high voltage readings on catv wiring

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arusso

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i am wondering if anyone has run into a problem with high votage readings on catv wires. i currently have a problem when i connect the catv wire to a television set i get a reading of 170 volts from the cable wire to either hot leg and if i disconnect the wire from the television i read 120 volts. i have never run into this problem and don't think it's normal. the cable company has told the customer that he has foreign voltages in the house and that is why it keeps burning up the catv connection outside.i was wondering if anyone has a solution too or a direction to start looking for this problem.
 
I have come across that before. I would guess it has to do with 1 or more of the converter boxes attached to the premise wiring. Possibly an amp that went bad. I am amased that the CATVCO hooked his service back up knowing of the issue.

~Matt
 
divide and conquer

1st disconnect the house from outside cable, check ea side

disconnect all equipment and check for power on cables. if its a skinned cable then sheath will probably have voltage

connect equipment discretely. if there is faulty equip you will get voltage on cable conductor when you connect the faulty equipment

use a wiggy though and make sure you are getting real voltages
 
nakulak said:
divide and conquer

1st disconnect the house from outside cable, check ea side

disconnect all equipment and check for power on cables. if its a skinned cable then sheath will probably have voltage

connect equipment discretely. if there is faulty equip you will get voltage on cable conductor when you connect the faulty equipment

use a wiggy though and make sure you are getting real voltages
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I agree with all this, and would like to add: check the CATV ground connection.

~Matt
 
Start at the demarcation point, disconnect it and look back at the CATV line. If it is clear, the problem is from the residence. If so then divide and concur by disconnecting all terminations and reconnect one at a time.

My gut tells me you should closely check the demarcation ground block and make sure it is properly bonded to the AC service ground.
 
dereckbc said:
Start at the demarcation point, disconnect it and look back at the CATV line. If it is clear, the problem is from the residence. If so then divide and concur by disconnecting all terminations and reconnect one at a time.

My gut tells me you should closely check the demarcation ground block and make sure it is properly bonded to the AC service ground.
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Possible a faulty ground?
 
when i connect the catv wire to a television set i get a reading of 170 volts from the cable wire to either hot leg and if i disconnect the wire from the television i read 120 volts.

To either hot leg to the cable connector outside you should have 120 volts. The outside of the cable is ground provided by both the ground block and the connection out on the street.

But measuring between the coax fitting and the hot legs is not the way to go. What is the reading:

A) From the disconnected cable fitting to GROUND.
B) From the TV connector (without the cable connected to it) to GROUND.

Another question I'll ask is if this is the only TV. I would also check the ground block (it is NOT a demarc, none of the cable wiring is the owner's responsibility) to see that the ground goes back directly to the service ground. What side of the ground block is the fitting burning up? If it's the house side the ground block ground is good and there is a stray voltage being put on the cable, most likely by a defective TV.

-Hal
 
arusso said:
i am wondering if anyone has run into a problem with high votage readings on catv wires. i currently have a problem when i connect the catv wire to a television set i get a reading of 170 volts from the cable wire to either hot leg and if i disconnect the wire from the television i read 120 volts. i have never run into this problem and don't think it's normal. the cable company has told the customer that he has foreign voltages in the house and that is why it keeps burning up the catv connection outside.i was wondering if anyone has a solution too or a direction to start looking for this problem.
Click to expand...

Somthing doesn't make sense here.
170 volts to a hot leg what points are you mesuring to, what are you using as a meter, cable uses a 60 volt DC power supply which if not DC blocked at the pole can give you weard voltages at the house, but that seems very un likely.

If the cable connection is failing, it is because of current on the cable. this would mean a weak or lost neutral connection at or before the service, the cable sheild is bonded to the MGN at the pole and to the grounding at the house, this puts in parallel with the neutral conductor and if you loose the neutral, it will then carry all of the neutral current back to the transformer, if no other paths are availble, if this is an old `120 volt service, it will carry all the current of the house.

if this is the case I would be asking the customer if they have noticed lights getting briter or dimmer, if so look for a bad neutral problem, most likly it will be ahead of the service maybe at the pole, which the utility would have to be called to checked.
 
arusso said:
i am wondering if anyone has run into a problem with high votage readings on catv wires. i currently have a problem when i connect the catv wire to a television set i get a reading of 170 volts from the cable wire to either hot leg and if i disconnect the wire from the television i read 120 volts. i have never run into this problem and don't think it's normal. the cable company has told the customer that he has foreign voltages in the house and that is why it keeps burning up the catv connection outside.i was wondering if anyone has a solution too or a direction to start looking for this problem.
Click to expand...
As others mentioned - see if the power in the building is doing the same - i.e. lost neutral anywhere....

