Home>Discussions>ELECTRICAL & LIGHTING>Voltage in coax from tv, tivo & cable box...
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Voltage in coax from tv, tivo & cable box...

So here's the situation. We have bad cable reception on a tv in our house, and we have 3 other tvs that are fine. The main cable line comes into the house with no electricity on it. It splits in our utility room to all the other tvs in the house. Now don't necessarily get this next fact fixed in your mind - but the tv with the electrical problem is in the OLD secton of our remodeled house, and the GOOD tvs are in the new section. So, we have old knob-and-tube ungrounded recepticles in the old section, where the problem tv is. So, of course, our first guess was that our tv, cable box, and tivo were all just grounding via the coax because the poor little things had no ground in the super-old recepticles. HOWEVER - we did a little test and ran an extension cord from the new kitchen (with romex grounded GFI's) to the missbehaving entertainment boxes and STILL had: 3 volts from the TV, 20 volts from the large cable box, and 20 volts from the TiVo. Also, none of the plugs from the entertainment equipment have a third ground prong. We tested each one seperately, (completely disconnected from all the other equipment) and still had these readings. I asked 2 electrician friends and they had no ideas. The problem is I have no idea what to do! It's not noise, it's electricity, and it shocked our cable guy when he touched the coax and hot water heater.
How can these things backfeed 20volts each!??

Re: Voltage in coax from tv, tivo & cable box...

that all sounds confusing, but first ya wanna try to figure out exactly what is causing the problem.. so take your cable box that might be the problem and try it at another tv that was working correctly, if it works fine then, its not your cable box.. just keep going right down the line.. next try the tivo. then try a differnt tv. process of elimination.. if none of them seem to be the problem, see if you have a signal booster anywhere, might possibly be that.. also check in your basement.. im not sure about cable, but i know my sattelite is groudned to the water line, which in turn to the electrical panel.

Re: Voltage in coax from tv, tivo & cable box...

ground loop ?

neutral to ground short or leakage ?

hot and neutral reversed ?

Re: Voltage in coax from tv, tivo & cable box...

I believe other posters have stated to call your cable guy to replace your cable boxes, as they are the culprit.

Re: Voltage in coax from tv, tivo & cable box...

So this voltage problem is happening in TWO entertainment center areas at the end of our house that is on the OLD knob & tube wiring. The kitchen and computer room tvs are fine in the NEW section of the house with new wiring.
So I did the test:
Took the 10 volt producing vcr from the OLD section of house to kitchen, attached it to coax, and now coax is reading 10 volts.
WHY is this happening????
EVERY tv, vcr, cable box, and Tivo in the OLD section of our house creates it's own electrical backfeed into the coax.
EVERY tv, vcr and cable box in the NEW section of the house DOESN'T.
AND if we take an "infected" device from the OLD house to an uninfected coax line in the NEW house, the uninfected line is now infected with backfed electricity.
SO, my question is why? Why are all the devices on one side of a house back feeding and all the devices on the other side not?

I mean, I'm ready to call for an appliance exorcism!

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