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Re: OT (most likely) strange modem disconnection when using USB drives



On Wed, 03 Oct 2007 03:30:46 +0930
Tim <ignored_mailbox yahoo com au> wrote:


> Isolated PC (grounded), with monitor (grounded), keyboard, mouse, USB
> enclosure, no other connections.  Nothing to tie it to the any other
> equipment, anywhere.  I can't see how this would cause an earth loop to
> the something in the other room.

I don't know enough electrical theory to explain this stuff.  I have seen an
electric meter still running at a  closed-down building with all of the power
shut off at the main breaker box -- we discovered the problem when we got the
next power bill.

> The phone lines a twisted pair of copper to the exchange, all the way,
> still, as far as I'm aware.  I don't think they've updated the wiring
> around here in 40 years.  Grounded at their end, but not at this end.

That's different.  My telephone wiring is also twisted pair and I'm almost
certain that it's grounded on my end.  My FM antenna and the phone wiring are
both grounded to a piece of metal electrical conduit that is, in turn, grounded
to my municipal water service pipe. 

> > Try switching the modem to a different electrical circuit and see if anything
> > changes. 
> 
> Not possible, unfortunately.  Everything's on the same phase.  My only
> choice, which isn't impossible, is to try running it from a battery.

A long extension cord and a friendly neighbour, perhaps?

There are also some weird effects that can be created by hooking devices from
different circuits together.  I know that the electrician here had to do some
fancy stuff to make my air conditioners and the zone valves on my hot water
heating system work properly as they run on different circuits.  It ended up
that there was no easy way to use a single thermostat in the rooms, even though
the devices would never be on at the same time and even though the thermostats
physically switch from "cool" to "heat" so you wouldn't think there would be a
conflict.


-- 
MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com


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