Playing barefoot

[Mick Bailey]

You mention non-conductive rubber soled shoes - good point. Many people don't realize that shoes can be comparatively low-resistance; leather-soled shoes with natural linings such as cellulose fibre, suede or cotton absorb moisture. Black rubber often contains carbon black and can go as low as a few thousand ohms.

[darkfenriz]

The critical question nobody appears to be asking is where the shock is coming from.

Clearly the equipment must be malfunctioning, but if the good insulation practices are followed then there should be no life hazard.

A couple of guidelines that I personally follow:
- double insulation between live parts and secondary circuit
- 1.5kV or more rated transformers
- non-replaceable fuse on L
- no bridging impedances between lines and Earth (e.g. no Y caps) - as is standard in medical equipmnet
- grounding path to carry full fault current

[eschertron]

The critical question nobody appears to be asking is where the shock is coming from.

Clearly the equipment must be malfunctioning, but if the good insulation practices are followed then there should be no life hazard.

A couple of guidelines that I personally follow:
- double insulation between live parts and secondary circuit
- 1.5kV or more rated transformers
- non-replaceable fuse on L
- no bridging impedances between lines and Earth (e.g. no Y caps) - as is standard in medical equipmnet
- grounding path to carry full fault current

The equipment that the player/band brings may not be the source of the malfunction. It can be in the electrical distribution system itself. Poor or nonexistent ground, or hot and neutral reversed. If the band brings ground-fault test equipment, or their own grounding mechanism (earth spikes for an outdoor show) that may help mitigate the dangers.

[darkfenriz]

The equipment that the player/band brings may not be the source of the malfunction. It can be in the electrical distribution system itself. Poor or nonexistent ground, or hot and neutral reversed. If the band brings ground-fault test equipment, or their own grounding mechanism (earth spikes for an outdoor show) that may help mitigate the dangers.

Non-existent grounding or swapping hot with neutral does NOT result in direct exposition to dangerous voltages with properly designed equpment.

[bob p]

there's a lot of older equipment that's still in use, which was properly designed during it's time, which we would not consider to be properly designed today.

IME the biggest risks come from the venue, not from my equipment. My equipment is something that I can control. I can guarantee that my equipment is safe and isn't going to cause a problem if it's connected to a properly configured electrical distribution system. The problem is that there are a lot of venues where the electrical system just isn't up to code. Roadhouse type bars are the worst -- no grounds, hot/neutral swaps, and inadequate circuits to bear the electrical loads. It's as if the wiring was done by the owner's cousin. I can't tell you how many times I've refused to play because the electrical wiring at the site wasn't up to code.

I think it would be challenging to build an amp that meets Class II standards. Almost everything I've seen is Class 0 or Class I.

[rjb]

i didn't see the need to embed a wooden tailpiece with a conductor and wire that to the bridge. to me, grounding the bridge should be sufficient.

I bet it was a purely cosmetic decision- no visible wire to the archtop bridge.

others talked about smart guy friends who would put capacitors and resistors between their bridge and ground on their jacks to prevent electrocution.

That tip has been disseminated by non other than Dan Erlewine...

Guitar Player Repair Guide: How to Set Up, Maintain, and Repair Electrics and Acoustics
https://books.google.com/books?id=zF...0volts&f=false

Wire in parrallel a 220k ohm resistor and a .001 capacitor with a minimum voltage rating of 500 volts....
...it only lets about 40 volts through your strings if a shock is headed your way. The normal string ground still functions too.
However, with this safety device you'll still get it if you touch metal knobs, jacks or guitar cords. You can be safe from volume or tone knob shock if your pots have nylon shafts, such as Fender used to use.

You mention non-conductive rubber soled shoes - good point....
Black rubber often contains carbon black and can go as low as a few thousand ohms.

Thanks for that tip. I had never considered that my black Pro Walkers might kill me- or that Chuck Taylors might be more than a fashion statement.

-rb

[J M Fahey]

You mention non-conductive rubber soled shoes - good point. Many people don't realize that shoes can be comparatively low-resistance; leather-soled shoes with natural linings such as cellulose fibre, suede or cotton absorb moisture. Black rubber often contains carbon black and can go as low as a few thousand ohms.

Leather soles are porous and absorb sweat which is conductive salty water.
To boot leather soles are thin, contact surface is huge and contact pressure is very high (your full weight), the perfect storm recipe.
Not as good a conductor as copper?
You bet, but salty wet pads are good enough for electric chair use

I think it would be challenging to build an amp that meets Class II standards. Almost everything I've seen is Class 0 or Class I.

