HDMI cable backfeeding Voltage from TV to cable Box - AVS Forum
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post #1 of 39 Old 07-03-2011, 02:09 PM - Thread Starter
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For the past month I have been going back and forth between Cable repairman and the Geeksquad. I have a new Samsung HDTV that burned out a cable box. The Cable Co, says that the TV was backfeeding 40-60 volts into the cablebox via the HDMI cable. Since they have seen this with new TV's they said get the Geeks to fix it. At first the Geeks said it wasn't the TV, then decided to replace
the 2 major boards inside (warrantied, but over $800). The electrician checked the outlets and said all was fine. But, the TV is still backfeeding the voltage into the cablebox, and the cable co. says people who keep frying boxes won't get new ones. They say these Samsung TV's are not properly grounded inside. I'm just the consumer stuck in the middle, what do I do?
I bought a home theatre surge protector with cable outlets for $100, no difference.. What could it be?
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post #2 of 39 Old 07-03-2011, 02:18 PM
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#1) Disable the Anynet feature on the TV.
#2) Try using component cables from cable box to TV.
#3) Replace the TV. Although it may be drastic, if this were a major issue, I'd assume there would be more complaints.
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post #3 of 39 Old 07-03-2011, 03:56 PM
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Have you checked to see if the cable is properly grounded where it enters the house?
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post #4 of 39 Old 07-03-2011, 04:40 PM
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I had a similar problem. Purchase an IDEAL Analog Multimeter GFCI Receptacle Tester.

http://www.lowes.com/pd_292761-12704...7C1&facetInfo=

Check your outlets with this device, it is likely that one of them has polarity reversed. I fried a computer, satelite receiver, satelite LNB, and hdmi switcher because of this exact problem.

It is fairly easy to reverse the wires once you find the problem, just be sure to turn off the breaker or remove any fuses before working on the outlet.

Hope this helps.

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post #5 of 39 Old 07-03-2011, 04:50 PM
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Forgot to ask a few questions.

Are all your components sharing the same surge protector, or was the TV installed with a new electrical outlet running behind the flat pannel? Some do this to hide the cabling and sometimes the polarity gets reversed.

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post #6 of 39 Old 07-03-2011, 09:49 PM
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Welcome to the forum.

The newer pieces of equipment use switchmode power supplies that produce more leakage current than the older equipment that used conventional transformer power supplies.

There is always some leakage current on the case of equipment, even when it is operating properly, and when you have many pieces of equipment connected together the leakage currents add together. With pieces of equipment that have a 3-wire cord, that leakage current is shunted to ground by the grounding pin. With pieces of equipment that only have a 2-wire polarized plug, the potential leakage current exists on the case and coax ground connection.

If a piece of equipment has a 2-wire cord, and the case and shields of the connectors are not grounded, the leakage current will seek a path to ground through other equipment, or you, if you are grounded. I experienced a mild shock when I had many pieces of equipment connected together that were not grounded and were connected to a temporary outdoor antenna. For safety, I hunted for the source of the current until I understood what was happening. I have detailed my experience here:

Voltage/shock issue
www.avsforum.com/avs-vb/showthread.php?t=1255983

my post #4
www.avsforum.com/avs-vb/showthread.php?p=18772087#post18772087

For other threads with your kind of problem enter Voltage/shock issue in the search box at the top of this page.

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post #7 of 39 Old 07-04-2011, 07:48 AM
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I would try the receptacle tester first, it's only $8 and this is a common problem with hdmi. Just google the phrase "sparks from hdmi" there are many conversations about this. The one that helped me involved the destruction of a ps3, xbox 360, new television, and cable box.

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post #8 of 39 Old 07-04-2011, 11:32 AM
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After reading about the damage caused by HDMI (High-Definition Multimedia Interface), I'm starting to think of it as Highly Destructive Multimedia Interface

CNET Quick Guide: HDMI and HDMI cables
reviews.cnet.com/hdmi-guide/
Quote:


If HDMI compatibility problems are plaguing your home theater, you can try swapping different products in until you get a better match, but that is expensive and time-consuming. Cable boxes are notoriously troublesome HDMI products, and unfortunately you're usually stuck with whatever box your cable company offers. If you can't fix your problem, there's no shame in going back to component video. Manufacturers and salespeople often tout the visual benefits of HDMI over component video, but the reality is that the difference between HDMI and component video is pretty small--again, we're betting the majority of viewers would never notice. The real trade-off is on the audio side, since you'll need to connect additional digital audio cables (optical or coaxial), or deal with bulky analog audio cables.

freemsuz:
Please let us know how it works out.

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post #9 of 39 Old 07-04-2011, 11:55 AM
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Quote:


If you can't fix your problem, there's no shame in going back to component video. Manufacturers and salespeople often tout the visual benefits of HDMI over component video, but the reality is that the difference between HDMI and component video is pretty small--again, we're betting the majority of viewers would never notice.

