Discharging CRT anode and capacitors on a VT52 DECscope

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Thu May 27 18:41:01 2004

> One might say there are two stages. One where the current holds the
> heart long enough to kill

That rarely happens, and cannot happen with a CRT anode - you can cut
off blood flow to even the brain (easily the most demanding piece of
the body in this regard) for a second or so with no ill effects. (A
few seconds and you get unconsciousness; a little bit more and you get
brain damage; a bit more and you get death - but something as brief as
the few milliseconds that a CRT jolt lasts cannot, in itself, do
anything bad due to heart stoppage for the duration of the current.)

However - HOWEVER! - it can nevertheless kill, by throwing the heart
into fibrillation (basically, instead of beating regularly, the heart
starts spasming irregularly, the parts desynchronized from one another
and not effective at pumping blood). It doesn't take too much to
induce this state, and once induced, it can _easily_ last long enough
to kill - indeed, it can be difficult to make it stop. I once read a
very interesting article describing sound topological(!!) reasons why
there must exist a shock that can throw the heart into arrhythmic
action of some kind.

Indeed, if I were to get a brief shock in such a way as to run it by my
heart, I would prefer to get a large shock than a middling-small one -
a large shock is more likely to just change the heart's phase than to
throw it into fibrillation. (Of course, I'd still rather get neither!)
Note that the defibrillators that emergency medical techs use to kick a
misbehaving heart into action again basically just deliver a shock.

And of course, getting a jolt of electricity - whether CRT final anode
voltage or PSU filter capacitor voltage or mains voltage or what - is a
bad idea even if it doesn't go anywhere near your heart; such things
induce uncontrolled muscle spasms if they hit motor nerves, and that
can be dangerous in its own right....

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Received on Thu May 27 2004 - 18:41:01 BST