How much/what electrical danger performing on a covered stage during rain?

In a perfect world, all exposed metal should be tied to a non current-carrying grounding buss. Then the neutral can float wherever it wants.

I've worked on a few old time guitar amps. IIRC, some Fender amps included a 'hum' switch that coupled the amp chassis to one side or the other of the line. I forget the value of the cap., but if anyone recalls, it would be interesting to see what sort of currents might pass from the hot side of the line, through the cap., a human body (Mick Jagger's tongue?), and another similar cap. in a second amp to the neutral side.

Perhaps this is why all the British bands came over to the USA. 110V is more survivable than 220V. ;-)

Starting in the 60's I've enjoyed playing guitar and singing in various garage bands. Nothing serious, loads of fun and we even made a bit of money at it. I know this situation well: playing guitar with the fingers of your left (fretting) hand wrapped around the neck and strings and leaning into the mike to belt out the chorus...Suddenly your lips brush against the metal wind screen of the mike and you feel the jolt which hasn't killed you but now tells you that this is going to be one of those "electrical evenings" with one more thing to worry about other than harmonies, lyrics and timing!

Over the decades, I've noticed this phenomenon becoming much less frequent and today it's virtually a non-issue. This of course is due to the fact that nowadays everything is grounded. Even vintage gear can be made safe such that no performer or tech should be in the position of becoming the return path for two conductors that are at significantly different potentials.

But what was the cause of this event? It was actually fairly common. Every musician who played amplified instrument in the 60's and 70's experienced it and very few of the amplifiers involved were actually faulty.

I refer you to the schematic of a Fender Bassman model AA864

Note the .047mfd 600 vdc cap attached to the "ground switch". This allowed you to switch the chassis ground through the capacitor to either the hot or neutral side of the mains. Other amplifiers lacked the switch but still had a cap of similar value hard wired to one side of the mains. In practice, you flipped the switch or unplugged and reversed the "polarity" of the the power cord to the position which gave you the least hum. It is ironic that the "least hum" position was sometimes the one where the cap was connected to the hot side. For this reason or simply because the band couldn't care less about a bit of hum during the quiet passages their was a good chance that one or more chassis ground was actually connected through a cap to the hot side.

Now the reactance of a .047 ufd capacitor at 60 Hz is 56.4 Kohm. If shunted across 117 vac the resulting "leakage current" is 2.074 ma definitely enough to feel as a shock but probably not enough to kill you unless you had other medical issues. In fact it would not trip most GFCIs. Unless you had very sweaty hands and very moist lips, the actual current flowing from one "hot" amp through your body to another "cold" amp would be considerably less especially when the second series connected cap is taken into account. This is probably why most of the aforementioned musicians of the 60's are still alive though perhaps a bit impaired.

So what was the problem? Well consider what the consumer-grade capacitors of that area were made of. Was it mylar or polypropylene or polystyrene? Did Jimi Hendrix use a capo onstage? Well the typical cap of that value and voltage rating was a paper/foil/wax device. If you've ever taken one of these apart (which is easily done), you'll appreciate how low-tech they were and how flimsy was the paper barrier which could short reducing the reactance to ZERO. If you were unlucky enough to be standing on wet ground or lying in a bathtub or brushed up against a genuinely grounded PA system you could be in for a really bad day!

Fortunately what I've described above was a rare event but I sure am happy to use properly grounded gear so that I can concentrate on harmonies, lyrics and timing!

David

================================= .047uf 600V as I recall.

I agree Paul. My other post addresses what you bring up. Sorry I didn't see your post come in while I was typing mine. Interestingly the British Marshall amps and others to my knowledge had no grounding caps. Even back then the mains cords seemed to be grounded. I spent some time in Sweden in the late 60's and met a hospital engineer who absolutely could not believe how comparatively flimsy the US two prong plug was. He thought they should be outlawed!

David

I felt that way the whole time I lived in Germany, and for several years after I returned to the US. A minimal US 3-prong isn't all that wonderful, either.

There has been some consciousness-raising among the designers of US standards plugs since then, but AFAIK it isn't manditory.

Speaking of foil and paper caps. In the late 50s I had the fun time of spending hours cleaning thousands of little bits of gooey wax paper and foil out of the inside of a point to point wired Gibson tube guitar amp. This was the main filter in the power supply and it faild with quite a bang. Good old days? Not always :-)

David

That was probably not a paper cap, but an electrolytic, with considerable voltage across it. When they blew, the remains looked like a chicken had been plucked and the feathers left behind!

They still blow, but most are now in aluminum cans, not a cardboard tube like the older ones.

Scott, I still pull green wire with EMT.

"VWWall"

Electro caps were then and still are now all fitted into aluminium cans, then sealed at the top with a rubber gasket to prevent loss of the volatile electrolyte. The can was connected to the negative terminal of the capacitor and a wire lead welded to the closed end.

Later examples were fitted into plastic sleeves - could be nearly any colour.

...... Phil

Ah, you yer-a-peein' guys are just jealous that we've got such an inexpensive, convenient, universally-recognized plug as the US standard, that's been in service reliably for over a half-century.

Admittedly, the contact interface isn't intended to support large weights, merely to conduct electricity. :-)

But really, do you Brits and other Yurps need a fist-sized plug just so you don't have to remember to keep your thumb out from between the prongs?

Thanks! Rich

Doesn't even need to be that bad! Take a .47 uF cap, and even the impedance at 60 Hz is low enough to allow a good fault current.

You'll see fault currents on some cheap PC power supplies with pi filters on the inputs... the pi filter leakage is high enough to pop the GFI. So what do power supply manufacturers do when people complain about this? They leave off the filtration entirely and spew trash on the power line.

But that is a rant for another day.

--scott

God bless you!

--scott

I got one word for you: NEMA Twist-Locks. Available from 15A on up. They make the Europlug look cheap and flimsy!

--scott

I have in my hands a red, yellow, and blue one. The can is much thinner than the recent electrolytics which use the can as a mount. Hence they created much more mess when they blew. The cardboard tube contributed to the mess.

The accepted sig for ng's is: (2 dashes, space, line return)

You're a goddamned idiot, and you couldn't debate if your life depended on it, twit.

I wouldn't work "a show you have". Your shows are s*it. I have, however made wireless mic systems that pass voice, video and data over VARIOUS bands.

Some are used by LEOs. Some are used on carrier decks.

Do you even know what a diversity receiver is?

You're an idiot. The devices I mentioned are using a proprietary packet model, and it utilizes QAM 256.

You're an idiot.

Thanks for proving the above assertion.

F*ck off, you ten years behind the curve retard.

You could have at least provided ONE link, dingledorf.

"Chairman Of The Most Asinine F*****ts "

Hardly the same category as stage performers.

No performance quality radio mics there at all !!

....... Phil

The ruggedized devices I spoke of have BETTER audio, video and data figures than commercial crap does.

You're a goddamned retard.