Electric Shocks

[stanton119]

I have quite a complicated set-up and occasionally get electric shocks from anything in the set-up that is metal. I have a mixer in the centre, and attached are as follows:
1. Bass
2. iPod, in dock connected to separate mains supply
3. Laptop, connected to different mains supply and ethernet
4. FX pedal in FX loop of mixer
5. TV, with freeview, ipod, and n64 attached.

The shocks usually occur when im in contact with two or more metal things attached to different parts of the set-up, i.e. bass strings and metal laptop.

What should I do???

[neepheid]

[quote name='stanton119' post='42518' date='Aug 7 2007, 04:16 PM']I have quite a complicated set-up and occasionally get electric shocks from anything in the set-up that is metal. I have a mixer in the centre, and attached are as follows:
1. Bass
2. iPod, in dock connected to separate mains supply
3. Laptop, connected to different mains supply and ethernet
4. FX pedal in FX loop of mixer
5. TV, with freeview, ipod, and n64 attached.

The shocks usually occur when im in contact with two or more metal things attached to different parts of the set-up, i.e. bass strings and metal laptop.

What should I do???[/quote]

Wear rubber gloves?

Seriously though, something is majorly wrong and I think your best bet is to dismantle everything and put it back together bit at a time to see what introduces the shocks. Test each component in isolation also.

[BOD2]

Wow - that is complicated !

This is a tricky one. You shouldn't really mess around with anything that gives you an electric shock but I suspect the only way to resolve this is by a bit of trial and error, which is NOT good.

Do you have an RCD circuit breaker at all ? It would be a good idea to introduce one of these somewhere as that would provide some protection. Check your home fuse box first. If it's a reasonably new fuse box then there may be one built-in. If not then it would be a good idea to buy one, plug it into the wall then plug some of the gear into that.

If the house is very old (or you suspect the wiring might be dodgy at all) then you should get that checked out first.

Next check the mains plugs of all the equipment (where you can open up the mains plug). Ensure that the all the wires in every plug are connected correctly and tightly - especially the earth wire. If you don't know how to do this then have someone who does know check this out. If a plug is moulded on, or built-in to a power supply then you can't check these ones and must assume they're OK, unless they're damaged in some way.

When you say "separate mains supply" is it just a different socket in the same room, or a socket in another room ? If it's in the same room then it should be fed from the same mains circuit, which means it 's effectively the same supply (unless there is strange wiring going on). If it's in another room then the next thing to do would be to feed everything from the same mains circuit - use a large adaptor board or two adaptor boards from a double socket, or two sockets in the same room.

After that I would disconnect everything then build it up slowly again, ensuring there are no unnecessary connections between equipment. Checking that everything works along the way.

I really do NOT want to say "check when you first get a shock" as you build it up but I don't see what else you can do ! If you've got an RCD in place then that should minimise any risk but it's never a good idea to work this way.

[crez5150]

[quote name='stanton119' post='42518' date='Aug 7 2007, 04:16 PM']I have quite a complicated set-up and occasionally get electric shocks from anything in the set-up that is metal. I have a mixer in the centre, and attached are as follows:
1. Bass
2. iPod, in dock connected to separate mains supply
3. Laptop, connected to different mains supply and ethernet
4. FX pedal in FX loop of mixer
5. TV, with freeview, ipod, and n64 attached.

The shocks usually occur when im in contact with two or more metal things attached to different parts of the set-up, i.e. bass strings and metal laptop.

What should I do???[/quote]


Thats some kind of set-up........ Is this for gigs????? or is it your bedroom?

[Alpha-Dave]

[quote name='crez5150' post='42553' date='Aug 7 2007, 05:19 PM']Thats some kind of set-up........ Is this for gigs????? or is it your bedroom?[/quote]


Gigs I'd assume, for me a TV would be particularly useful for the punters to watch when any of us breaks into a solo.

Edited August 7, 2007 by Alpha-Dave

[Beedster]

[quote name='Alpha-Dave' post='42558' date='Aug 7 2007, 05:26 PM']Gigs I'd assume, for me a TV would be particularly useful for the punters to watch when any of us breaks into a solo. [/quote]

Sorry to add this, but our guitarist turned up to a rehearsal a few months looking like death warmed up and said that the guitarist in his old band had died from an electric shock while rehearsing. Much as I do not wish to undermine the expertise of the chaps above, trial and error in such a situation clearly runs the risk of error. I would get someone in who knows what they're doing to check out your kit. The problem is probably simple, however, a simple electrical problem can become a complex and dangerous one when an inexperienced person starts trying to solve/fix it
Chris

[BOD2]

[quote name='Beedster' post='42752' date='Aug 8 2007, 09:19 AM']Sorry to add this, but our guitarist turned up to a rehearsal a few months looking like death warmed up and said that the guitarist in his old band had died from an electric shock while rehearsing. Much as I do not wish to undermine the expertise of the chaps above, trial and error in such a situation clearly runs the risk of error. I would get someone in who knows what they're doing to check out your kit. The problem is probably simple, however, a simple electrical problem can become a complex and dangerous one when an inexperienced person starts trying to solve/fix it
Chris[/quote]

I agree 100% - hence the recommendation for fitting an RCD and exercising caution.

