!).


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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #997170 - 11/07/12 11:08 AM
PS - re colours - yes, brown seems to me the most earthly of all colours, how that got to be "live" totally beats me. And given that a common symptom of colour blindness is to confuse green and brown it seems mental to have the two close together in a mains plug. What was wrong with red for live?


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seablade



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Re: Well, yeah, again, electric shocks from mics !! new [Re: Raphbass]
      #997177 - 11/07/12 11:18 AM
Quote Raphbass:

On a gig last Saturday, the guitarist plugged into a different socket to the rest of us - there was what felt like a good 100+ voltsAC between his strings and his mic that was going into the PA. When he first mentioned it I thought he meant the common little static "zap" you sometimes get - I didn't realize till I myself touched his strings and the mic at the same time that it was a serious buzz - I remember from messing about with transformers as a kid what 120V AC feels like, this was similar.




If it was a true shock from incorrect grounding that indicates two things. First that the socket ground was a much higher impedance than it should be(Bad connection) or missing(No connection). And that there was likely a fault inside of the guitar amp that needs to be checked out.

Quote:


I got him to plug into a plugboard on the same wall socket as the rest of us and the problem was solved. Not sure whether I should have informed the venue that there was an issue between two earths in different sockets in the same room - or is this normal?





Yes they need to be informed.

Quote:


I assume that for example if they plug in two brass standard lamps or similar, one on each wall socket, that the guy holding both would be getting a good dose of current and if the two lamps came into contact there would be a shower of sparks between them.





Not unless there was some VERY bad wiring in the venue, or there is a fault in the lamp attached to the socket with the bad ground.

Seablade


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Re: Well, yeah, again, electric shocks from mics !! new [Re: Raphbass]
      #997195 - 11/07/12 12:08 PM
Quote Raphbass:

PS - re colours - yes, brown seems to me the most earthly of all colours, how that got to be "live" totally beats me. And given that a common symptom of colour blindness is to confuse green and brown it seems mental to have the two close together in a mains plug. What was wrong with red for live?




For domestic use it's supposed to be green and yellow striped. So, for colour-blind people you have a dark colour, a light colour and stripes. Not sure how effective it is, though.

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dmills



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Re: Well, yeah, again, electric shocks from mics !! new [Re: ghc]
      #997316 - 11/07/12 10:30 PM
Red/Green/Black was replaced for flexible cables many years ago precisely because of the problem of red/green colour blindness (Back when appliances commonly came without plugs), a red/green reverse in the plug would leave the case live, and this was in the days before RCDs!

This left us with the interestingly odd situation in that single phase flexible cables were brown/blue/green-yellow, three phase flexible cables were usually brown/black/grey with a blue neutral and the usual striped earth (EU standard).
Fixed installation wiring however was usually red/black/green-yellow for single phase or red/blue/green-yellow/black(neutral) for three phase (Note that blue means different things depending on whether the wiring is a flex(Neutral) or installation(Phase)). Note also that a single phase circuit fed from any phase was usually red/black.....

Anyway all this got harmonised across Europe with the new scheme being brown/blue for single phase circuits, black/brown/grey + blue neutral for three phase, this is the same for both fixed install wiring and flexible circuits. It caused some few problems (and a very few expensive mistakes) when first introduced, but the fact that in a modern install blue has only one possible meaning (neutral) is on aggregate a net win.

The only striped wire in common use for mains voltage is the green/yellow one that is only ever used for earth connections and is two colours precisely so that no matter what colour vision problems you have it is obvious.

That concludes a short history of UK wiring.

Regards, Dan.

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Raphbass



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Re: Well, yeah, again, electric shocks from mics !! new [Re: seablade]
      #998192 - 16/07/12 05:28 PM
Quote seablade:

Quote Raphbass:

On a gig last Saturday, the guitarist plugged into a different socket to the rest of us - there was what felt like a good 100+ voltsAC between his strings and his mic that was going into the PA. When he first mentioned it I thought he meant the common little static "zap" you sometimes get - I didn't realize till I myself touched his strings and the mic at the same time that it was a serious buzz - I remember from messing about with transformers as a kid what 120V AC feels like, this was similar.




If it was a true shock from incorrect grounding that indicates two things. First that the socket ground was a much higher impedance than it should be(Bad connection) or missing(No connection). And that there was likely a fault inside of the guitar amp that needs to be checked out.

Quote:


I got him to plug into a plugboard on the same wall socket as the rest of us and the problem was solved. Not sure whether I should have informed the venue that there was an issue between two earths in different sockets in the same room - or is this normal?





Yes they need to be informed.

Quote:


I assume that for example if they plug in two brass standard lamps or similar, one on each wall socket, that the guy holding both would be getting a good dose of current and if the two lamps came into contact there would be a shower of sparks between them.





Not unless there was some VERY bad wiring in the venue, or there is a fault in the lamp attached to the socket with the bad ground.

Seablade




Well yes there was a comedy moment as I looked at his 20yr-old Fender amp and he sort of took umbrage and said with a dry hint of confrontation "never had a problem before", and he then looked just as implicatingly (if that's a word!) at my mixer which is less than a year old, and PAT tested fairly recently... and there we stood for a few seconds in a stalemate. [Cue soundtrack to "the Good the Bad and the Ugly"]

In retrospect, I feel pretty pathetic that it didn't occur to me to get out the mains tester I have in my kit.

If there's a fault in the mains of one of the circuits, couldn't it render the earth live even without a fault in the gear? Haven't thought it through (and unlikely to bother!) but it seems it can't be a simple reversal of live and neutral as the amp was working fine, and the rogue voltage was a lot less than mains (about half I reckon).

Anyway I've emailed the venue to suggest they should check what's going on in their mains sockets.


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