Got shocked BAD

[bitsandvolts]

Not sure if this was mentioned yet, but whenever I'm doing anything inside an amp that's plugged in (irregardless of whether it's switched on)...

...I have one arm behind my back. The danger really comes from getting zapped in one appendage and having the electricity go to ground through your other appendage (while crossing through your chest)....

[TUBEDUDE]

5 mA is enough to stop a heart. The scary part is, if you get even a small shock, and it occurs on the T wave (while the ventricles are repolarizing) the heart will go into V-fib and without a defibrillator death will result. It's possible to die from a shock you'll barely feel if it occurs during that part of the cardiac cycle. We have been lucky!

[Structo]

Hi Tubedude,

Do you have a resource for that information?
Just curious about the technical aspects of that.

[Cygnus X1]

Some...many of you guys are pros and have to watch your time.
For us hobbyists...
I turn off and discharge, then clip to the areas I want to test (scope or meter), then turn the amp back on.

Helps to have a lot of meters hooked up.
Might as well, they are cheap, and I save the expensive meters for precision measurements.

Last time I shocked myself was working on my gas furnace/AC unit.
Did it twice!
Those motor run caps hold a nice bite and are in areas that are difficult to reach.
Just one brush will get you.

[TUBEDUDE]

Greetings Structo,
I have enjoyed your contributions to this forum over the years.
The information on cardiac physiology and function I received training as a biomedical engineer. As i recall it was presented with the text "Fundamentals of Biomedical Instrumentation" by Brown, as the resource. It's been years since I gave my copy to an aspiring Biomed so i don't remember the authors first name. I'm sure a copy can be found on half.com for a reasonable price.

[Structo]

In the early 80's I attended a trade school for computer repair and maintenance.
Back when computers were huge and you had to go on site to do repairs.

I remember part of the training had to do with high voltage safety.
I don't recall the actual numbers and stuff but I do remember that it didn't take much current at all to kill you.
You just need enough voltage to break down the insulation of your skin (which varies on your body) , to push through your skin then the current to stop your heart.
Then they went on to CPR training, which has changed over the years as well.

Seems like the number they taught us was larger than 5ma but I will bow to data that is newer than 30 years ago.

It always scares me reading on guitar forums where some jack ass will tell his buddies to just stick a screw driver in there and spark those caps to discharge them......or some other just as bad method.

[TUBEDUDE]

Yeah, the impedance of the body is around 2Meg, but if you break the skin barrier it drops to less than 200 Ohms. The maximum leakage current for medical devices is 100 microAmps.
It amazes me also that people will just short a cap. I can imagine what is physically happening to those plates. I never discharge caps with less than a 5k 5W, more if it's a really high voltage left on the cap.

[TUBEDUDE]

Structo, the text was "Introduction to biomedical equipment technology" by Joseph Carr and John Brown. 19-10 says microshock currents of 10 to 100 MICRO Amps may cause VFIB.

[LarryN]

i've taken a few nasty shocks over the years. One of 440vdc off of a transmitter final with the addition of high frequency R.F. The burn mark on my hand took 14 years to dissappear. The first shock was as as a toddler, sticking a knife into a wall outlet. Then as a 10 year old, i was trying to remove a stuck piece of toast from the toaster. But tthe worst, and the one most likely to have killed me was as a 16 year old. i was working on my grandfathers tube receiver. I had removed the steel chassis from the wooden box and had the chassis balance on my thighs, shorts on, and was counting the tube socket pins to find the plate of the 7591 tube when the finger i was using to count the oins made contact with said pin. I have been much more careful since. I suppose a case could be made for having some neurologic damage previous to that misadventure, but I'm pleased to find out if i suffer much more neurologic damage i can become as I.T. professional. J.K. The one handed technique has served me well in the last fourty years and I highly recommend it.

Thumbs up on the toaster/knife method! I once hooked up wires to a slotcar motor plugged into a wall socket and lived to tell about it. A fuse blew, but the house didn't burn down. I also touched the 440vdc on a Super Reverb. Very stimulating!