Which is a reason I suggested this in post #2. Also... if problem reoccurs when using component, then you have eliminated HDMI as the "problem" and you can look elsewhere to try to isolate the problem.
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post #10 of 39 Old 07-04-2011, 12:43 PM
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Are you sure the problem is with the TV and not the cable box? The reason I'm asking is most consumer AV gear is two wire AC power so it is possible the chassis is as some level above ground.

As others have posted use an outlet tester to verify outlet is wired correctly.

Disconnect the TV from the Set-top-box, but except for that keep everything connected normally.

With a multi meter measure the voltage between Green Safety ground and the chassis of the TV. Use the Antenna Coax shell for a convenient ground. Measure from ground to the HDMI connector shell. Should be little or no voltage. Try reversing the power plug to see if that affects reading.

Do the same for the set-top-box. Again should be little or no voltage between the exposed metal parts and Safety Ground. If there is disconnect the coax cable from the set-top-box. Is there still voltage on the set-top box?

If there is voltage on the outer shell of the coax cable probably means the Cableco did not properly ground the cable where it enters your house.
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post #11 of 39 Old 07-04-2011, 02:08 PM
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And... for the third time. Remove the HDMI cable, replace with component and observe. It problem persists, have the cableco diagnose and resolve because you've eliminated HDMI as a suspect. If problem goes away... then back to square one to determine if it's the TV or the cable box.
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post #12 of 39 Old 07-04-2011, 09:09 PM - Thread Starter
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Thank you all for the suggestions. I have copied all of them to present to an electrician. The Cable guys (one is an electrician) and the Geeksquad guys who also claim to know everything, after some squabbling, agreed it was the TV. (Cablebox replaced), innards of new TV replaced. They checked the cable ground, and checked all components against each other, but it's still happening as the cable box's hard drive is spinning when its not on.
I don't understand any of it!!!! I'm hoping an impartial electrician will figure it out.
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post #13 of 39 Old 07-04-2011, 10:40 PM
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Quote:
Originally Posted by freemsuz View Post

Thank you all for the suggestions. I have copied all of them to present to an electrician. The Cable guys (one is an electrician) and the Geeksquad guys who also claim to know everything, after some squabbling, agreed it was the TV. (Cablebox replaced), innards of new TV replaced. They checked the cable ground, and checked all components against each other, but it's still happening as the cable box's hard drive is spinning when its not on.
I don't understand any of it!!!! I'm hoping an impartial electrician will figure it out.

Why do you want to call an electrician to check something so simple? How much are you getting charged each time these guys come out? Just try the simple things first.

Would be cool if you answered a few of the questions asked of you, would make it easier for us to help solve the problem.

I am pretty sure it is a polarity issue.

By the way, the hard drive on the cable box spins when it is off because it will actually record movies when it is not being watched.

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post #14 of 39 Old 07-05-2011, 08:34 AM - Thread Starter
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I am trying to answer the questions, but I don't know much about this stuff myself, so have to rely on what the TV, Cable, and eletricians are telling me. The "Geeks" last suggestion was that something is not "isolated" or not "phased" ?? I have no idea what that means. I've been told all grounds have been checked, polarity has been checked, all components have been tested with multiple meters, and all keeps pointing back to the TV. I had cable for years with my old TV, never experienced any problems. ALL started with the new TV at beginning of April. The cable box "whirrs" when it's not recording anything, and is off (except clock, and is always very hot to the touch.)I have to turn it off and on multiple times before it quiets down. The hard drive is what is burning out on the box. Thanks!!!! I hope I've answered the questions.
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post #15 of 39 Old 07-05-2011, 09:12 AM - Thread Starter
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More info, the HDMI cables were $99 each are the 'Chocolate' brand that are gold plated.
Several types of cable wires have been tried, but no difference.
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post #16 of 39 Old 07-05-2011, 10:35 AM
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You still haven't tried component cables yet? Sure would be in your benefit to confirm or eliminate HDMI interfaces of the TV or cable box.

Have your turned off the Anynet feature on the TV?

Just do the "easy" stuff first and see if you can diagnose/eliminate the issue(s).

And BTW... you spent WAY too much for an HDMI cable.
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post #17 of 39 Old 07-05-2011, 09:08 PM
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freemsuz:

Thanks for the update on your situation; I was wondering if you were going to come back.

I think you should try Ratman's idea. It will help you find out if there is a problem with the TV or the cable box, or both. It might be necessary to substitute another small TV for testing.

If you must use HDMI, I assume that you know that HDMI connections are not hot-swappable. This means that when you are connecting HDMI cables it is a good idea to have the equipment turned off and the AC plugs out.

