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Author Topic: A Shocking Experience  (Read 4842 times)

Chuck Simon

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A Shocking Experience
« on: August 29, 2014, 10:17:48 am »

I had an interesting experience last weekend at a outdoor gig.  Several bands so the usual hurry up set up.  I connected a Whirlwind dual direct box with Jenson transformers on the bass, and within seconds smoke started rising from the box.  I did the dumbest thing I could have done and grabbed the direct box while standing on damp ground.  Wham!  I got hit with a good one!  I "suggested" that the bass player promptly unplug his amp, which he did.  Upon inspection, we found his AC cord was damaged where it connected to the chassis and the hot and ground were touching-120 volts running through the chassis of the amp and the housing of my direct box!  One of their guys fixed the cable and I miced the cab, but I was a little pissed about frying an expensive direct box(and almost being killed). The amazing thing is that later when I tested the direct box it functioned perfectly with just a black mark on the corner of the box.  Hats off to Whirlwind!  I think the smoke must have been the tolex on his cab melting where it came in contact with my direct box.  I guess the only way I could have avoided this incident would have been to check the chassis of the amp with my AC probe before connecting to the amp, but how many of us actually check every amp we work with?  I think I will from now on, at least with bands I don't know.
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John Roberts {JR}

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Re: A Shocking Experience
« Reply #1 on: August 29, 2014, 11:10:15 am »

I've suggested this before but back-line should be plugged into a GFCI protected outlet strip.

Life is precious, even musicians.

JR
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Mike Sokol

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Re: A Shocking Experience
« Reply #2 on: August 29, 2014, 11:12:33 am »

I guess the only way I could have avoided this incident would have been to check the chassis of the amp with my AC probe before connecting to the amp, but how many of us actually check every amp we work with?  I think I will from now on, at least with bands I don't know.

I try to check all unknown stage amps with a NCVT (Non Contact Voltage Tester) such as a Fluke VoltAlert before I plug in anything. And while I often don't have time during festivals for this check, for most worship stages I make it a point to check the backline for any hot chassis, especially if there's a baptismal pool anywhere around. Water and electricity don't mix very well.

A $15 to $25 tester such as a Fluke VoltAlert, Amprobe VP-1000 or Klein NCVT-1 will light and beep from up to a foot way from a guitar amp or mixer with a hot chassis, thus giving you fair warning that something is VERY wrong and potentially deadly. I keep one in the top of my gig bag for just this sort of checking.

If you guys like, I'll get Amprobe to send me some free VP-1000 testers to give away here. I just have to think of a simple contest to make it fair since I can only get around 10 of them for free.
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Mike Sokol
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Tim McCulloch

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Re: A Shocking Experience
« Reply #3 on: August 29, 2014, 11:43:41 am »

If you guys like, I'll get Amprobe to send me some free VP-1000 testers to give away here. I just have to think of a simple contest to make it fair since I can only get around 10 of them for free.

Awards for _best practices_ photos of entertainment electrical safety?  No fair using pictures from manufacturers, etc. these need to be OTJ pics.

Maybe some other things, but I think using these as a way to promote safety, rather than a random drawing, might be beneficial.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

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Re: A Shocking Experience
« Reply #4 on: August 29, 2014, 11:54:54 am »

Awards for _best practices_ photos of entertainment electrical safety?  No fair using pictures from manufacturers, etc. these need to be OTJ pics.

Maybe some other things, but I think using these as a way to promote safety, rather than a random drawing, might be beneficial.

Yes, I hate random drawings simply because I never win. Maybe I'm too random.  ;D

What if all of you send in OTJ pictures showing stage safety and I set up a poll so that everyone can vote on the best ones. Then the top 10 selected each get a free NCVT tester.

Thoughts? 
« Last Edit: August 30, 2014, 11:07:13 am by Mike Sokol »
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Mike Sokol
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Chuck Simon

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Re: A Shocking Experience
« Reply #5 on: August 29, 2014, 12:06:15 pm »

Yeah, I have a Fluke VoltAlert that I bought based on past conversations here.  I think I will be using it more often!
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Mike Sokol

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Re: A Shocking Experience
« Reply #6 on: August 29, 2014, 12:08:10 pm »

The amazing thing is that later when I tested the direct box it functioned perfectly with just a black mark on the corner of the box.  Hats off to Whirlwind!  I think the smoke must have been the tolex on his cab melting where it came in contact with my direct box. 

Can you send a good close-up picture of the DI box with the black mark on the corner? Al Keltz from Whirlwind watches this forum and I'm sure he'll get a big kick out of it.
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Mike Sokol
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Al Keltz

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Re: A Shocking Experience
« Reply #7 on: August 29, 2014, 12:10:22 pm »

We had a church a while back that put an IMP 2 between a powered speaker wired to a Reverse Polarity Bootleg Ground and a Presonus mixer wired to a proper outlet. Blew out the speaker. So they tried another speaker. Blew that out too and this time took the mixer with it. Second time fried the IMP's ground wire too.

So check the ground in the DI. The transformers are probably OK but if you want it checked out, send it in to my attention.

Also, this guy's power cord must have had the ground pin broken off? Bad idea as his bass strings were also at 120 volts!

Glad you're OK, hand to foot shock can be the worst.

- Al
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Mike Sokol

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Re: A Shocking Experience
« Reply #8 on: August 29, 2014, 02:00:20 pm »

Amprobe has graciously agreed to send me 10 of their VP1000SP Non Contact Voltage Testers for a giveaway on this forum. We'll come up with contest rules next week, but even if you already have a NCVT, you can still win one and give it away to a starving soundguy (I'm sure you know one). I like the idea of posting On-the-Job pictures of well laid out and safe stages (and not just the electrical stuff). What do you all think? Run the contest for a month to give everyone a chance to snap a few good pics.
« Last Edit: August 29, 2014, 02:27:05 pm by Mike Sokol »
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Mike Sokol
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g'bye, Dick Rees

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Re: A Shocking Experience
« Reply #9 on: August 29, 2014, 04:47:00 pm »

Oopsie...
« Last Edit: August 29, 2014, 04:53:17 pm by dick rees »
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Re: A Shocking Experience
« Reply #9 on: August 29, 2014, 04:47:00 pm »


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