I tried to emphasise that I wasn't in favour of "trial and error" but you have to accept that peope often go ahead and try these things anyway (especially if it's in their own house). That being the case I feel it's better to give some guidelines rtahre than nothing.

But yes you are correct - [b][i]any elecric shock is a serious thing and should be treated with extreme caution[/b][/i]

Always use an RCD and if you are in any doubt then consult someone qualified.

[bass_ferret]

Take it all for PAT Testing. Get a tester that plugs into your sockets (couple of quid from B&Q). I would be very surprised if any of that lot does not have a moulded plug.

[zero9]

It could be dodgy wiring in the place where you practice, or the instrument you're using has a problem with the earth connection.

Check or have the instrument checked (does the problem go away with a different instrument?)

Use a competely different place to test your set-up (not the same house you're currently using).

Hope this helps.

[99ster]

[quote name='Beedster' post='42752' date='Aug 8 2007, 09:19 AM']Sorry to add this, but our guitarist turned up to a rehearsal a few months looking like death warmed up and said that the guitarist in his old band had died from an electric shock while rehearsing. Much as I do not wish to undermine the expertise of the chaps above, trial and error in such a situation clearly runs the risk of error. I would get someone in who knows what they're doing to check out your kit. The problem is probably simple, however, a simple electrical problem can become a complex and dangerous one when an inexperienced person starts trying to solve/fix it
Chris[/quote]

It happens. A good few years ago I remember a young kid getting killed onstage at the 'Green Dragon' in Stratford-upon-Avon (don't know if that's still a music venue?) - a total nightmare. I think his mum started a campaign to try & get all the venues to install circuit breakers, etc.

Wise words Chris.
Electricity is not to be trifled with.

[Bill Fitzmaurice]

[quote name='stanton119' post='42518' date='Aug 7 2007, 11:16 AM']connected to separate mains supply
connected to different mains supply and ethernet[/quote]
That's your problem. Don't do that.

[stanton119]

Thanks for all your advice. Its all in one room. If the mixer may be causing the problem. The instrument doesnt make a difference. The shocks are generally very small thankfully... I will of course put safety first. Thanks everyone.

[stanton119]

Ive done some more investigations:

I plugged in one device at a time to the mixer, and using a multimeter measured the P.D. between the metal laptop case and the 3.5mm jack connecting the laptop to the mixer (the 3.5mm jack is not actually plugged in to the computer):

[url="http://img512.imageshack.us/my.php?image=setup1mj2.jpg"][/url]

Just like above, the PD is 0V and there are no problems. However, when the TV is attached to the mixer the PD rises to 13V to 18V. Attached as follows:
[url="http://img339.imageshack.us/my.php?image=setup2qy7.jpg"][/url]

The PD also rises when the ipod mains adaptor is plugged in. I have no idea why, the same effect is observed when they are attached to the same wall outlet. If the 3.5mm jack to the laptop touches the metal enclosure there are very small sparks between them.

What can I do to eliminate this???

Edited August 9, 2007 by stanton119

[stingrayfan]

Makes me think I should be using the RCD from the lawnmower on ALL my gigs and not just the outside ones...

[Bill Fitzmaurice]

[quote name='stanton119' post='43506' date='Aug 9 2007, 05:07 PM']What can I do to eliminate this???[/quote]
Is your TV also connected to cable? The voltage you're reading indicates more than one ground path is present. Read this: [url="http://www.rane.com/note110.html"]http://www.rane.com/note110.html[/url]

[stanton119]

I dont know if this helps, but i think everything is unbalanced. The TV is not connected to cable. The problem is not affected by the presence of the ethernet cable.

[stanton119]

I think I may have sorted it out:
Using a ground loop isolator i tried connecting item by item every configuration possible, measure the PD each time. The best solution I have found is by placing the ground loop isolator between the mixer and the laptop. There was then not shocks between the laptop case and the cable. However, know there are now sparks between the cable for the bass and the laptop case. Would it help to place ground loop isolators between everything?