If you can not measure it, you can not improve it.
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post #18 of 39 Old 07-06-2011, 06:01 AM
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Actually, it's a good practice to remove power when any cable is installed or removed.
But... most times, (myself included) we're just too lazy to take that precaution.
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post #19 of 39 Old 07-06-2011, 11:42 AM - Thread Starter
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Thanks, I was told that the HDMI cables don't have to be that expensive, but that's what the store sells you, and makes you believe it's necessary for HDMI. What are component cables? I'm afraid I don't know the difference.......I only have this one new LED 240hz 3D TV, so I can't test another TV, but the one I replaced never had any problem with the cable box, but it was a large, older big type TV. All of the hookups have been done by the Geeksquad or the Cable Co. themselves, or the electrician. I can only hope they know what they're doing, although they say the other doesn't have a clue. I'm a typical, electric-gadget challenged woman..........
I bought a 3 prong extension cord, and have plugged the surge protector (and all components) into another outlet. Since I'm getting a good picture, DVR, and the new box is working, I'm going to wait to see if it burns out. It wasn't humming when I checked it. The next step for Best Buy is to replace the whole TV, and I don't want to deal with that unless I absolutely have to. I bought a 2 year "Black Tie" warranty and it's only been 3 months, the other box burned out in 5 weeks.

thanks all!!!!
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post #20 of 39 Old 07-06-2011, 11:47 AM - Thread Starter
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Oh yeah, they tried turning off the anynet feature, but that didn't do the trick. I guess that's been an issue. I'm not the first one with this problem, the Cable Co. says it's a real problem with new TV's. Why doesn't someone make a small, voltage filter to put between the HDMI cable and the Cable box??? IS that possible?

thanks again.
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post #21 of 39 Old 07-06-2011, 12:32 PM
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Quote:
Originally Posted by freemsuz View Post

What are component cables?

http://www.monoprice.com/products/pr...seq=1&format=2

Quote:


Why doesn't someone make a small, voltage filter to put between the HDMI cable and the Cable box???

Because it is not necessary?

As for "store bought" HDMI cables, they mark up for profit, you can get the same HDMI cable for much less.
http://www.monoprice.com/products/pr...seq=1&format=2
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post #22 of 39 Old 07-06-2011, 01:18 PM - Thread Starter
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How do they get away with charging $99 each if you only need $4.00 ones?
I was literally told that the ones I got were far superior. It always pays when you know 'stuff' about 'stuff' doesn't it!!!

Thanks again, I'll check out those component cables.
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post #23 of 39 Old 07-06-2011, 01:38 PM
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Quote:
Originally Posted by freemsuz View Post

How do they get away with charging $99 each if you only need $4.00 ones?

Because they prey on the uninformed and can make a great profit. They give you a "deal" (sale) on the TV or audio system and make it up by leaps and bounds by selling accessories.
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post #24 of 39 Old 07-06-2011, 01:47 PM
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Oh, I see you are a woman, that answers so many questions... joking

I hate it when I hear someone paying that much for HDMI cables, grossly overpriced! If you can take them back do so and purchase your cables from monoprice.com, as Ratman suggested. You will have the same quality picture at one tenth the price you paid.

As far as checking the polarity, this basicly means that you are checking to see if the wires are backwards in the electrical outlet. If you are plugging your components into multiple outlets, and one outlet is wired the opposite of another this causes the polarity to be reversed. This will cause major damage to your components if they are connected together with an HDMI cable.

In another forum, one individual had a very similar problem as you are having. He had purchased a new TV and hired an electrician to install a new electrical outlet for the TV. Most of his equipment was fried once his new TV was plugged in. He called the electrician who came over and found nothing wrong with the wiring. After much discussion with others online the individual purchased an $8 tester to check the outlets in his home. This is when he found that the polarity was backwards in one of his outlets.

I had the same problem. The electrical outlet in my office was wired backwards. Everything in my office worked fine and I had no problems. My office adjoins my living room and I wanted to view my computer on my TV in the living room. I decided to run an HDMI cable to the living room and connect it to my TV. Of course I shut down all components and turned off my surge protectors while I did my wiring. Once everything was connected I turned on the surge protectors and POP!! It fried several pieced of equipment. I purchased the $8 tester and found the problem right away. It is very simple to read and I went through my entire house testing all the outlets to make sure the rest were wired correctly.

If all of your components are plugged into the same outlet, you should not have this problem.

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post #25 of 39 Old 07-06-2011, 02:36 PM
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Quote:
Originally Posted by freemsuz View Post

Why doesn't someone make a small, voltage filter to put between the HDMI cable and the Cable box??? IS that possible?

