AC Voltage on Coaxial Cable (Cable TV)

Question

I have an issue with my cable box (with DVR). Every morning it displays the word "Boot". I have to reboot it in order to restore cable service. I called the cable company (Comcast) and they came out and replace the DVR box as well as it's companion box. Comcast stated they reboot X1 boxes every night and mine is getting hung during the reboot.

The new boxes didn't help. I called again and they sent out another tech. This tech did some testing and stated there is AV voltage on all four of my cable line.

I have much more detail but when I included it and tried to send this question, I got a response stating this question looks like spam.

Has anyone experienced this issue with AC voltage on cable lines?

Here is more detail . . . . . The cable comes in to my house (which is grounded with a grounding hub) and goes into an signal amplifier. I have four home run cable lines going to 4 different TV's from the amplifier. If I disconnect any one of these home run lines and using a volt meter measure from either the center conductor or the connector itself, I get anywhere from 42 VAC to 54 VAC (depending on which line I measure). With the cable still disconnected from the amp, I then measured at the cable box. I disconnected the cable from the wall (cable still connected to the cable box) I get the same AC voltage. (Measuring from the cable to the ground prong on a standard 120v wall outlet). The cable box also as an HDMI cable going from the cable box to the TV. I disconnect the HDMI cable from the TV and measured the outer shield on the HDMI cable to ground and again, AC voltage (????).

I then measured from the back on one of my TV's from the male coax connector to ground and AGAIN AV voltage? No other cables were connected to the TV other than the 120V power line. I attempted to isolate which circuit might be causing this very strange issue. By the way, all four TV's are on different circuits coming out of my breaker panel. If I turned off the circuit that I was measuring, obviously the AV voltage would go away. However I was unable to isolate any single circuit. I ended up calling an electrician.

He came out and was puzzled from the start. He disconnect every ground wire AND neutral wire from the panel one by one but we could not isolate a bad circuit. He checked all grounds and outlets the TV's and cable boxes are plugged in to and all were good. I forgot to mention above that if we connect the cable back to the cable amp (which is grounded), I get no AV voltage back at the cable boxes. To try and narrow this down, I got my generator out and connected one TV with it's cable box to it. The TV and cable box was totally disconnected from anything in my house. It was only connected with an extension cord to my outside generator and I was able to measure AV voltage on the coax coming out of the cable box. The electrician gave up. But now I am out $200 and I still have the issue every morning having to reboot my cable box.

Answer 1

If your cables are running parallel to a power cable they will induce a small voltage on the line. The cable should have a ground wire at the entrance of the house this is usually bonded to a metal water pipe. Verify that the cable ground is going to a well grounded place (metal Pipe or Conduit that is grounded). If you do not see a ground wire from the external cable box at the entrance to the house it was not installed properly, a ground needs to be added and that should eliminate your problem.

Answer 2

You might have a defective TV that is leaking current.

One of these might help: Voltage Blocking Couplers

Answer 3

If your home is grounded properly the house ground will bear the Load of most of the voltage. Your RG-6 cable(COAX) will show 0.4 VAC. IF any voltage is on the center conductor then you will interfere with return path frequencies. This is crucial because these determine your out bound speeds and can break channel bonding. Channel bonding is the technology that allows for speeds to be faster on the downstream traffic. Being as voltage is low pass(2 - 60Mhz) it will cause interference in the return path frequencies (DOCSIS 3.0 Specification) 5-45Mhz . It will appear as a small hump on a spectrum analyzer. Now if you home is converted/updated from whats known as a pre 65' build, then you will in fact induce voltage due to daisy chained grounding. Why does this happen? well a ground wire is 7 to 11 gauge copper according to ANSI standards. Your COAX center conductor is highly conductive copper coated steel. The center conductor is made to be extremely conductive so that frequencies which travel via electron flow can indeed ... flow... So its all relative. Make sure you house grounded, you should NEVER have voltage on your COAX. If it exceeds 50 VAC then it will cause issues. Also keep in mind that if the circuit that's over loaded is not bearing a full load then the reading you see on the Volt Ohm Meter isn't showing you the whole picture. I have seen this for years now where customers will turn on their washing machine while I am testing this and that reading jumps from 50 to 100 VAC.This is because they are on the same circuit at the panel.

I hope this helps to clarify the issue.

mike-

Answer 4

I think I may have just solved a similar problem. The customer kept blowing out her cable box. She called the local power company because the cable installer said the ground block was melted internally and that he kept getting shocked. PECO came out and as a favor tested her electrical system. One by one he would turn on each breaker. When he turned the heater (warm air) he noticed the the voltage across the coax spiked to 7 volts AC. He then said it's either in the line or a voltage leak from the blower motor. He left and said call your electrician. So when I got there I inspected the BX cable not MC and noticed that there were no anti shorts being used at each termination (4 total). I replaced all connecters with proper connectors with anti shorts and the problem seem to disappear, I was reading (0.1) volts instead of 7 volts AC.

Answer 5

Your neighbor probably lost a neutral in electrical service!Your cable became their neutral to your ground!I've seen where service entry cables outside neutral/ground wrap rot apart!Could be neighbors problem!

Answer 6

I have Cox Cable hear in Oklahoma same problem. They sent out a tech that found voltage coming from the main line in my back yard. He changed out the metal head that all the cables run into. Cable is working better but they still have a problem with that new line that was installed 3 years ago.