As for the CATV - the shield of the CATV feed is grounded - or should be - measuring voltage to either hot leg should be ~120v.... ;)

However with this TV connected - you are getting this extra voltage - see if it is being generated by the TV itself.... Measure voltage between the shield of the input for the TV equipment to the ground of the outlet with a DMM - not a wiggy! Then do the same at the demark with everything inside disconnected from it.

Additionally I would also check all of the coaxial connections for shorts while disconnected from both the source CATV and any equipment with a 75ohm coaxial tester - just to give the inside wiring a pass. Maybe even by-pass all of the inside wiring with a long RG-6Q jumper from the CATV demark to the TV - just to make sure you looking for the problem in the right places.
 
hbiss said:
...
Another question I'll ask is if this is the only TV. I would also check the ground block (it is NOT a demarc, none of the cable wiring is the owner's responsibility) to see that the ground goes back directly to the service ground. What side of the ground block is the fitting burning up? If it's the house side the ground block ground is good and there is a stray voltage being put on the cable, most likely by a defective TV.

-Hal
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Hal,
If you are trying to say that the homeower has no responsibility to the internal cable wiring, why does our cable company have a $4.95/month "home wire maintenance" optional charge? It is to cover any required repairs to the cable in the house. If you don't have it the charge a service fee if they have to come out and fix anything.
 
If you are trying to say that the homeower has no responsibility to the internal cable wiring, why does our cable company have a $4.95/month "home wire maintenance" optional charge? It is to cover any required repairs to the cable in the house. If you don't have it they charge a service fee if they have to come out and fix anything.

Let me see if I can explain it for you. The homeowner owns the wiring and they are responsible for having the cable company maintain it. That's what the charges are for. Some cable companies don't charge, others do.

-Hal
 
hbiss said:
If you are trying to say that the homeowner has no responsibility to the internal cable wiring, why does our cable company have a $4.95/month "home wire maintenance" optional charge? It is to cover any required repairs to the cable in the house. If you don't have it they charge a service fee if they have to come out and fix anything.

Let me see if I can explain it for you. The homeowner owns the wiring and they are responsible for having the cable company maintain it. That's what the charges are for. Some cable companies don't charge, others do.

-Hal
Click to expand...

I guess another way to explain this, is you are responsible for signal leakage if you maintain the cable, FCC can impose up to $10k in fines on the cable company and up to $2k on you if you allow leakage to continue after being notified about it, so most cable company's will go around and do signal sniffing checks periodically to beat the FCC from doing it, cable uses all the frequency's across the radio band, and this includes police, Fire, Aircraft.
but they don't have the right to come into our house but they can just disconnect us.

Had a neighbor split in an outdoor antenna to his cable to try to pick up a channel that wasn't included in our channel line up, he knocked out the communication from Chicago airports to planes landing in Chicago. I saw the citation he got and was told of the big one the cable company got.

Hope this helps keep someone from doing a hack job at hooking up cable.
 
Hmmm... Is that why I can't use my cell on the plane??? With so many 'legal' hacked up CATV installs - it is a wonder why so many planes are not falling from the sky.

I'm sure you neighbor got busted, and there are some radio freq's on there - but the reset is just pure cable company propoganda to help control a technology that has gotten out of their control - JMSO
 
The other side of the coin regarding signal leakage and it's ramnifications is ingress. If you have signal getting out you will have signal getting in. Ingress will cause problems that can range from your own equipment to knocking out the entire node that feeds all the subscribers around you.

This is not just cable company propaganda, it happens all the time. I used to laugh at the cable company's advertising 20 years ago to combat theft of service. They always made it a point to say the the hackers will disrupt service to other subscribers, so if you see them turn them in. Well, the part about disrupting service to others wasn't exactly always true back then. But now it is.

-Hal
 
I can't believe I got a service call today, for the exact same thing in the OP of this thread, the cable company had told the customer that he has foreign voltages.
Must be a cable thing:roll:

current was unreadable, but when you disconnected the cable at the TV (Panisonic 32" CRT) you can read about 170 volts with a DVM between the cable and TV jack, after doing some current sampling and voltage checking, I checked the outlet the TV was plugged into and it was reversed polarity (hot & neutral was switched)
I fixed the receptacle and the voltage was gone.:D

The reason the cable company was called, was the digital cable was pixeling very badly on all the TV's in the house, they ran a voltage trace and found voltage coming from the TV in the basement.

I have the exact TV out in my garage so I did a little investigating and found that the X-ray protection L-C circuit is in fact tied from the chassis to the polarized prong (neutral) of the two wire plug, the shield is also tied to the chassis, so when the receptacle is reversed it will drain through this L-C circuit to the chassis causing a RF ground loop between the hot and cable shield causing the interference.

So now I know to check the receptacle first the next time.:cool:
 
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