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-   -   Cable issue or wiring issue? (http://www.diychatroom.com/f18/cable-issue-wiring-issue-24976/)

Duchey 08-10-2008 01:21 PM

Cable issue or wiring issue?
 
I've been having an issue with my coaxi cable giving off strong electrical shocks. In fact, it's fried two cable boxes, my TV and three cable techs:eek:.

I had out an electrician and he told me that it's probably the coaxi ground (grounded to the junction box by the meter) and said the the only wires running thru there are a hot and a neutral and that it could get getting back feed. He went on to test the outlets with a plug in meter and they all read "correct", so he claimed that it's not the wiring and that I should have them ground the cable to a water pipe.
SO, the cable company sent out two more techs who I briefed on everything I had been told by the electrician. They said that the ground is not the problem and that "company policy" states that they cannot ground to water, so they replaced all the cable in the apartment and outside. When they tried to hook up the tv they got the predictable shock.

They left telling me that they were sending out a supervisor this week. In the mean time, I started to do a little trouble shooting of my own. Here's what I found.
I took a look at all of the components that I have hooked up to my entertainment center and all of them with the exception of my PS3 are two prong plugs, the PS3 on the other hand is a three prong. I grabbed an old DVD player and hooked it up like normal to the television, the PS3 was also connected to the tv via HDMI. When I touched the coaxi to the back of the dvd player it shocked like hell. I then unplugged the HDMI from the PS3 to the tv and repeated the process,,,no shock at all. SO, I'm thinking that the PS3 must have a short of some type, but just to confirm I decided to pull the only other three prong source in my apartment, my pc. I ran the pc into the tv via S-video and had the hook up the same way to the dvd player. Touched the coaxi to the dvd and boom!,, unhooked the S-video from the pc and nothing.
So, I've concluded that the coaxi only gives off a shock when a grounded plug piece of equipment is hooked up. Does this sound like a wiring issue or could it really be a bad ground on the coaxi?

theatretch85 08-10-2008 01:27 PM

Sounds VERY much to me that its a bad ground on the coaxial line. What you are experiencing is a difference in potential from the equipment ground on your PS3 (or your computer) and the coaxial ground. Ground the coax line to the electrical supply ground and everything should be fine. It surprises me that the cable company couldn't figure that out, they install a ground block on the outside of the house for a reason, its to ground the cable line to the electrical ground! Though its nice that they replaced all the coax cable for you!

chris75 08-10-2008 01:54 PM

1 Attachment(s)
Yep, make sure the coax is bonded to the electrical system.

Attachment 4572

JohnJ0906 08-10-2008 05:14 PM

I agree that the coax should be bonded to the house grounding electrode system, but there is still the issue of where the current coming from.

One cause could be a loose service neutral. The neutral current is trying to find a path back to the transformer. The cable can provide a path, in some cases.

Is your electrical service overhead or underground?
Is your water service (incoming) metal or plastic?
How does the coax run? Is it overhead or underground?

theatretch85 08-10-2008 05:56 PM

I'd be a little curious as to how much difference in potential there is, use a volt meter and check from the shield of the coax cable to a solid ground like on an outlet.

Duchey 08-11-2008 09:46 AM

Well, I'm getting it taken care of tomorrow. The cable company is sending out a Supervisor to "take care of the problem" and the electrician said he could come out anytime, so I'm gonna try to get them both here at the same time and let them duke it out.
The cable company at least put in a damage claim for the TV, but I'm wondering what, if any, action I could take against them for having a hot line ran into my apartment for the past four years? I should at lest get free HBO out of it!:laughing:

theatretch85 08-11-2008 12:23 PM

Quote:

Originally Posted by Duchey (Post 147728)
Well, I'm getting it taken care of tomorrow. The cable company is sending out a Supervisor to "take care of the problem" and the electrician said he could come out anytime, so I'm gonna try to get them both here at the same time and let them duke it out.
The cable company at least put in a damage claim for the TV, but I'm wondering what, if any, action I could take against them for having a hot line ran into my apartment for the past four years? I should at lest get free HBO out of it!:laughing:

Haha, good luck with that, let us know how everything goes.

Duchey 08-18-2008 10:17 AM

Wow, this story just wont end. So I finaly get the cable company to send out a few guy's to fix the grounding problem. I decided as a precaution to unhook any components with a ground plug (three prong) before they try to hook up the box just incase it turns out to be a wiring problem. They run the ground over to the cold water pipe on a water heater, bring in a new cable box and hook it up with no problems. After they left I decided to test out the system to see what would happen if I hooked up the PS3. Sure enough, once the ground plug comes in to play it causes a shock (mind you I used a broken old VCR for this test so no PS3 was hurt:)).
Well, I instantly call up the LL thinking that it MUST be a wiring problem now. The LL is by this time sick of hearing from me, so he pulls out all the stops and gets an electrical engineer to come out. The guy spends two hours testing everything from the breaker to the main box and checking every component for a short. Finally he ends up finding a "dirty" signal from the cable box. He unhooks the coaxi cable, plugs in a three prong plug in to the outlet, puts one end of the multimeter into the ground hole of the ground plug and touches the other end to the outer shiled of the coaxi,,, he gets a reading of 120v on the meter:(. He goes on to test the coaxi at every point till we get to the power line and he cant go any higher. He told me that it's got to be a bad connection from the cable company either at the source or at the ground.
Before he left he gave me his multimeter and showed me how to test the cable like he did. He told me not to let the cable guy's leave till that meter read zero.

