Horizontal interference lines in TV-out

[whymetoo]

Hi,
Let's see if I can describe my problem clearly.

I got a new PC (motherboard P5AD2 DX) with a chaintech nvidia 6600 GT PCIexpress graphic card (Power supply 470Watts I think). I connected the TV-out to my TV via a S-video connector and I got horizontal interference lines climbing up the TV.

After some research I decided to disconnect everything from the TV except the TV-out from my PC. The interference lines disappeared. Then I tried to plug in separately (one by one) the different connectors and the all gave me interference lines. The video-in connector from the VHS, the cable and also the audio out that goes to my amp.

I tried something else also. Seeing that my DVD is connected the TV via an S-video connector I tried routing the signal through my amp. seeing that the TV only has 1 s-video slot. The DVD is OK but when I try the TV-out I get interference lines.

Can somebody explain to me why I am getting these lines and why me DVD is OK and not my TV-out from PC? Is it the signal strength?

Is there a solution to my problem?

Thanks in advance.
Pascal

[lordsmurf]

Sounds like herringbone, a power-caused noise.

[whymetoo]

Ok then is there a way of elimating the herringbone inteference. Signal bousting or grounding??

[lordsmurf]

Search the forum. I've discussed this in the past, as well as the coax filters I've used to correct it. Others have too.

[edDV]

Try powering the TV off the same wall plug as the PC.

[whymetoo]

I have the PC stuff connected to a power bar and the TV and home theater stuff plug into another power bar and both of these are pluged into the same wall outlet.

I tried something yesterday. I disconnected everything from the TV hook up the tv-out from PC and I didn't have any inteference (ie same as previously stated) I then connected the video out of my VCR to the TV and the inteference appeared on the tv-out connection. I then disconnected the cable-in of the VCR and the inteference disapeared.

If the inteference appears when I connect something to the TV the Tv is the problem. By connecting something to the TV is it causing some kind of grounding??

[jameshgross]

I suspect that you have a ground loop problem.
Make sure that the power sockets are properly grounded. Make sure that each unit is properly grounded.
Ckeck each cable for open shield.

How to check for ground loops - Take a digital multimeter but it on AC range. Check for a voltage between the units case and the ground pin of the electrical socket. If you read a voltage > then a volt you have a ground problem.

[whymetoo]

I will try it. I am no expert so I will ask you a question if you don't mind.

When you say between the units case and the ground pin of the electrical socket. then I un plug the TV or PC have one end of the multimeter on something metal of the PC and another on the groud pin or should the unit stay connect while I'm using the multimeter

thanks

[jameshgross]

Leave everything connected as normal. Measure between the case (exposed metal or screw head) to the ground on the electrical socket.

[whymetoo]

Took me some time. But I tried what you said and they were all under a volt. I tried a few a things and finally pined the problem down.

It's the cable. I have the main cable that is going into a 4 way splitter. The 4 out going cable are going to 2 TVs, a VCR and the PC. When I disconnect the TV and the VCR the lines disappear. When I reconnect either one of them they reappear. I then disconnected the main cable from the splitter leaving the 4 out going cables connected and the lines disappeared.

When I took a look at the main cable I notice that it had on the side a ground wire that was not connected to the house’s ground. I connected the wire but the lines are still there. Seeing that the ground wire on the cable and the cable itself are isolated one from the other it makes sense that it did not solve the problem.

Is there some thing that I can do about the cable to fixes the problem?
thanks

[whymetoo]

Tried a few thing on the weekend. 1st I noticed that grounding block for the cable in the basement and the main cable was not attached. I attached it and it improved the signal but the lines are still there.

I tried connecting the main 'grounded' wire directly to the TV and the lines are still there I also tried boosting the sighal but no changes. I am up to a point were I think I am going to fix the problem by have a cable switcher on the line that is going to the TV and when I want to view stuff from the PC that I am going to switch out the cable connection to the TV. I dont like doing this But I have a feeling that the problem is the main cable that I don't have much controle over.

If there any type of filters or stuff that I could try let me know.