Ground Loop Issue With Cable TV

[JCW]

I just finished hooking up a stereo and TV in our guest bedroom. For some odd reason, I had a ground loop. After removing things one at a time (WI game, DVD player, CD Player, & TV), I discovered that the ground loop was coming from the cable TV. If I unhook the cable TV and leave the TV hooked up to the preamp and power amp, the loop goes away. Has anyone experienced this before?

We have this same cable system on our other TVs and there is no problem. I'll get back to it tomorrow, but I welcome any thoughts on it. I have reversed the polarity on every plug that I could. The next thing will be to start lifting grounds which I don't like doing.

Thanks

 

[Adam]

Hi. That seems to be fairly common, based on how many people bring it up here. I just had that same issue with my system last week. I'm using an antenna (not cable), and I recently put it outside and then got the hum. My solution was a simple one - a ran the cable for the antenna through my Belkin PF31D (it's a power conditioner/surge protector), and the hum disappeared. I figured that the Belkin would put the cable lines on the same ground as the electrical lines, and based on the results, I think that's what it's doing.

If you have a surge protector that also has inputs/outputs for a cable line, I'd suggest giving that a try. It worked for me, and my recollection is that it worked for someone last year when I recommended that they give it a try.

 

[mtrycrafts]

I just finished hooking up a stereo and TV in our guest bedroom. For some odd reason, I had a ground loop. After removing things one at a time (WI game, DVD player, CD Player, & TV), I discovered that the ground loop was coming from the cable TV. If I unhook the cable TV and leave the TV hooked up to the preamp and power amp, the loop goes away. Has anyone experienced this before?

We have this same cable system on our other TVs and there is no problem. I'll get back to it tomorrow, but I welcome any thoughts on it. I have reversed the polarity on every plug that I could. The next thing will be to start lifting grounds which I don't like doing.

Thanks

If you don't have a surge protector or one with a cable TV surge protector on it, try this or similar:
http://www.cencom94.com/gpage.html8.html

 

[highfigh]

I just finished hooking up a stereo and TV in our guest bedroom. For some odd reason, I had a ground loop. After removing things one at a time (WI game, DVD player, CD Player, & TV), I discovered that the ground loop was coming from the cable TV. If I unhook the cable TV and leave the TV hooked up to the preamp and power amp, the loop goes away. Has anyone experienced this before?

We have this same cable system on our other TVs and there is no problem. I'll get back to it tomorrow, but I welcome any thoughts on it. I have reversed the polarity on every plug that I could. The next thing will be to start lifting grounds which I don't like doing.

Thanks

It's not caused by a ground loop in your house, it's from the cable company. If you have a short coax cable, cut the end off, strip it so only the center conductor is sticking out and insert it into the cable box feed. The noise will probably be gone. If this is the case, go to Parts Express ask for a ground lift adapter.

 

[Rickster71]

The two grounds are at different potentials, (your house ground and the cable company's ground) however the coax cable will now be joining them together forming a loop.

There are electronic solutions to reduce the effects of a ground loop, however a single technical ground is a good starting point.

In a perfect world all grounds would be at the same potential however these days many electronics have input power filters each of which will leak a mA or more to ground and this all adds up. Another problem is where the ground and neutral conductors are connected at multiple locations – sometimes intentionally. This forces the local ground voltage to be the same as the neutral voltage.

There should be a grounding block where the cable TV enters the house. That block should be connected to the service ground. All those connections should be checked. I'd start with the ground in the guest bedroom.
The best short cut fix would be what Adam mentioned, next up the ground lifter that Mtrycrafts suggested.

 

[JCW]

Thanks guys for the great info. I'll follow up and get it worked out. It's amazing how many times I've done this over the years and never had this problem (even in this house). Regardless, it's here now and I'll deal with it.

Thanks again to all!

 

[tcarcio]

You can try a cheater plug. Take the plug from your cable box and get a two prong adaptor[cheater plug] plug the cable box into the adaptor and then into the wall.

 

[highfigh]

The two grounds are at different potentials, (your house ground and the cable company's ground) however the coax cable will now be joining them together forming a loop.

There are electronic solutions to reduce the effects of a ground loop, however a single technical ground is a good starting point.

In a perfect world all grounds would be at the same potential however these days many electronics have input power filters each of which will leak a mA or more to ground and this all adds up. Another problem is where the ground and neutral conductors are connected at multiple locations – sometimes intentionally. This forces the local ground voltage to be the same as the neutral voltage.

There should be a grounding block where the cable TV enters the house. That block should be connected to the service ground. All those connections should be checked. I'd start with the ground in the guest bedroom.
The best short cut fix would be what Adam mentioned, next up the ground lifter that Mtrycrafts suggested.