J. V. 08-18-2008 11:23 AM

Sending an engineer on a service call? Leaves a meter with you? And says "not to let the techs leave until it reads zero"? They will never read zero unless the engineer left you an analog meter.
I agree with John regarding the loose neutral or another grounding issue in your electrical system. 120 volts is a serious issue and could potentially be lethal, if the circumstance warrants.

Keep us posted. I would like to know what happens. Thanks John

Duchey 08-18-2008 11:36 AM

Quote:

Originally Posted by JohnJ0906 (Post 147569)
I agree that the coax should be bonded to the house grounding electrode system, but there is still the issue of where the current coming from.

One cause could be a loose service neutral. The neutral current is trying to find a path back to the transformer. The cable can provide a path, in some cases.

Is your electrical service overhead or underground?
Is your water service (incoming) metal or plastic?
How does the coax run? Is it overhead or underground?

Electrical is overhead.
Water service is metal, but it's grounded to an outside water heater.
Coax is ran straight from the power pole then into the house(no more than 25feet from the pole to the house). The ground on the other hand is running about thirty feet or so.

"Sending an engineer on a service call? Leaves a meter with you? And says "not to let the techs leave until it reads zero"? They will never read zero unless the engineer left you an analog meter."

Well he was doing it as a favor to my LL, but they joked around about charging the rental company for a service call. And I understand about not getting an absolute zero, but it shouldnt be reading 120v should it? Do you still think this could be a wiring problem or is it pretty much nailed down to the coaxi?

I don't know if it makes a difference or not, but the PS3, computer and anything else with a ground plug all function normaly, no shocks or anything as long as the coaxi is not hooked up. Don't know if that tells you anything or not.

petey_c 08-18-2008 01:43 PM

Duchey, Okay, lemme see if I got this right... Ground to ground (coax to house) and you get 120V, the "EE" says it's the cable Co.. Disconnect the cable where it comes into the house/apartment and remeasure the coax ground to house ground. If there's no 120v, then it's outside the house, if there is, then it's inside.
I had a similar problem in a neighbor's house. Turned out to be a missing/energized ground on the circuit the TV/cable box was plugged into. He had 120v on the ground (which obviously wasn't connected right). The circuit started out at a convenience outlet next to the panel (right near the water ground) and ran all over the house (basement, bedrooms, attic, etc...). I pointed out that on the outlet ground to water ground was 120v. He said, "Oh yeah. I remember one time I touched the outside of the metal box and the shutoff valve and I got a helluva shock."
Do you have 120V ground (coax) to ground on any other circuits? (an extension cord will help here). Turn off the breaker on the circuit that the TV/cable box is on (I'm assuming for argumentí s sake that this is where the problem lies. This will eliminate false positives in case you plug into another outlet on the same circuit) and measure your voltage (should be zero) on the ground of the extension cord to the coax ground. If it's zero, I'd start (or have the LL's electrician) to trace the circuit back to its origin (or work from the panel outwards) and check the ground/neutral at every point along the way. Best of luck and let us know what the fix is. pete

Duchey 08-18-2008 02:02 PM

Well, he (the EE) measured the coaxi all the way up to the wall outlet inside of the house and got the 120v reading the whole way and said that it was coming from outside. So what your saying is that I need to test the cable outside the house with a house ground and if I get 120v then it's coming from the cable? We also measured it in two different rooms from three separate outlets that I belive are on two different circuits (will test when I get home).
I'll try to do what you posted when I get home, but my question is why do I only get a shock when the coaxi comes into the picture? Why dont I get shocked when hooking up the computer or PS3 normaly if it's a ground problem? Things only get nasty once the coaxi enters the picture.

AH,, I do have another cable connection in the bedroom and I'm almost certin that the outlets are on a separate circuit. So, if I test the house ground to coaxi ground in the bedroom and it comes up 120V then I've got a problem with the coaxi?

jrclen 08-18-2008 04:39 PM

The ground is not the problem. The problem is whatever is putting 120 volts on the cable shield. Your biggest problem at this point is an electrician who checks outlets with a plug in tester rather than trouble shooting the actual problem with a volt meter. I think you need a real electrician before someone gets hurt or graveyard dead.

petey_c 08-18-2008 05:18 PM

Well, he (the EE) measured the coaxi all the way up to the wall outlet inside of the house and got the 120v reading the whole way and said that it was coming from outside. So what your saying is that I need to test the cable outside the house with a house ground and if I get 120v then it's coming from the cable? You can check it at the same place you tested it before. You just have to disconnect the coax input from where it enters the house. Usually they have a barrel type connector with two water proof "boots." Slide one of the boots out of the way and disconnect the coax from the connector, then make your measurement.

We also measured it in two different rooms from three separate outlets that I belive are on two different circuits (will test when I get home).
I'll try to do what you posted when I get home, but my question is why do I only get a shock when the coaxi comes into the picture? Why dont I get shocked when hooking up the computer or PS3 normaly if it's a ground problem? Things only get nasty once the coaxi enters the picture.


What type of plugs do the PS3 and computer use? If they aren't grounded plugs (3 prong) 120V on the ground would have no effect on them.

AH,, I do have another cable connection in the bedroom and I'm almost certin that the outlets are on a separate circuit. So, if I test the house ground to coaxi ground in the bedroom and it comes up 120V then I've got a problem with the coaxi?
If it is on a separate circuit you may be correct. Disconnecting the coax outside should narrow down the possibilities.

220/221 08-18-2008 05:34 PM

When you lose a neutral, the current is very resourceful finding ways to get back. Find out exactly where the power is coming from by process of elimination (turning off branch circuits one at a time)


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