120VAC on my RG6 inner conducter

[ZapT]

Got a service call today for an electrician. The customers has been getting a shock from her cable for years. The cable man hooked up the tv and blew up the HDMI and cable box. TV had a service contract so it was replaced. They ran a new RG6. He put a tool on his RG6 end it showed 120VAC. Parts of this house were renovated by a previous owner(non electrician). I cant stand when this happens, anyway. 120V appears only when this breaker for this room is on. Also the metal nail on box is also live. I cant believe it. The box is grounded. There has to be a hidden splice box with no grounding cond from the panel. I ran a dedicated plug for the tv. I figured I would post this before I abandoned that circuit and refed the room to take care of the problem. The splitters are bonded. Any thoughts.

 

[ActionDave]

Old two wire circuit somewhere in the house with the hot and neutral reversed, or something similar I bet.

 

[Hv&Lv]

I can see how the box nail could be hot, and grounded by the way you explained your guess.(hidden box)
I have a hard time understanding how the core wire of the RG6 cable is hot? I am going to assume the wire has never been connected to the cable companies feed in. (if at all possible)
I wonder if the RG6 is ran with the power, and the unterminated end is still hidden in a box somewhere touching the hot wire? If the end is cut flush and touching the gold screw, this could also explain how the grounds are heated up

 

[Speedskater]

I would think that the tool was a non-contact voltage probe. Don't think that most cable tech's carry a special tool to measure 60Hz line voltage across the connector pins. But if 120V is measured from the co-ax to something else, then that 120V will be on both the center pin and the shield. A 120V difference between the center pin and the shield will blowup the cable pre-amp.

 

[kwired]

Are you sure there is not a problem with electric service (likely the neutral) and the Coax is simply a ground reference?

 

[Strathead]

Here is my suggestion for troubleshooting it, or at least a start. Use a circuit tracer, depending on the features and accessories the hook up may be different, but hook one side to the RG6 hot conductor, and the hook the other end to a wire extended to a known good ground, (receptacle on different circuit, the panel, a water pipe) use the tracer to follow the RG6 in the wall. At some point you should find the place where it crosses paths with the 120V circuit and heads back toward the panel.

Oh, check voltage after you hook up the tracer transmitter to make sure the 120Volts has enough power behind it to operate the tracer.

 

[CarlAshcraft]

Based on the information that you provided, I doubt my situation is the same as yours, but here is what I ran into...

I was called out to a service call several years ago. The "cable guy" was terminating the ends of the coax cable and was shocked. This customer was
living in a new home that had a structured wiring low voltage panel. The electrical company that had trimmed out the house did not terminate the
electrical wire that was inside this structured wiring panel and the hot wire from the romex that was running into the panel was touching the panel
making any low voltage wires grounded in the panel hot.

 

[Hv&Lv]

Are you sure there is not a problem with electric service (likely the neutral) and the Coax is simply a ground reference?

We had one of those one time. A neutral connection at the pole was bad, but the connection to the Xf and pole ground was good. The cablevision was grounded to the pole ground, and again at the ground wire at the house. Effectively the coax ground was the neutral going back to the XF. After complaining that the reception was bad, the cable guy began lifting his ground from the house and showing the homeowner all the sparks that were coming off of the ground as he slid it up and down her ground wire.
He failed to realize her microwave and the computer, along with a couple of other minor items, couldn't take this voltage surge he was creating.