It is difficult. All 19 lines would need to be protected. Any practical surge protective device will have some effect on the signal. And it doesn't take much to make the signal on the TMDS lines unusable.
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post #26 of 39 Old 08-13-2013, 01:10 PM
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I am a satellite installation supervisor. I have ran into this too many times. The Samsung TV is the problem. The newer models use voltage to communicate with the surround sound systems so when the tv is turned on the surround automatically comes on. We teach our techs not to hook up to the HDMI1 slot. Most TV's that have this feature use HDMI1. I dealt with the issue today and it was a Samsung causing the issue. It actually fried the receiver. Hope this helps.
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post #27 of 39 Old 11-22-2013, 09:14 PM
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I deal with this issue everyday as a senior technicians for a big cable company. Voltage will cause tilling, box reboots, modem reboots in another room, missed recordings, ect ect. The reason it attacks the cable boxes is because the coax acts as the ground source since by law it must be grounded. We techs cannot fix it but there is a way to divert the voltage. What you need first is to verify that the power outlet is connected properly. The fast way is to buy a 5 dollar polarity tester. What you are looking for is that you have a proper ground and the right polarity. Next you will need a grounded power strip with the two coax tips on it (the one with the three prongs and the two tips that look like where the cable connects to the back of the tv). Third you will need a piece of coax cable. Not that cheap stuff, just as a cable guy for a jumper.

So what we are trying to do is give the voltage the path of least resistance. So you plug in the power strip to the working power outlet. Next you take the coax cable and screw it in the back of the tv on one end and the other to the power strip tips. It does not matter if its the in or out but let's use the in. That's it. If you check it before and after you will notice the voltage gone.

Now, not all power strips are created equal so some may work some may not. We started to test some on the field and when I can I will update you guys.
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post #28 of 39 Old 11-23-2013, 06:46 AM
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Welcome, DiabloC13!

Essentially what you're saying is that the problem is due to wiring faults with the AC mains power. That can be lethal! Clearly there's something very wrong if raw AC is found on a low voltage cable like HDMI. Scary that it's a normal thing for you to find! And it's not the fault of any brand of TV either.

I'm a veteran apartment dweller, so my advice for anyone who's renting (and for cable techs who go to rental units) is to take a problem like that to the landlord. Rental agreements and local laws vary of course, but in general interior wiring is the domain of the landlord. Renters and vendors should not take it upon themselves to do repairs themselves, no matter how small. Technically the landlord could use any DIY repairs to wrongly blame the tenant for the bad wiring, and it could get very costly. If you're a homeowner it's a different story. If you own it, it's your choice how to fix it.

I think it's only fair to mention that cable TV systems often use a DC voltage (~90V) that's used to power downstream equipment. And IME that DC voltage doesn't always get blocked off when it enters the customer's premises. So that's two possible paths for high voltage to get into the customer's equipment. And if that source is the cable TV cable, then the cable TV provider is the responsible party if anything gets damaged. IJS

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post #29 of 39 Old 11-23-2013, 05:58 PM
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No, I dont think its an apt issue. More of a defective tv issue. I see it more on the newer tv's under three years old. I quote Rabbit....The newer pieces of equipment use switchmode power supplies that produce more leakage current than the older equipment that used conventional transformer power supplies. Up until now no manufacture has spoken of any recall or free repair. To me Rabbits post is right in the money. My new tv out of the box was back feeding. So test them before you take them home.
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post #30 of 39 Old 11-23-2013, 07:30 PM
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Quote:
Originally Posted by Speed Daemon View Post

Welcome, DiabloC13!

Essentially what you're saying is that the problem is due to wiring faults with the AC mains power. That can be lethal! Clearly there's something very wrong if raw AC is found on a low voltage cable like HDMI. Scary that it's a normal thing for you to find! And it's not the fault of any brand of TV either.

I'm a veteran apartment dweller, so my advice for anyone who's renting (and for cable techs who go to rental units) is to take a problem like that to the landlord. Rental agreements and local laws vary of course, but in general interior wiring is the domain of the landlord. Renters and vendors should not take it upon themselves to do repairs themselves, no matter how small. Technically the landlord could use any DIY repairs to wrongly blame the tenant for the bad wiring, and it could get very costly. If you're a homeowner it's a different story. If you own it, it's your choice how to fix it.

I think it's only fair to mention that cable TV systems often use a DC voltage (~90V) that's used to power downstream equipment. And IME that DC voltage doesn't always get blocked off when it enters the customer's premises. So that's two possible paths for high voltage to get into the customer's equipment. And if that source is the cable TV cable, then the cable TV provider is the responsible party if anything gets damaged. IJS
It is equally important to mention that here on the internet you are very likely to see partial truths and gross misinterpretations such as this. Cable TV line equipment is powered by up to 90 volts of nearly square wave AC. This power is blocked at numerous locations so for it to 'leak' would imply the simultaneous failure of several components. While possible, it is statistically unlikely. In nearly 30 years of CATV work I have never seen that as a cause. Improper or poor bonding is much more likely.
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