Ground loop?

[Ghost]

Alright.

I've had my Cable box hooked up to my plasma for months, never had a problem.

I got a receiver 2 months ago. Cable box went to receiver. Receiver to TV. No problems

LAst week i hooked up my brothers xbox to the Receiver. I got these odd lines going across the screen, in various postions, and various sides. they dont move, and you can only notice them when its not bright.

Now, im new to all A/V. But I did some quick reading and ground loop made sense.
Except I cant seem to figure out what is going on.

I have a backround in electronics, so i happened to have a multimeter.

I tested the voltage between the grounds on different equipement. Voltages were crazy.

I unplugged everything, and started testing things 1 at a time.

Between Xbox ground and receiver ground, i get 17 volts AC.
Between The CoaxCable ground and the Tv's ground. 60 volts.
Between Cable box (with coax unplugged) and TV. 12Volts.
Between Cable box (with coax unplugged) and Reciever. 50volts.

Etc Etc Etc. Nothing seems to be grounded properly.
Now no matter what if i send any video through the reciever, i get these lines.
Though, it depends on what signal i am sending to it, and how many other things are plugged in. The lines can be so faint you can barely notice them, or so visible you want to stab your eyes out.

I mean i am honestly confused, as to what is causing so much difference in potential on different grounds.

The appliances with 2 prong plugs are the ones with the highest voltages on their respected grounds. 50-60volts.

But from my reading on ground loops, they should rarely exceed 5-10volts.

So what in gods name is happening.

Any help would be greatly appreciated.

EDIT. They are all plugged into to the same outlet. There was a router as well on that outlet, but i disconnected it before testing, to make sure the ground problem wasnt being caused by all the cat5 cables.

Edit #2. I was just thinking, i havnt tested my outlets eath ground. I dont know if it is grounded or not. It should be. But who knows, my house is falling apart lately. I wont be able to test that for a day or so do to time, and having to climb into my attic. But, could this cause such insane grounding problems.

 

[mtrycrafts]

two things to do:
run a copper ground wire to each components chassis and see what happens to the image.
if that doesn't help, use this on the cable TV coax to the receiver:
http://www.cencom94.com/gpage.html8.html

 

[Alamar]

Could you plug in most of the electronic equipment into a single decent surge protector and then just get some sort of isolator on the cable input???

I would think that would eliminate any potential for ground loops if all the equipment is either isolated or share a common ground [through the surge protector].

EDIT: Also make sure that all of the grounds in your various outlets are actually grounded properly. Something doesn't quite add up to get a 50V difference in grounds.

P.S.: I'm a newb so what I have to say may not mean anything

 

[Haoleb]

Im not really sure how you were measuring those voltages but they are dangerously high. Alot of components have the earth ground tried to chassis ground so there should be no potential between those points. Pick up one of those outlet testers at lowes or home depot that you plug into a receptacle for problems. They are 5 bucks.

 

[dorokusai]

I have an HT room that has outlets wired in series...or is that parallel?

Anyways, I had a viscious ground loop that I didn't find until I installed my surge arrestor and it wasn't happy. I pulled all the outlets and found 1 out of 7 was wired incorrectly. Rewired, problem solved.

I hope your issue is that easy. Ground loops can be a PITA. Check your outlets with the VOM.

Mark
Polk Audio CS

 

[mtrycrafts]

I have an HT room that has outlets wired in series...or is that parallel?

Anyways, I had a viscious ground loop that I didn't find until I installed my surge arrestor and it wasn't happy. I pulled all the outlets and found 1 out of 7 was wired incorrectly. Rewired, problem solved.

I hope your issue is that easy. Ground loops can be a PITA. Check your outlets with the VOM.

Mark
Polk Audio CS

What was wrong with the outlet wiring?
While the outlets follow each other in a circuit, it is wired in a parallel fashion

 

[jcPanny]

Video problem

Is the video problem only with the X-box source? If so, connect the x-box directly to the TV and see if it has the same problem. If so, try the x-box on another TV. This will help identify if the problem is the x-box or the receiver video output.

You can get a $2 tester at the local home center that will tell you if the hot, common, and neutral are wired correctly on your outlets.

 

[dorokusai]

What was wrong with the outlet wiring?
While the outlets follow each other in a circuit, it is wired in a parallel fashion

Ok, parallel it is but it was running a hot to my ground connection.

Mark

 

[Haoleb]

Ok, parallel it is but it was running a hot to my ground connection.

Mark

Are you sure it wasnt the neutral. If a hot was shorted to ground the breaker would just trip and if that didnt happen you probably woudlnt have a house to live in.

 

[Johnd]

What was wrong with the outlet wiring?
While the outlets follow each other in a circuit, it is wired in a parallel fashion

Well, from dorokusai description, actually not mtry.

A parallel circuit in home wiring is tantamount to a homerun...a dedicated circuit. An outlet is wired in series when they are connected to each other, that is, the hot and neutral of one outlet is connected to the hot and neutral of the next, and so on.

 

[dorokusai]

Are you sure it wasnt the neutral. If a hot was shorted to ground the breaker would just trip and if that didnt happen you probably woudlnt have a house to live in.

I'm not positive as this was a couple years ago. It wasn't tripping a breaker, so you're probably correct about what was wrong.

Mark

 

[orAgon]

Well, from dorokusai description, actually not mtry.

A parallel circuit in home wiring is tantamount to a homerun...a dedicated circuit. An outlet is wired in series when they are connected to each other, that is, the hot and neutral of one outlet is connected to the hot and neutral of the next, and so on.

Actually that would be parallel, Johnd. If they were in series they won't work until ALL outlets in the series are in use. Cheers.

 

[Rickster71]

What you describe is quite possible; when you have high ground rod resistance.
It is one of the reasons Arc Fault Breakers were introduced.
If this is still the case, have your ground system checked.

As to the receptacle wiring question:
The gold star goes to whom ever picked parallel.
If devices were wired in series, and that outlet, or connection failed, the subsequent outlets on that circuit wouldn't work.

 

[mtrycrafts]

.. An outlet is wired in series when they are connected to each other, that is, the hot and neutral of one outlet is connected to the hot and neutral of the next, and so on.

Well, no, and well that is why I said they follow each other but wired in parallel. Sorry, but the wiring is parallel. I think you may be thinking that for parallel you need a home run from each outlet? If so, that is also parallel, yes and so is how homes are wired with a number of outlets on a breaker.
Series wiring is when the hot wire from the breaker goes to the first outlet hot terminal. then the negative(neutral goes to the next outlet's hot terminal.
Any wiring that allows the same voltage across the loads is in parallel.

Also
http://en.wikipedia.org/wiki/Series_and_parallel_circuits

 

[mtrycrafts]

Actually that would be parallel, Johnd. If they were in series they won't work until ALL outlets in the series are in use. Cheers.

And they would not have the same 120V across each load, not from a 120V breaker.

 

[orAgon]

And they would not have the same 120V across each load, not from a 120V breaker.

That would be due to the voltage drop across each of the loads.