Is This a Ground Loop? - AVS Forum
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post #1 of 18 Old 03-01-2007, 07:42 PM - Thread Starter
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I've been fighting this proplem for years! In thinking it was a ground loop with my cable TV, I ran all new RG6, re-grounded the cable to my electric meter, tried all the homemade devices I could find, and today got my VIDEO ISOLATION TRANSFORMER (180-075) from Parts Express. Nothing has worked!

What is the shadow bar moving up my TV?

Please go to YouTube and enter this after the root URL

watch?v=MT7Ho0apEwY

Thanks,
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post #2 of 18 Old 03-01-2007, 08:57 PM
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Can't unsheilded speakers do this?
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post #3 of 18 Old 03-01-2007, 09:17 PM - Thread Starter
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I borrowed a Dish Receiver and dish. No bars! It has to be the cable feed? All TVs in the house have these bars.
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post #4 of 18 Old 03-02-2007, 08:13 AM
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That definitely looks like a ground-related issue. Have you checked your power? Some receivers are more resistant than others. But clearly, the problem is the box and not your TV, since Dish doesn't exhibit the same problem.

Is the power outlet where you have the Comcast STB plugged in....grounded?
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post #5 of 18 Old 03-02-2007, 08:37 AM
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That looks like power supply ripple noise commonly refered to as hum bars. If you look closely there are two bars this indicates 120Hz as full wave rectification creates 120Hz ripple.

First suspect would be the TV's own power supply. But if every TV in the house has this then chances are its coming in on the cable line. I would suspect a faulty PS in a nearby cable amplifier.

Do any of your neighbors have similar interference?

A 'phile and his money are soon parted...
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post #6 of 18 Old 03-02-2007, 08:37 AM
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Quote:
Originally Posted by Damnationdoormat View Post

Can't unsheilded speakers do this?

No.

A 'phile and his money are soon parted...
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post #7 of 18 Old 03-02-2007, 10:04 AM
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What did the cable company techs have to say when they were out?

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
-Bertrand Russell
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post #8 of 18 Old 03-02-2007, 02:33 PM - Thread Starter
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To clear up a couple of items. This is analog cable, no STB, straight from the wall to the TV. I have not called the cable company yet, wanted to make sure it wasn't an inside the house problem.

Today, I bought 100' of RG6, went from the cable company box, through my front door, straight to a TV. Bypassing the box at my house and all splitters. Still had the bars! So, now I can justify calling them. First I'll check with my neighbors, and have everyone call!
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post #9 of 18 Old 03-02-2007, 04:38 PM
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Try a ground isolator device on the cable coax line.
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post #10 of 18 Old 03-02-2007, 06:22 PM
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My vote is for 1101011's explanation. This is a Cable Company problem. Stay on them.
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post #11 of 18 Old 03-02-2007, 07:34 PM - Thread Starter
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Talked to my next door neighbor and showed him the problem. He has digital cable, and this problem doesn't show up.

I really don't want to go digital since I have so many TVs, tuner cards, etc.

11001011 has the best explanation, I'll call the cable company with it. Thanks,
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post #12 of 18 Old 03-02-2007, 08:33 PM
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Buy one of those adapters that allow you to plug a 3 pronged AC cord into a 2 pronged outlet. Then try it on your display device or the cable box. This has worked in a number of our installations. Had this problem with the Motorola cable boxes in this area.
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post #13 of 18 Old 03-02-2007, 08:55 PM
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Quote:
Originally Posted by zoob View Post

Buy one of those adapters that allow you to plug a 3 pronged AC cord into a 2 pronged outlet. Then try it on your display device or the cable box. This has worked in a number of our installations. Had this problem with the Motorola cable boxes in this area.

Don't do it. They are often called cheater plugs. Some call it lifting the ground and is potentially unsafe, because it removes the ground connection for whatever is plugged into it. It solves the hum problem at the expense of safety.

Death by electrical accident is relatively uncommon, but why be the first on your block?

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
-Bertrand Russell
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post #14 of 18 Old 03-02-2007, 09:07 PM
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Quote:
Originally Posted by Mallego View Post

My vote is for 1101011's explanation. This is a Cable Company problem. Stay on them.

Stay on them? He hasn't even called them yet?
Thats a lot of freaking work and money to rule out issues before calling.
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post #15 of 18 Old 03-03-2007, 07:01 PM
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Tool, If you look at his picture on You Tube, you will see the double hum bars. To quote your own web site: A double line rolling up the screen is indicative of a power pack issue at the amp. Forgo all above troubleshooting steps and jump straight to a test set off the tap or a test drop to the customers set. The problem is usually traced back to the closest amplifier housing a failing power pack. Ensure groundblock is up to specs and refer to your maintenance crew for repairs.

He bypassed all the internal wiring and still had the same problem, so I think we can safely assume that the problem is with the cable company.

As far as the comment "stay on them" any reading of the internet postings will reveal the poor customer experiences that subscribers have with the cable companies.

I'm PMing you with some other comments, maybe we can have an off-line dialog.

Mallego.
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post #16 of 18 Old 03-05-2007, 06:06 PM
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To tell someone to "stay on them" when they havent even called is a bit knee jerk. I never said the issue WASNT the cable company. I said that he has lready done enough leg work of his own ( too much ) and should be calling them.

Im aware of all the postings online about poor customer service. I think we are also aware that no one runs to the internet to post what a GREAT and POSITIVE experience they have had.
Dont judge a company or the tech on your doorstep by what someone in a town 1,000 miles away said about their experience.
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post #17 of 18 Old 03-06-2007, 10:14 AM
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I have the same problem as the OP, but I have another one has well. I get diagonal lines on nearly all my channels, some worse than others.

Does anyone have any suggestions on how to fix the hum bars and diagonal lines that I have?

To be honest my analog cable is so bad that have disconnected it from my TV and now only watch OTA. Strange thing is that nobody else in my family seems to care.
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post #18 of 18 Old 03-06-2007, 01:57 PM
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Call for a service call. There are a million things you can check on your own.. but you shouldnt have to.
Just call and have a tech diagnose and repair the issue.

I was at a trouble call for HUM yesterday, double lines, same thing. Sub had contractors out and the electrical meter and mast were replaced and they cut the Telco and cable groundwire.

Hooked it back up- Good as gold.
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