[Bill Fitzmaurice]

[quote name='stanton119' post='43891' date='Aug 10 2007, 12:50 PM']I think I may have sorted it out:
Using a ground loop isolator i tried connecting item by item every configuration possible, measure the PD each time. The best solution I have found is by placing the ground loop isolator between the mixer and the laptop. There was then not shocks between the laptop case and the cable. However, know there are now sparks between the cable for the bass and the laptop case. Would it help to place ground loop isolators between everything?[/quote]
Isolators aren't fixing the problem, they're just hiding the symptoms. All of your devices should be grounded together at one single ground point, say a power strip, while any peripherals such as cable or internet connections that are remotely grounded should be transformer isolated.

[BOD2]

I would suspect the tv might be the culprit. A tv isn't generally designed for connection to other audio devices so there may be something inherent in the design that is fine when used on it's own, but causing this problem in this setup.

What output from the tv are you connecting to ? You mention a 3.5 mm jack. Is it the headphones output from the tv ? Does the tv have any RCA phonos (often there are three phonos - yellow for video and red/white for audio) ? If it has phonos have you tried connection to these ? If there are no phonos then you can get a SCART adaptor plug with phonos on the back - then you just need to find a free SCART socket for the adaptor and connect in to that.

[stanton119]

All the devices are connected to one extension lead. Currently I am connecting the TV through the 3.5mm headphone socket, it has RCA sockets but only as an input, Ill experiment with scart to see if I have any success.

[markytbass]

Is your laptop fed direct mains or does it have a transformer. If it has a transformer and is double insulated (there will be a square inside a square on the transformer if it is). We had a problem at work where if you leant on the radiator whilst using the laptop you would get a shock (not big more like a static discharge). We all used double insulated transformers which we had upgraded to ones with an earth. This solved the problem, you may find that some static is finding its way to earth from your laptop via you and your srtings. This is a warning sign that much bigger voltages would probably go the same way. If you aren't using an RCD I would get one very soon.

[stanton119]

[quote name='markytbass' post='44613' date='Aug 12 2007, 09:30 PM']Is your laptop fed direct mains or does it have a transformer. If it has a transformer and is double insulated (there will be a square inside a square on the transformer if it is). We had a problem at work where if you leant on the radiator whilst using the laptop you would get a shock (not big more like a static discharge). We all used double insulated transformers which we had upgraded to ones with an earth. This solved the problem, you may find that some static is finding its way to earth from your laptop via you and your srtings. This is a warning sign that much bigger voltages would probably go the same way. If you aren't using an RCD I would get one very soon.[/quote]


Nearly everything is double insulated rather than earth. The radiator problem has also occurred to me. Even when I used to have bass direct to amp. If I touched the strings and the radiator I would get a small shock as you have described.

[Bill Fitzmaurice]

[quote name='stanton119' post='44626' date='Aug 12 2007, 05:25 PM']Even when I used to have bass direct to amp. If I touched the strings and the radiator I would get a small shock as you have described.[/quote]
This is where a GFCI outlet protects you. Your strings are grounded, but not perfectly so, as there is resistance in all of that wire that connects your bass to your amp, and then your amp to the outlet, and finally the outlet to the street mains panel. There can be quite a bit of resistance in that wire, while alternate paths to ground, such as heating systems and water pipes, or God forbid standing on damp earth or concrete floors with no shoes on, may have considerably less resistance. Electricity always takes the path of least resistance, and in cases such as described that path is you. GFCI outlets sense when current is flowing through pathways other than those intended and shut it off.

[KiwiMike]

[quote name='Bill Fitzmaurice' post='44809' date='Aug 14 2007, 01:05 AM']This is where a GFCI outlet protects you. Your strings are grounded, but not perfectly so, as there is resistance in all of that wire that connects your bass to your amp, and then your amp to the outlet, and finally the outlet to the street mains panel. There can be quite a bit of resistance in that wire, while alternate paths to ground, such as heating systems and water pipes, or God forbid standing on damp earth or concrete floors with no shoes on, may have considerably less resistance. Electricity always takes the path of least resistance, and in cases such as described that path is you. GFCI outlets sense when current is flowing through pathways other than those intended and shut it off.[/quote]

It sounds like there could be a bad capacitor in your amp, if you are getting shocks through the strings on your bass.
Often the leakage current is not high enough to trip an RCD, or because the transformer in the amp isolates the power supply from the Mains earth.

[Kev]

problem i have

when i am playin bass, if i hold my strings, and touch somethin metal on my laptop, i get a shock...