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.
