This discussion reminded me of a situation here, a few years back: The
power company replaced the wires from my house to the pole, and a few
months later, I happened to touch the metal pipe through which the wires ran
to my meter in the cellar. ZAP! The pipe had never been attached to the
meter box or my fuse/breaker box, both of which were grounded (after I
grounded them - NOTHING was grounded when I moved in here!) ... Anyway, I
called the company to have the thing repaired, as it was obvious that the
live conductor was touching the pipe at the top. They sent Vern & Ernest, I
swear. Even after I demonstrated the problem by lighting-up a 100W bulb
between the pipe and a ground, one of the guys grabbed both pieces of metal
& ZAPPED himself for proof! "Oh yeah, that's live." I guess he was
accustomed to 120volts AC!
----- Original Message -----
From: "Barry Kasindorf" <[email protected]>
To: "Antique Phonograph List" <[email protected]>
Sent: Friday, February 17, 2012 1:43 PM
Subject: Re: [Phono-L] Does anyone know how to make a Jones Motrola _safe_?
Very true. The question was SAFETY. I hate having 3 wire plugs on antique
electronics. You can easily put a polarized plug on a piece of zipcord and
get the ends right and be safe as well. I like the idea of making
something SAFE without changing the item at all.
-Barry
On 2/17/2012 12:25 PM, Bruce wrote:
Barry, the shock hazard model during HiPot testing development assumes
all
external metallic surfaces on a product are always at the same potential.
That is why we are only required to test against the product ground
through
an alligator clamp to the chassis or through the ground terminal of the 3
wire AC input. The shock hazard model we care about is a ground path
through
the body past the heart. You could be standing on a concrete floor
barefoot
or touching a cold water pipe with your other arm.
I submit to you that I could connect any ungrounded electrical device
through my isolation transformer, float it up to 1500VAC (the isolation
voltage of my isolation transformer) and invite you to touch it and
depending on your resistance to ground, you will definitely feel it. It
will
not be much current, and it may not kill you but it will wake you up
faster
than a few cups of coffee.
_______________________________________________
Phono-L mailing list
http://phono-l.org
