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

Tim:
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.

Frank Cox:
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.

My field's more electronics engineering than electrician, the two don't
quite cover each other. I've seen similar issues when I tried to get
the meter to stop spinning on our house, one day. I went around
unplugging everything, turning off switches in the meter box, pulling
fuses. Eventually worked out that the air conditioner controller always
drew some small amount of current, but enough to make the disc spin
around. Now we have one of them new-fangled digital meters, without any
wheels to watch. :-(

I suspect one of the neighbours was doing something dodgy with the mains
the other week. We heard this huge bang, then the lights dimmed for a
moment. Probably someone trying to set up another drugs house,
bypassing the meter box for their hydroponics. I hope they hurt their
fingers. Never thought I'd see that where I live, but there's already
been one removed from our street. The next tennants had a hell of a
cleaning up job to do.

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.

Ours is definitely not grounded at this end. I've had to put the
terminal box back together a few times, after falling tree branches hit
the wire. I discovered the last telescum tech had not properly
terminated the wires, he'd just twisted the drop wire a couple of times
around the ancient heavy duty copy wires leading into the lounge, there
was nothing to hold them together. I didn't do anything that crap when
I first started dabbling with electronics as a teenager.

A long extension cord and a friendly neighbour, perhaps?

I'd have to be a very long one. ;-) I don't get on with my neighbour
after I gave them hell over their dog barking at 3 in the morning.

But there are some rather extreme warnings about not coupling the mains
between buildings. Even other types of common wiring between buildings
has its hazards. My background involves things like theatre and
television station audio and video signal wiring, we go to great lengths
to electrically isolate signals between sites, using transformer,
optical, or RF coupling, to ensure no current can flow between them.
You see some strange groundings of wiring to overcome hum loops, etc.
And I've seen sparks fly from things like the old 50 Ohm LAN coax
cables, as the connector brushed across the chassis.

--
(This box runs FC5, my others run FC4 & FC6, in case that's
important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.

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