🚀 go-pugleaf

All I know is that many people I have spoken to while answering technical
support lines have suffered blown modems due to a nearby lightning storm.
eg. 1. It worked and connected 2. There was thunder and lightning nearby 3.
It says 'No dial tone'.
And this happened to my pc - I heard just one spectacular bang the April
before last - I was about a mile and a half from home. The next day I
switched on the pc - dead. Nothing. Having left my diagnostic brain at work,
it didn't dawn on me until a local child said 'Have you seen where the
lightning blew the paving stone into the road?' This was sixty yards down my
street. Result? Modem, motherboard, memory, graphics card, sound card -
every component attached directly to the motherboard was dead. w_tom can say
all he likes about electrical theory, but experience has shown me that
lightning surges down the phone line blow modems up! After my own
experience, I like to tell callers that the modem has acted as a fuse, and
saved the rest of their P.C. - they seem to find this reassuring!

"JAD" <jdemma25@eartink.net> wrote in message
news:If__a.20585$vo2.8017@newsread1.news.atl.earthlink.net...
> so tom  did lightning take out his modem?
>
>
>
> "w_tom" <w_tom1@hotmail.com> wrote in message
> news:3F3C237C.7A74E7E9@hotmail.com...
> > This discussion is cross posted to numerous newsgroups - not
> > just a UK newsgroup.  Concept of breakdown voltages still
> > apply on both sides of the pond.  For example isolation
> > transformer in modem's DAA circuit may provide 2000 volts of
> > galvanic isolation.  However destructive common mode surges
> > are current sources.  That current will increase voltage, as
> > necessary, to turn that transformer or optocoupler into a
> > conductor. Either they provide isolation without damage, or
> > they do not and become damaged as surge passes through.
> > Through seeking what?  Earth ground.
> >
> >   Protector components do not sacrifice themselves to protect
> > electronics.  Either destructive current flows through them or
> > no current flows - no damage.  But again, destructive common
> > mode surges cannot be stopped, blocked, filtered, or
> > absorbed.  As in a flood, the dam will not stop a flood.  A
> > dike will divert the flood, but only if the flood is shunted
> > downstream.  Galvanic isolation works like a dike.  Only
> > effective IF the surge has some other, non-destructive path
> > downstream - to earth ground.  That is what the 'whole house'
> > protector does; shunt the surge downstream to earth.
> >
> >   Appliances already have galvanic isolation.  But again, that
> > internal protection will only be effective IF the surge is
> > earthed before entering a building.  Appliances already have
> > 'dikes' that will be overwhelmed if the surge is not earthed
> > before entering the building.  Just as dikes work for the
> > town.  If flood is not provided a downstream path, then 'dike'
> > is acting like a dam - and is overwhelmed.
> >
> >   There are no sacrificial components in an effective
> > protection system.  Even a thyristor based crowbar circuit is
> > properly sized to shunt without damage.   A common mode
> > transient either does nothing to the optocoupler OR creates a
> > plasma path through that optocoupler.  A direct lightning
> > strike is earthed without damage to transistors or the
> > protector.  Protection is not difficult and performed so often
> > that protector damage is not an option.  No sacrificial
> > components are found or used in an effective protection
> > system.
> >
> > www.ees-group.co.uk/downloads/Secondary%20Effects.pdf
> > An interesting discussion, but where does this apply to
> > anything posted here?  What numbers apply to this discussion?
> >
> >   We know how to protect everything from direct lightning
> > strikes without damage even to the surge protectors.  Moreso,
> > the protection is so inexpensive.  However plug-in protectors
> > ARE expensive and not  effective protection - which is why
> > they don't even claim to provide such protection.
> >
> >   Described in the previous post is how effective protection
> > from direct lightning strikes is implemented - complete with
> > products and where they can be purchased.  Even the
> > www.ees-group.co.uk article does not dispute what was posted.
> > Bottom line is this: a surge protector is only as effective as
> > its earth ground.
> >
> >
> > Nigel Kendrick wrote:
> > > "w_tom" <w_tom1@usa.net> wrote in message
> > > news:dfee1359.0308120333.5a970e26@posting.google.com...
> > > > As soon as a read about 'fusible' components that protect other
> > > components, then I know the poster does not have electrical training.
> > >
> > > Actually, I'm an electronics engineer by training, including 4 years
on
> an
> > > electronics engineering apprenticeship and a total of 6 years as an
> > > electronics design engineer for visual systems for flight simulators.
> > >
> > > > > either have a fusible transformer that 'sacrifices' itself in the
> event
> > > of a surge in order to protect the PC,
> > >
> > > Instead of 'transformer', I should have written 'isolation circuit'.
The
> > > transformer isolation circuit in a modem includes components to damp
> mild
> > > surges - MOVs, gas arrestors, zener / avalanche diodes etc. These will
> fail
> > > in the presence of *massive* surges but will often damp down
potentially
> > > damaging (to the PC) surges to safer levels.
> > >
> > > >   There is no sacrifical component to save electronics - except
where
> > > urban myth replaces electrical knowledge.
> > >
> > > Obviously not seen a crowbar circuit then--but that's off topic :-)
> > >
> > > > In the UK, this is different
> > >
> > > Freeserve is a UK ISP and so it would be safe to assume that all
> discussion
> > > points in this newsgroup should be based on UK conditions
> > >
> > > >   Furthermore the concept of breakdown voltage is totally unknow to
> > > > the poster.
> > > > Even optocouplers have breakdown voltages typically starting at 2000
> > > volts.
> > >
> > > Er, no it isn't but I wasn't specifically referring to breakdown or
> > > flashover between the input and output of the opto isolator - a surge
on
> the
> > > input circuit will damage the opto isolator even if the applied emf is
> > > insufficient to flash over to the output side so, in effect, the opto
> > > isolator has sacrificed itself in order to protect other equipment.
> > >
> > > > Surge damage is easier in UK where even the phone line has no 'whole
> > > house' protector.
> > >
> > > Exactly
> > >
> > > >
> > > >   That claim of EMP induced surges is only another urban myth that
> > > > falls flat on its face when the myth purveryor cannot provide
numbers
> > > > to support that claim.  Appliances have such good internal
protection
> > > > that only the direct strike causes damage.
> > >
> > > You want numbers - OK, read the following article which has data
related
> to
> > > electromagnetic pulse damage caused by lightning.
> > >
> > > www.ees-group.co.uk/downloads/Secondary%20Effects.pdf
> > >
> > > NK
>
>