Can somebody please give me the definition of a "ground loop". Here is what happened to me.
Installed a 60" LG plasma, right away I had I rolling horizontal line about 6 inches wide that changed the color of everything from green to a pinkish color.
Component out of reciever to component in on TV, HD sat and DVD component to reciever. This only showed up thru component, composite was fine. I went directly from TV to SAT, and TV to DVD, changed cables
it never went away.
Also, breaker to that circut triped twice while I was there. Related to problem?

The next day I went back out there, line was still rolling, changing colors, but not as bad.I brought a new 60' LG plasma, picture was perfect on all inputs,
thought problem was solved , today another tech went out on another unrelated problem, he said that the plasma was still doing the same thing, they could turn on a chandiler and the "problem" would show up, turn it off it was fine. I checked out first plasma at the store, no problem .

So what caused this problem? Why did it only show up on the component input? I thought a ground loop was a audio problem, somebody set me straight. (in a nice way)
Thanks in advance
CB1
How do you fix it, how to prevent it, is this out of my hands and is it a electricans problem now? (Larry)

This message was edited by cb1 on 12/19/03 22:51.

ground loops and hums can affect audio and video...

1) try removing the satellite receiver COMPLETELY from the system...disconnect it from the av receiver, the plasma, the power, everything...and see if your problem goes away...

2) You said the problem came and went with the powering up and down of the chadelier? is it a low voltage or dimmer controlled chandelier? is it on, for whatever reason, the same circuit as the plasma and audio gear? is it low voltage, with dimmer and IN CLOSE PROXIMITY, or any of the wires feeding it, to the plasma?

keep us posted, this one is interesting...

avdude

Most ground loops that I've seen have been caused by cable TV, and it shows up on everything.

I think we had the same problem with the 60" LG. They were gonna tske another one out there today, I'll have to find out how it went.

Let us know if you find the problem.

A good habit to get into is to only ground the receiver in your system, float all the other grounds, except for a sat dish or any other Lighting protected item. Use a cable TV ground isolator also.

Ohms most important law= "Current always follows the path of least resistance". When you have several potential paths to ground, you can develop strange osolations, from constantly changing voltage fluctuations, rapidly jumping from one path to the other. Having one path to ground forces discarded currents to flow in one constant direction.

I have found it is essential to have the display ac outlet and video source ac outlet be on the same ac circuit. This has solved most humbar problems. I have seen a Lutron dimmer actually make the humbar go up and down following the movement of the dimmer slide. Of course the customers 14 year old son pointed this out to me :)

It sounds like a noise issue to me, but you can check for ground loop. If your sat receiver has a three prong plug use a 3 to 2 adapter and replug it into the outlet. If the problem goes away you were seeing a ground loop. You will need an isolation transformer on the rf input to solve the problem. Do NOT leave the 3 to 2 adapter in, this is illegal and dangerous. Check out Jenson transformers on the web they have a lot of useful trouble shooting info,

We had a similar problem in a clients home recently, it turned out that the electricians had wired the circuit in such a way that there were "shared" neutrals being fed by two different cicuit breaker panels in the home. One the neutral problem was solved the problem went away. We also had a breaker trip problem on this circuit, when a particular light was turned on it would trip the breaker if the plasma was on but not trip if either load was on the circuit independently

A ground loop is two sets of ground paths from one component to another.
When you have two such ground paths, you can mentally envision these paths as a strange-shaped loop.
This loop is just the same as one turn of a transformer.
One turn of a transformer, in the presence of a varying magnetic field, will have a voltage induced in it.
We are used to thinking that audio and video inputs respond to the voltages that come in via the hot leads. In truth, they respond to the DIFFERENCE between any voltages on the HOT and GROUND leads. Therefore, if a voltage comes in on a ground lead, it will go into the system.

This is hum.

As audio, if it is just plain 60 HZ from power running through the house, it will, well, hum. If it is noised induced from a dimmer, it will sound like a buzz as there are lots of high frequnecies present due to the way the dimmer acts.

As video, since color video is not quite 60 Hz, this hum will manifest as two areas (one for the bottom of the sine wave, one for the top) that slowly move up the screen.

Look up Jensen Transformers for a complete ground loop and hum troubleshooting guide. They make transformers to isolate grounds so any such loop is broken, but their troubleshooting helps you understand the concept and see if there is any other way to solve the problem than to buy an isolating transformer.

this is ho ho ho humm
its christmas!!!!

God Bless Us Every One.

And, since this is the Digital Age,

God Also Bless Us Every Zero.

Another way to deal with this?

Determine which circuit breaker at the panel is for the outlet that the source equipment is on, as well as the breaker that the Plasma is on.

If these circuit breakers are one directly above the next, get an electrician to switch one of them so there is a circuit breaker in between the two you are using.

Sounds more like a phase problem to me...