[Noel Grassy]

You fellows ought to take a big wager to the track or such-like and profit
monetarily from such good fortune! I don't mean to be glib about safety or
any thing so coarse. It's bloody amazing these brushes with death have
been a harsh warning considering our odds in actually dying rather than
being "schooled"!

An associate of mine in Humbolt county (the equivalent to San Joaquin Valley for crops of a stonier and costlier variety) had a tenant who "hot-wired" a shunt across his power pole mounted Xfmr to avoid detection
of an elaborate in-door growing facility by keeping his electric bill from
being flagged by the electric company. That joker should have been a wispy
cinder. He must've felt the same way since he didn't disconnect it before he moved out.

It seems the "Hand of Fate" often steers these otherwise doomed
characters back on the safe path rather than swat their monkey asses into a righteous "dirt nap". What lesson has been taught? Why are they spared?
Are these souls destined to line the streets of Pamplona, Spain as fodder?

Again my comments bear no reflection on the amp tinkerers or skilled electrical journeymen who've posted above. They're directed at the folks
in my example who exhibit what would pass for a "death wish" in any
society. Hopefully we can compare notes in the hereafter and get a plausible answer that doesn't revolve around the Creator's cruel & absurd
sense of humor or a pathological gambling yen.

The electric guitar is the only power tool I can think of that lets the operator complete the grounding through their body. i.e. "String Ground".

Thanks for the tips about skin impedance TubeDude. We as inhabitants of
a planet and solar system that are dependent on a highly electrically charged environment are ill suited to defend ourselves or so I had presumed. Apparently our good fortune is our only insurance on this one
way trip.

My only "Live wire sphincter winker" wasn't from an amp but an old record
player I touched in bare feet after exiting our swimming pool one Summer
when I was about 7 or 8 years old. I came to about twenty feet away from
the turntable. I have no memory of the trip through the air of course just
that primal response to what could only be the offending object that launched me so unceremoniously. Visions of that bastard Redy Kilowatt and his weak
admonitions about flying your kite by overhead power lines had my rapt attention. Needless to say, I neglected sharing my new found knowledge with my Mom or Dad that evening. I thought the thumping I got was enough to "grow on" and a parental haranguing could benefit me not a whit!
I love hearing these near miss tales and the amount of juice some of
you have absorbed is jaw dropping. Thanks for sharing your embarrassment in a public forum. I hope these safety meetings can spare
an aspiring amp jockey a withering "I told you so!" from their significant other or much worse. Cheers mates,

Noel Grassy.

[The New Steve H]

This is why I prefer burning myself. It's hard to burn yourself to death with an amp.

[Cygnus X1]

This is why I prefer burning myself. It's hard to burn yourself to death with an amp.

Dammit Steve you got me again!

Smileys suck here, but good one!
LOL.

[The New Steve H]

Hey...it smells like bacon in here...

[Cygnus X1]

Hey...it smells like bacon in here...

Rush reference...BACON is good.

[TUBEDUDE]

Ah. The old lifepak9 defib with the shock advisory adapter. Noel, as you like stories, ill spin a pair of yarns concerning defibrilators. In the late eighties, a biomed tech in Florida decided his marital difficulties would be solved with a cranial defibrillation. 360 joules later, he transitioned to a lighter sense of being. 360 joules is the amount of energy it takes to launch a 2.2 Lb. baby 360 meters in one second! A member of my shop that was blessed with an apparent room temperature I.Q. decided to see what it felt like to be defibrillated. He waited until everyone left for lunch, spread conductive gel on the sides of his thigh, and discharged 5 joules (the lowest setting) across his leg. What he failed to realize was that low energy doesn't mean low voltage. Even at low settings this is 4kV at several amps , just for a couple of milliseconds. The contraction of his leg muscles swung his leg so hard his knee was sore for 3 weeks and it threw his foot up so hard he broke 3 toes on the bottom of the bench! To quote the wise rabbit "Ehh, what a maroon".