Interference on flat screen tv

[bobbyho]

Got a call from someone who has interference on his flat screen when it is plugged into a grounded outlet. It has a 3 prong male cord. When he plugs into a 2 prong adapter and plugs into the same outlet, problem goes away.
He has Diva dimmers (I think) with low voltage recess lights. When 3 prong is plugged into grounded outlet and dimmer is used, problem is amplified. He had run an extension cord to another room and problem was still there. When the coax is disconnected, problem goes away. Does this sound like a strand of the coax hitting it's conductor? Sorry for the long winded question, I have not been to the house but just in conversation with the homeowner. Any ideas would be appreciated.

 

[mdshunk]

I guess that's what they call a ground loop, if I'm not mistaken. Maybe search for "flat screen" and see what you come up with. I know it's been discussed before.

 

[Chamuit]

Make sure and check to see if the ground supplying the network interface of the TV company's equipment is there. Had a job two years ago where a CATV guy helped me and one thing he mentioned was checking the ground.

 

[MAK]

If you can not find the source of the problem you could try a ground loop isolator. I believe there are some made for CCTV applications. My terminology might be off a little bit.

 

[bobbyho]

I had him try plugging the coax into the wall jack but just the conductor, no metal to metal contact. Said the signal seemed good but goes crappy as soon as metal to metal contact. I think this may be it. Does it sound like stand hitting the conductor? (Did I ask that already, I want to go to sleep:roll:

 

[quogueelectric]

This is what you are looking for I use the Holland ccl-1 ground isolator also commonly called a ground breaker. They are a godsend.
I get mine from a local catv stereo supply warehouse and this model is about 10 bucks and works great I found one on ebay for you if you dont have time to look around for the holland model.
Your underlying problem is that you have voltage induced on your cable shield and when you make your final connection the set ground is tied to the service ground and the cable shield will drain to the ground that has a problem somewhere down the road.
Most customers will think you are trying to screw them when you tell them they have a cable problem from homeowners doing thier own cable distribution.
This is an easy fix but not the right job that will get you your money so you can hit the road> This is why I stock a few of them on the truck. I will gladly install a clean line for you for 99 bucks a line all day long. Ground breaker will cost you 40 its your picture quality what do you want to do? http://cgi.ebay.com/TII-CABLE-TV-CO...VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

 

[bobbyho]

I want to make sure I am understanding you. Are you giving them the choice of a new line or installation of the ground breaker? I thought the ground breaker was simply a test piece but it sounds as if it something that is installed permanently.

 

[mdshunk]

You might want to start by confirming that the CATV splitter/entrance bridge is grounded to the same place as the electrical service. Make sure that both grounds are at the same potential. The older CATV entrances could be grounded to almost anything metal, including their own wimpy driven rod, or no ground at all.

 

[quogueelectric]

I want to make sure I am understanding you. Are you giving them the choice of a new line or installation of the ground breaker? I thought the ground breaker was simply a test piece but it sounds as if it something that is installed permanently.

It is kind of like putting in a twin breaker or selling a new service. Sometimes if you live in a highrise or a condo you cant control the cable quality with hack maintenance do it yourself homeowners splitting the cable to the moon without the shield carrying continuous you will pick up noise . when you tell the customer I have just installed your beautiful plasma tv for between 500 and 1000 dollars and now I am telling you you have a lousy picture because of a preexisting cable problem that didnt show up until you went hi def. I am showing you you have a voltage on your cable shield and it is not my problem so you give them a choice either rewire the houses cable system with rg6 quadshield at 100 bucks a drop or for 50 bucks I will install a ground breaker and call it a day. They have never gone for the rewire in my experience. Just put a bandaid on it Hey they work great!