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TV transmitting power through coax cable??

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ebisky

Guest
Hi,

A cable technician came out today to do something unrelated to this question. Anyways, while he was working he said he got shocked by one of the cables. He said a device inside my device was transmitting power back through the coax cable. He tested a few of the connections and found that a TV on the main floor of my house was the problem.

Have any of you experienced a problem like this or can tell me what would cause this? He said that sometimes the TV goes bad and can transmit power back through the system. He said worst case scenario is that a splitter goes bad over time or a fire could start. The TV works fine and I have no problems with it.

I have a multimeter but am not sure how to test it out myself. Anyone know?

Thanks for the help.

-E
 

SeanT

Distinguished Member
I've often had shocks off RF outputs on devices, and from aerial splitters - the answer in all cases was either don't be a wuss when handlng the cable, or switch everything off before you touch anything - it's not at all unusual (heh, try working on a phone line when it rings, or a whole rack of phone terminations when a few start ringing!)
 
E

ebisky

Guest
I've often had shocks off RF outputs on devices, and from aerial splitters - the answer in all cases was either don't be a wuss when handlng the cable, or switch everything off before you touch anything - it's not at all unusual (heh, try working on a phone line when it rings, or a whole rack of phone terminations when a few start ringing!)

Hmmmm. Well, supposedly the cable technician went around to all the cable jacks in my house and was testing them with a multimeter device. He said that this certain TV was the one that was transmitting power back through the coax cable and outside to the box.

So what does that mean?
 
D

Deleted member 30535

Guest
Testing involves putting one probe on the centre pin and the other on the casing of the aerial socket.

Sky boxes put out a voltage over RF for the Sky Link units to work (remote handset operation). They can give quite a tingly sensation when touched as well.
 
E

ebisky

Guest
Testing involves putting one probe on the centre pin and the other on the casing of the aerial socket.

Sky boxes put out a voltage over RF for the Sky Link units to work (remote handset operation). They can give quite a tingly sensation when touched as well.

Thanks for the reply.

The casing of the aerial socket would just be the black wrapping around the coax cable or should I be touching the metal area that surrounds the center pin(the piece that turns to screw the cable down)? Also would this be AC or DC current? I think the technician tested the cable coming off the TV.

BTW, this TV is a Sharp 15 inch TV in my kitchen. It doesn't plug into a cable box, the coax cable goes straight into the the TV from outside.
 
D

Deleted member 30535

Guest
Thanks for the reply.

The casing of the aerial socket would just be the black wrapping around the coax cable or should I be touching the metal area that surrounds the center pin(the piece that turns to screw the cable down)? Also would this be AC or DC current? I think the technician tested the cable coming off the TV.

BTW, this TV is a Sharp 15 inch TV in my kitchen. It doesn't plug into a cable box, the coax cable goes straight into the the TV from outside.

Looks like the fault is TV.
 
E

ebisky

Guest
Looks like the fault is TV.

I used my multimeter and put the black connection on the outer metal area and put the red connection onto the center pin. I received a reading of .011 in the 2V range. That's .011 volts right?? That doesn't seem high at all. I checked a few other cable connections. Two of them showed nothing. Another connection I tried showed a reading of .007
 
D

Deleted member 30535

Guest
If it's just a couple of volts I personally would not worry about it. If your TV is working fine then just leave well alone IMHO of course. The sparky may be just looking for some extra work.
 

JohnWH

Active Member
I would imagine it more likely to be the result of a floating earth i.e. it has no earth connection to pull it to '0'. You can measure this by connecting one probe to earth and the other to the outer connection of any of the phono outputs of the device in question, its not uncommon to see around 20V which for me is around the threshold of being able to feel it (my sky box shows ~17V). Note that if any of the equipment is earthed when you hook everything up every thing should be pulled pretty close to 0V by that peice of kit (there will still be a small offset due to the resistance of the cables).

This is typically why you can sometimes see a little sparking when you connect up kit that is turned on.

John.
 

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