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

snipped-for-privacy@panix.com (Scott Dorsey) writes:


So you use a battery in the mike->fiber converter on the performer's belt or hide it in the middle of his back al-la GWB.
On stand-mounted mikes, ditto.
The military makes fiber that's allegely sturdy enough to survive being driven over by a tank, so the average rock group should have to work hard to do it in...
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God, I hate doing that. That now becomes the number one major failure source, the same way it is with wireless packs. And now you have to replace all the batteries before every performance, just in case. Just like wireless packs.

Yes, the military tactical fibre is very commonly used in this application, although most folks today are using the lower cost broadcast connectors instead of the military T-FOCA ones. The military connectors are several hundred bucks a pop which can often exceed the cost of the cable.... some friends at Univision recently spent $30K for only half a mile of tactical cable and Neutrik broadcast connectors (including the cost of the sling to carry the reels on your back). That's a whole lot more than 16-channel Canare snake cable, but probably less than video triax bundles. And it's a lot lighter to carry around. --scott
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snipped-for-privacy@panix.com (Scott Dorsey) writes:

True... but look at the good side; you never run out of tested batteries for your smoke detectors & garage door openers.
If it's Elvis impersonators or similar; you could use a wobble generator like those magnet+coil flashlights you shake to power up. I've also heard of a larger version on railroad cars...

...
A FOAF founded a company that makes fiber converter systems for remote broadcast cameras. Initially they were a hit for golf tournament coverage. It used to be the network had to dispatch multiple semi-trailers with honking big reels storing the miles of $$$$ copper. Now, one small diameter fiber does the job. His market has now spread far beyond golf, I suspect.
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David Lesher wrote:

Sometimes the person is in contact with another current source and is killed by touching a grounded microphoe or instrument, so somone can die if the sysytem is properly installed. A GFI won't detect the current flow to earth from a different source.
There was a recent news story of a pastor dying while baptising someone. A lot of plumbing is now all PVC, so a bad heating element that is shorthed to its casing won't trip the breaker, or blow a fuse. The skin of a water heater is grounded, but the tank may not be.
The man was waist deep (or more) in the water when he picked up the grounded microphone, and couldn't let go.
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Right. The GFI dectects only an imbalance in neutral and hot currents on the device it's protecting.
This means that EVERYTHING on the stage area needs to be on a GFI, and that includes backline. If an amp is popping the GFI, you need to fix it.
Now, I know that outdoor festivals it's very common to defeat GFIs in order to deal with backline equipment that has ground fault issues. I don't have a real problem with this, IF the power system grounds are good enough and the crew is watching out.

Note that he was electrocuted by a circuit which BY LAW needs to be on a GFI, and has been for more than a decade now.
See, in a perfect world, there are no electrical leakage issues. But the ground is there to protect you when things go wrong. And the GFI is there to protect you when the ground goes wrong. It's a belt-and-suspenders thing.
Maybe you'll never need the ground to be there. Probably you'll never need the GFI. But if you SHOULD need it, you'll be really glad you have it. --scott
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Scott Dorsey wrote:

Scott, I still pull green wire with EMT.
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My personal favorite is when no green wire is pulled in the EMT feed to a three phase panel without a neutral. Then another bozo comes along and adds a single phase circuit and terminates the neutral to the ground bar (just like you would in the main panel, right.....)
And then the customer wonders why sparks come out of the conduit joints and employees get tingled when the touch the equipment. Yes, I've seen it more than once.
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Matthew Beasley wrote:

I had a problem at a school. A dead circuit: One end of the conduit had white, black and green wire. The other end was red and blue. Someone had moved and outlet, years ago. They had spliced the wire in the conduit by extending the black wire with red, then tied the white and green together with the blue. No wire nuts or split bolts, just two very loose twists and cheap plastic tape that finally burnt open. After some checking, and old janitor told me that a former teacher had moved it, rather than waiting for the school board to send their electricians.
then there was the time I had a run in with a volunteer fire department. I told them their wiring was substandard. I hit the breaker box with my fist, and sparks flew out of it. I told them that if they didn't have everything repaired within 30 days, I was calling the state to have their certification revoked, and the county to condemn their building. It was bad enough that they were using the building, but they also let a Boy Scout, and a Cub Scout troop use the building, as well.
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A classmate was helping out a friend who'd bought a house. The previous owner was a retired Navy CPO Electrician. Black was ground. White was hot...everywhere...
Within PEPCO [MD/DC area], they use multiple wire cable where green is hot. I saw it once & said "WTF??" to the crew. The guy smiled and sung out:
    Green is Ground,     The world around...         except at PEPCO...
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God bless you! --scott
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On Sep 5, 10:29 am, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

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 http://www.freeinfosociety.com/electronics/schemview.php?id 9 This model is an example of the type of amplifier used in the 60's for everything from bass to organ to guitar and yes, vocals. It was common practice (although not ideal) to run all instruments and mikes off 2 to 4 instrument amplifiers all of which had non-grounded and non- polarized power plugs. Even when you graduated to a real PA system the amplifier's design looked basically the same. Note the primary (mains) circuit of the power supply. No earth ground, no polarization for the plug or accessory socket.
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
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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
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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

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David McCall wrote:

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.
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"VWWall"

** Nonsense.
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.
1950s and early 1960 examples were typically covered in cardboard tubes - usually reddish brown in colour.
Later examples were fitted into plastic sleeves - could be nearly any colour.
...... Phil
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Phil Allison wrote:

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.

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message <snip>

That is why I said earlier to touch the mic with the back of your hand before grabbing or kissing it.
peace dawg
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Please note the word "EVERYTHING" above. Not some of the amps, one of the mixers... everything on stage running from one GFI or another... [Except the drummer, of course, who's likely running on crank, but at least he's not a current source...]
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DC outlets? I've heard tell, but I've never actually seen one. Do you know if you can you still buy DC and steam in New York? DC is great for studios and theater because the lamps don't sing. The problem is, there isn't much other than old resistance dimmers that will work with DC. Have you seen it in other places?
David

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NYC still had DC mains available until about a decade ago, when Con Edison finally managed to install rectifier stacks running off three-phase at the last of the DC customers. Most of them were folks using DC for elevator service.
However, because of the leftover DC infrastructure, you will still see places with DC power panels, operated off a rectifier, and with outlets off the DC panel.

It still turns up in some larger cities with very old infrastructure. Here you're more likely to see DC elevator motors with a motor-generator set to provide the DC for them, but up in Richmond, VA. there is a church with a fancy speed control system on their organ that was originally hooked to DC mains and today is run off a rectifier stack. There are probably a lot of those around. --scott
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