[Jukebox-list] Grounding Issue

[Don Tutt]

Hi All,
So let's look at what is FATAL.
An electrical "shot" like the one most of us have had at some point, 
obviously didn't kill us at the time...... but, it might have.
Just depends.
During my training as a biomedical electronics technician we learned a few 
things about "juice", the body as a volume conductor, and the heart.
A young healthy heart might take a bit of the kind of electrocuting we get 
fussin' with our jukes. You know, poking a finger in here or in there 
and..... WHAP.
As we age, if some small blood vessels in the heart muscle get plugged up 
they can't carry oxygenated blood to their area of the heart muscle. No 
oxygen causes muscle cell death (ischemia) and the small mass of dead cells 
is called an infarct.
Now then.
The sino-atrial node is the heart's pace maker. It automatically generates a 
pulse that travels up the Purkinge fibers (wires) jumps across the 
sino-atrial gap and proceeds up over the top of the heart and back down the 
other side.  This is what normally happens.
Things get interesting when folks get infarcts. They can act as false 
sino-atrial nodes and can cause the heart to beat irregularly. If 
irregularity gets really bad the heart can go into several different types 
of fibrillation. Different things can happen to you depending on the type of 
fibrillation. Mostly you die, sooner than later, without medical help.

Bearing all this in mind we have to consider one more thing.  It has been 
shown that a current of as little as 50 micro amperes across the heart can 
cause interference in the normal electrical activity of the heart. This 
interference can bring on heart  fibrilllation. So when you have both hands 
busy in the juke and one hand is grounded and the other connects with 
something 'hot' you get a current flowing through your chest and likely, 
across your heart.  From this point it is a crap shoot as to whether your 
heart goes into fibrillation.
Most of us have heard the old saw that you never work with both hands inside 
an electical apparatus that may be live.
Working on anything electrical with one hand in your pocket helps reduce the 
chance that your body as a volume conductor will allow a current flow across 
your heart should your working hand make contact with electricity.  That 
said, if the voltage is high enough you're still at great risk of death even 
using one hand.

Of course there is more to the effects of electrocution on the heart, but I 
don't know it to explain it. Reckon I know enough to be damn careful.

..... a few words about FATAL ....     ;-)

Cheers,
Don




----- Original Message ----- 
From: "Ron Rich" <ronnnrich at yahoo.com>
To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
Sent: Friday, May 05, 2006 8:29 AM
Subject: Re: [Jukebox-list] Grounding Issue


>
>  Gary, and All,
>  "117 vac" can also be fatal !   Just "earthing / grounding" an electrical 
> item does NOT necessarily make it any "safer". Ron Rich
>
> Gary Young <gazzyoung_uk at yahoo.co.uk> wrote:
>  Hi, I agree with Ron, but grounding or earthing as we
> call it in the UK, is much more important on UK
> machines as our machines run on 240volts and getting a
> shock from that can be very serious possibly fatal.
> The first thing I always do if buying any jukebox or
> pinball etc is to make sure everything is
> earthed/grounded properly and check the fuses. I have
> seen them jumpered with all sorts, silver paper, paper
> clips etc. Remember fuses are ther for a reason.
>
> Gary
>
>
>
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