It can be caused by ground potential issues and in many cases, you can actually measure a lot of voltage on the cable when referenced to the equipment's chassis. The cable companies aren't big fans of grounding their feeds and on any jobs where I see this, I make them come out and fix it. It's not that hard to get action when the NEC rule is mentioned. When I still had cable, I disconnected the cable from the box and got a pretty good jolt, so I measured the voltage- >15V.

 

[Phil Taylor]

It's most likely a ground potential problem but just wondering if you do have a cable box and if so have you tried bypassing the box and running the cable straight into the TV - and if so is the hum still present? If that clears it up your cable box would be the source and need "attention".

 

[j_garcia]

Get this guy and try it: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=180-075 It worked for me. There is a whole thread on how to solve ground loop hum if you haven't reviewed it already. A surge suppressor WILL NOT solve this issue, as I have two of them and neither removed the hum from my system in my previous place. I called the cable company and they eventually got around to correcting the issue and that is ultimately what you need to do. It should be completely free too.

 

[Adam]

A surge suppressor WILL NOT solve this issue...

Granted, mine is a "power conditioner," but it DID solve my hum.

 

[Rickster71]

A surge suppressor will help, "if" it ties all the grounds together, as Adam's did.

The key here, is to have all the grounds tied together, and ultimately going back, and being bonded at the service entrance.

 

[Adam]

Rick et al,

Which part of the coax cable needs to be grounded - the sheath or the core? I was wondering if someone could simply connect a wire between the sheath and electrical ground (using the grounding screw on a receiver or surge protector, if available) to tie the grounds together and remove the hum.

Thanks!

Adam

 

[TLS Guy]

Rick et al,

Which part of the coax cable needs to be grounded - the sheath or the core? I was wondering if someone could simply connect a wire between the sheath and electrical ground (using the grounding screw on a receiver or surge protector, if available) to tie the grounds together and remove the hum.

Thanks!

Adam

That won't usually solve it. The current flows through the chassis causing the hum. Rickster is correct, grounds must be tied at residence entry.

If you have one ground you won't have hum, more than one you very likely will, it is as simple as that. It is the shield of cable systems that needs to be at ground potential and seldom is.

 

[Rickster71]

Rick et al,

Which part of the coax cable needs to be grounded - the sheath or the core? I was wondering if someone could simply connect a wire between the sheath and electrical ground (using the grounding screw on a receiver or surge protector, if available) to tie the grounds together and remove the hum.

Thanks!

Adam

Hi Adam, it is the sheath that gets grounded.
That's supposed to happen before the cable enters the house, at the grounding block.
Many times that block doesn't get installed, or the ground connections are loose, or corroded.

Rick

 

[highfigh]

It's most likely a ground potential problem but just wondering if you do have a cable box and if so have you tried bypassing the box and running the cable straight into the TV - and if so is the hum still present? If that clears it up your cable box would be the source and need "attention".

I've never see this problem caused by the cable box- it has always been from the cable feed. Usually, the ground outside and all of the homes being fed are the cause. To be honest, if more cable installations were done according to the National Electrical Code (Article 25, IIRC), we wouldn't be discussing this at all. The feed is supposed to be grounded at the point of demarcation using a proper ground stake or the drop from the meter box or immediately after entering the building, attached to the cold water supply BEFORE the water meter.

 

[highfigh]

Granted, mine is a "power conditioner," but it DID solve my hum.

Some of those have isolation for the coax and phone lines, which is why it removed the hum. I would bet that if you used a power strip with no protection but still ran the cable through your conditioner, the hum would still be eliminated.

 

[Shock]

You can try a cheater plug. Take the plug from your cable box and get a two prong adaptor[cheater plug] plug the cable box into the adaptor and then into the wall.

If you're talking about a 3-prong to 2-prong adapter they're illegal, against code and a fire hazard. If you were ever to have an electrical fire your house issurance would NOT cover it.

 

[highfigh]

Rick et al,

Which part of the coax cable needs to be grounded - the sheath or the core? I was wondering if someone could simply connect a wire between the sheath and electrical ground (using the grounding screw on a receiver or surge protector, if available) to tie the grounds together and remove the hum.

Thanks!

Adam

If the core is grounded, the signal will be shunted, and it will never reach your cable box or TV. It also causes problems for the cable company because the cable customers near you will suddenly call with problems.

On your second point- if the cable goes to several locations in a building and a splitter is used, the splitter has a ground screw, which is what connects to the ground point is a ground block isn't used outside. As long as the F connectors are snug, they're all grounded at the same point. That's the whole reason for structured wiring and all electrical/communications feeds being in the same location- grounding is much more effective if it can be centrally located. Long ground runs are less than optimal.

 

[mike_wassell]

Last summer I switched cable boxes. Originally I had the cable running through my Panamax surge protector/power conditioner. When the technician hooked up my new box he did not run the coaxial cable through the Panamax. I did not think anything about it at the time but started to get a pronounced hum from my speakers. It took me a week or two to figure it out but I decided to run the cable through the Panamax and the hum disappeared. The Panamax worked great.