I think that in principle Guitar amps can not be rated Class II because user is in direct contact with amplifier chassis.
That said, there are *a few* , very high Tech amplifiers, all I saw were actually Italian powered cabinets, which use 2 pin plugs and those weird blues Speakon type power connectors, and are rated Class II or its European equivalent, not sure they meet US standards until these are updated (as European ones were).

Clearly the equipment must be malfunctioning, but if the good insulation practices are followed then there should be no life hazard.

Not necessarily, miswiring an outlet can turn friendly ground intyo a murderous killer.
The example I mentioned involved guys playing through perfectly wired and grounded, as far as they are concerned, tube amplifiers, but plugged into miswired wall outlets or extension cords.

My friend was shocked through the chest and heavily damaged when he touched guitar strings with one hand, and microphone stand with the other.
Sparks flying show this was not a "few mA through a death cap" case but full 110 or 220V mains through excellent metallic conductors:

[bob p]

It'd be a good idea to put one of these in every one of your guitar cases, and chain one of these to every one of your amps.

[g1]

Bob, in case you haven't seen it, there is one dangerous scenario that those testers won't catch. Agree they are still much better than not testing at all.
See the article linked in the sticky here:
http://music-electronics-forum.com/t38464/

[Axtman]

And now would be a good time to remind everyone that vintage Fender amp "convenience" outlets are ALWAYS miswired. I have yet to open up a vintage amp and see them wired correctly. The smaller slot is the "hot" and should have the black wire. The larger slot is "neutral" and should have the white wire. The hot side has a brass screw while the neutral side has a silver looking screw.

If I work on an amp with a two slot convenience outlet I always replace it with a new grounded outlet and wire it correctly.

[eschertron]

Something I discovered a few years ago was a 6' molded plastic three-prong extension cord, clearly factory issue (a reputable US company's insignia stamped on it) where hot and neutral were swapped from end-to-end. No chance of a third party interference - as I said - molded plastic on both connectors. I'm a firm believer now in "anything is possible".

[Enzo]

Many years ago now, a vendor was selling power cords cheap. Might even have been Magic Parts if I recall. When I called for some, they cautioned me that the cords were cheap because they had been made with the colors on the wrong posts. The cords were perfectly useful, but not recommended where anyone might confuse their function by color code. I remember the green/yellow wire was either hot or neutral, and brown was earth. All three were wrong.

[bob p]

Bob, in case you haven't seen it, there is one dangerous scenario that those testers won't catch. Agree they are still much better than not testing at all.
See the article linked in the sticky here:
http://music-electronics-forum.com/t38464/

Thanks for posting that. I was aware of the bootleg ground issue -- I've found it in boxes before. But I wasn't aware of how to use the Non-Contact Voltage Tester to catch the boogleg ground issue that the 3-lamp tester would miss. Thanks for that!

So I guess I have to append my previous recommendation, and say that you need to have both of these in your test kit:

[Axtman]

Many years ago now, a vendor was selling power cords cheap. Might even have been Magic Parts if I recall. When I called for some, they cautioned me that the cords were cheap because they had been made with the colors on the wrong posts. The cords were perfectly useful, but not recommended where anyone might confuse their function by color code. I remember the green/yellow wire was either hot or neutral, and brown was earth. All three were wrong.

Wow! My opinion is that those cords should have been destroyed or at least had the plugs cut off so someone could use the wire. You know that down the road someone is going to misread the colors and hook something up wrong.

BTW, I also make it a policy to replace those hardware store replacement plugs with a new molded plug and wire. There are good industrial replacement plugs, but I don't trust them. I bet someone could make a mint if they started making replacement power cords with red plugs like old Fender amps.

[Leo_Gnardo]

Many years ago now, a vendor was selling power cords cheap. Might even have been Magic Parts if I recall. When I called for some, they cautioned me that the cords were cheap because they had been made with the colors on the wrong posts. The cords were perfectly useful, but not recommended where anyone might confuse their function by color code. I remember the green/yellow wire was either hot or neutral, and brown was earth. All three were wrong.

I remember that, it had to be 15-20 years ago. Magic also got a batch of Fender knobs with dodgy set screws. Lucky for me the very honest phone salesman warned me away from both.