A friend doesn’t have cable, but she wanted to see if she could receive anything by hooking the cable from the wall to her TV. When she went to connect the cable the copper wire in the middle touched the threaded ANT. IN (cable) jack on her new Panasonic LCD TV and arced. She said it actually melted the threads.
What would cause this?
Being strong enough to melt the threads, indicates it has contacted the house wiring or the exterior electric lines somewhere. I would say she got very lucky. Something needs to be done to eliminate the hazard.
Assuming she exaggerated, cables do carry a charge and a spark could jump. The cable runs are supposed to be grounded to an external grounding rod, but don’t depend on it having been done. I have used the run of cable in a house as an antenna, but a rabbit ears will pick up as much or more programing from local stations.
Or the outlet the TV is plugged into is wired backwards.
Someone needs to get over there with a DVM as soon as possible.
Explain?
Most TVs use a polarized two-prong plug; you can only plug it into a modern outlet one way. On some TVs, if the outlet is wired correctly, the TV’s ground plane (which includes the threaded part of the F connector) is connected the the neutral line, which is at (or supposed to be at) zero volts. If you reverse this, the TV will still work properly, but the ground plane is now sitting at 120 V. This was more an issue with older TVs; I don’t know how common the practice is today. I do know it’s not the case with my TV.
I just throw it out there as a possibility.
Cable companies escalating their anti-theft-of-service measures?
Some houses have a power-over-cable system to provide power for distribution amplifiers. Hers may be one. I doubt it’s powerline AC, because that would have made a hell of a bang.
Most new TVs have a proper chassis ground and a three-prong power plug. The days of two-prong plugs and “hot-chassis” TVs is long behind us. (Thank goodness!) Barring any serious problem with the electrical wiring at the OP’s friend’s home, the problem is with the CATV cable.
The cable’s shield should be grounded, but funky connections out in the bad weather, mixed with miles-long lengths of cable running parallel to 7200 volt (or more) power distribution wires means the CATV cable can, and will, pick up “stray charge.” Normally, there’s only enough power behind it to give you a bit of a tingle. Another possiblity is “phantom power” placed on the CATV cable to power repeater amplifiers and similar things in the system, and it’s not been blocked from the cable outlet the friend tried using.
Obviously, the OP’s friend needs to call the cable company if they want service, and it will be up the the cable company to make sure their wiring is safe. I’ve never seen stray charge or phantom power be sufficient to actually vaporize metal, (I have seen plenty of small sparks, though) so my suspicions are with some sort of more serious fault.
Hopefully, it will be with the CATV system, rather than the house wiring.
I mentioned it to her. I don’t think she quite understood what I was saying. She said she has a grounded plug. She bought her Philips flat screen because she liked mine. I’ll have to look at my plug. I thought it was two-prong. I wonder if she meant the outlet?
So she got cable and the cable guy got shocked. Apparently he told her the TV was mis-wired. She returned the TV and is awaiting a replacement. In the meantime she’s rented a TV. I don’t know what kind, or if it’s connected to the cable. I’ve emailed her that if the new Philips has the same problem she should look at the outlet.
If I’m understanding the suggestion correctly, she ain’t gonna be able to tell by looking at it. She’ll need at the very least one of those plug-in circuit testers.
Yes, I mentioned that to her last month. What I meant when I said she should ‘look at’ the outlet is that she should ‘have it looked at by someone with a tester’. Knowing her though, I wouldn’t be surprised if – assuming the new Philips does the same thing – she decides it is the outlet and swaps the wires herself. If she gets back to me about it I’ll suggest she report it to her apartment manager so that he can call an electrician.