Re: Soon to arrive my HDTV

On Mar 26, 9:57 pm, G-squared <stratu...@[EMAIL PROTECTED]
> wrote:
> OK, a simple question. How do you protect a device that is only
> equipped with a 2 wire power cord? Are we to open the TV and re-
> engineer the power system?
>
> My personal belief is a gadget like a Metal Oxide Varistor  ( MOV ) to
> clamp over-voltage peaks will cover the bulk of problems.

  Why re-engineeer protection that is already inside every TV?  All
appliances contain protection.  Protection that may be overwhelmed by
a surge that seeks earth ground.

  Put an MOV between two AC wire and the MOV does not even see that
surge.  That surge enters a TV to find earth ground outgoing via some
other path - ie coax cable, antenna, or some other conductive path. A
typically destructive surge is not between two AC wires.  Typically
destructive surge is on one or both AC wires and seeking earth ground.

  If a TV has only two wires and no other electrical connection to
earth, then no outgoing path;  no surge protector is just as good as
that MOV.  But materials that conduct static electricity will also
conduct the typically destructive surge.  Those materials include
vinyl floor tiles, carpets, concrete, wall paint, etc.  Incoming on AC
mains; outgoing on what?  Outgoing via the antenna?  Surge has a
destructive path to earth ground via the TV - with or without an MOV
on its power cord.  That MOV does nothing to abate the typically
destructive surge.

  Protection has always been about earthing before surges enter a
building.  Telcos don't install protectors at their equipment.  CO
(connected to overhead wires all over town) will suffer maybe 100
surges during each thunderstorm - and no damage.  CO's locate
protectors where wires enter a building and as close to earth ground
as practicable.   To make that protection even better, the telco
locates electronics up to 50 meters distant from a protector.
Separation between electronics and protector makes better protection.
Better earthing makes better protection.

  What makes a protector (MOV or whatever) effective?  A shorter path
to better earth ground and a much longer separation to electronics.

  Protection is about where surge energy gets dissipated.  An MOV
between two AC wires does not dissipate the typically destructive
surge.  An MOV's job is not to stop or absorb surges.  The MOV's job
is to shunt (clamp, connect, divert) a surge to something that can
absorb that energy.  Earth ground.  Surges must be dissipated
harmlessly in earth.

  Earth a typically destructive surge so that protection inside every
appliance is not overwhelmed. For homeowners, this means one 'whole
house' protector AND all protectors (including telephone and cable TV)
connected short ('less than 10 feet') to a single point earth
ground.   The MOV properly installed connects a surge from each AC
wire to earth ground.  The MOV does not stop or absorb surges.  The
effective MOV connects typically destructive surges harmlessly to what
it wants - earth ground.   An MOV between two AC wires cannot do that.

http://www.harvardrepeater.org/news/lightning.html
> Well I assert, from personal and broadcast experience
> spanning 30 years, that you can design a system that will
> handle *direct lightning strikes* on a routine basis. It takes
> some planning and careful layout, but it's not hard, nor is it
> overly expensive. At WXIA-TV, my other job, we take direct
> lightning strikes nearly every time there's a thunderstorm.
> Our downtime from such strikes is almost non-existant.  The
> last time we went down from a strike, it was due to a strike
> on the power company's lines knocking *them* out, ...
> Since my disasterous strike, I've been campaigning
> vigorously to educate amateurs that you *can* avoid damage
> from direct strikes.  The belief that there's no protection from
> direct strike damage is *myth*. ...
> The keys to effective lightning protection are surprisingly
> simple, and surprisingly less than obvious. Of course you
> *must* have a single point ground system that eliminates all
> ground loops. And you must present a low *impedance* path
> for the energy to go. That's most generally a low *inductance*
> path rather than just a low ohm DC path.