coax cable connected to t.v.sparks fly!

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zappy

zappy

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CA.
a customer calls and says that the cable guy was over,he plugged in the t.v to the outlet nearby no problem.plugs in the cable box to a extention cord coming from his basement and thats a different circuit.so cable guy plugs in the coax to the t.v. and it sparks,trips the brkr, and ruined his t.v. homeowner says he know a little electrical and before this happened he was changing some outlets and who knows what else.tells me he plugged in his plug tester and it says hot/neu reversed on the outlets in the basement.the outlet the t.v.was on plug tester says normal.so what i was thinking this is neutral current on the coax?but would that trip the brkr?any advice will be very much appreciated!
 
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zappy said:
a customer calls and says that the cable guy was over,he plugged in the t.v to the outlet nearby no problem.plugs in the cable box to a extention cord coming from his basement and thats a different circuit.so cable guy plugs in the coax to the t.v. and it sparks,trips the brkr, and ruined his t.v. homeowner says he know a little electrical and before this happened he was changing some outlets and who knows what else.tells me he plugged in his plug tester and it says hot/neu reversed on the outlets in the basement.the outlet the t.v.was on plug tester says normal.so what i was thinking this is neutral current on the coax?but would that trip the brkr?any advice will be very much appreciated!
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I'm guessing that the cable box had a 2-prong polarized line cord, so it was being fed hot on what should have been neutral. The neutral likely wasn't connected directly to the chassis, but may have been coupled electrically by some means. Assume something similar on the TV side, though this end would have been connected to neutral (grounded) like it should be.
Now you have the chassis of one device coupled to hot, and the chassis of another device coupled to neutral. What do you think is going to happen if you connect them together? Might not be 120V but 1V is all you need. Had there been enough current to trip the breaker, the person lucky enough to be connecting the cable might have singed the hair on their knuckles...

In a perfect world there would be 100% isolation between the line input and the rest of the device, but hey, what do you expect for a $150 panaphonic TV? Also, wouldn't a cube tap be cheaper than an extension cord? Better yet, if the extension cord is all you have, why not plug it in there and tie it in a big ball and use it like a cube tap?
 
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Just curious, if there was an outlet nearby for the tv then why was it necessay to power the cable box with a extension cord from the basement?:-?
 
thanks for the advice!

thanks for the advice!

yeah i ask him that he said his house was built in the 30's and not alot of outlets.:roll:
 
Every cable box I've ever seen has either a piggyback plug, or a receptacle in the back, sometimes two receptacles.

I suspect a defective cable box was the reason for the initial visit from the cable company. The cable "tech" probably wanted to blame the home's electrical wiring, or the outlet the box was plugged into, and decided to prove his theory by running a cord to plug it into a different outlet.
 
LawnGuyLandSparky said:
decided to prove his theory by running a cord to plug it into a different outlet.
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I am not following you, there is no reason that the TV must be pluged into the cable box.
 
hot to ground

hot to ground

I have run across that before. In my case there was an outlet in a old farmhouse that was in a metal box in the sideways posistion. over time the hot screw vibrated loose and was touching the metal box. there was not a ground back to source so the breaker never tripped but in the box there was a ground wire bonded to the box. this caused a hot to ground making the frame of the cable reciever hot since the reciever was plugged in to that outlet. the coax came from a sat. dish mounted to a metal roof with ground rods. it was possible to read 120 volt between the coax and the frame of the reciever. maybe the outlet in the basement in your case was of the same problem.
 
just came back from the homeowner's house

just came back from the homeowner's house

ok he has old knob&tube no ground he had his outlets wired right but i found a old splice probably from the 1930's on the k&t that was reversed,neutral on hot.i checked his cable box & tv both have polarized plugs.so i tried my ohm meter on the neutral of the cable box and the t.v.plug to see if it might have been connected to the metal housing or the cable jack some how.i got no tone.which makes sense why would you bond the metal housing or the cable jack to the neutral?so the only time the metal housing on the cable box is grounded is when you plug in the coax to it?i checked the coax coming up threw the floor no voltage on it.i'm still not sure why he was getting sparks.i told him to call poco & the cable co.to see if anything on there side is wrong.
 
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iwire said:
I am not following you, there is no reason that the TV must be pluged into the cable box.
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I seem to remember the early cable boxes were that way. You could leave your (non remote controlled) TV in the 'on' position, and the cable box would turn on the TV with the cable box's remote.
 
mdshunk said:
I seem to remember the early cable boxes were that way. You could leave your (non remote controlled) TV in the 'on' position, and the cable box would turn on the TV with the cable box's remote.
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This can actually hurt newer tv's that require power 24/7... so i'm told anyway.:roll: Now most catv remotes will tell the tv and set top box to turn on with the push of 1 button... technology is great isn't it? :)
 
The line to the cable box chassis is isolated, correct? The TV worked fine until the cable box was added.
Get a new cable box and tell us the problem was resolved.
 
iwire said:
I am not following you, there is no reason that the TV must be pluged into the cable box.
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i used to own a cable box that had a receptacle built on it for the tv to plug into. the tv wouldnt turn on when the cable box was off. this was probably 15 years ago at least.

the one i own right now actually is that same way..its pretty old but still works
 
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