Electronic Interference?

[sai351]

Im currently running tv-out via an s-video cable and standard audio cables (red & white). Both are 20ft in length and are just some generic cables I picked up at Radio Shack. When I view my pc on tv theres always these faint white bars that roll up the tv screen. It's especially noticeable on a black background. Also, when I hook up the audio cables I get a loud 'humming' noise from the tv.
When I use the same cables from my dvd player, which is right under my tv, to my tv they work just fine.
I have tried separating the cables from any other cables which might be causing any interference and still got the same thing. I called radio shack, circuit city and best buy and they all said pretty much the same thing. It sounds like the interference is coming from my computer outlets and I should try a Monster Clean Power Surge Protector. So I went down to circuit city and they sold me a monster power home theatre powercenter HTS 700, which has a stage 1 v2.0 filter. I hooked it up to my pc and still had the rolling bars and humming noise! I even tried hooking it up to my tv and got the same thing. However, when I used the clean power the humming didn't seem to be quite as loud but the picture looked the same.
I ran an s-video setup in my previous apartment w/o a single problem. Although I was only running 12ft cables.
Anyone have any suggesions?

[bmwracer]

Try using the shorter cables and see what happens. You might need more heavily shielded cables, especially on the audo.

PCs radiate a lot of electrical noise and not just through the AC power lines. If your PC is not a store-bought model, it might not have FCC Class A(?) certification, which allows for home use and guarantees(?) non-intereference with other appliances.

[redwudz]

The source of interference like that can be tough to locate. I have had it coming from a computer before. I run 25ft cables from my HTPC KB, mouse and monitor, but never had any interference. I do have a 25ft S-video cable I use occasionally with my laptop with no problems. None of them are 'Monster' or similar overpriced brands. Radio Shack likes to push Monster products because they get an incredible markup on them. The quality is not that good compared to a good brand cable like Belkin. Don't get taken in by their hype. On the other hand, inexpensive RS cables are usually crap. Do yourself a favor and find a decent mail order source for cables.

For the computer, if that's the source of the noise, make sure the outlet it uses is properly grounded. If you have cable TV hooked to the computer, check the grounds on that also. My local cable is noisy and has ghosts on some channels that they apparently can't fix. You might want to try temporarily locating your computer a few feet from your TV and using short S-video and audio cables to rule out the long cable run as the problem. If the computer turns out to be the source and you are using a internal TV tuner card, that may be the problem. Some cards have a tuner that isn't properly shielded. The audio hum just sounds like a bad cable or poor connection. That should be easier to fix than the video problem. Again, testing with short cables may help isolate the problem. Filtering is OK, but it's better to eliminate the source of interference instead of trying to filter it.

[BJ_M]

these faint white bars that roll up the tv screen

is probably a ground loop - though not really a good idea , try bypassing one of the devices ground pin or use a ground loop isolation video device ..

[edDV]

these faint white bars that roll up the tv screen

is probably a ground loop - though not really a good idea , try bypassing one of the devices ground pin or use a ground loop isolation video device ..

I agree that ground loop is the problem. Solution is to power all the equipment from the same circuit breaker or isolate the connection with a humbucker isolation transformer (expensive), use an optical connection, or go wireless.

To prove ground loop is the problem, run a long extension cord back to the source and plug your TV into the extension cord. If the hum goes away that is the problem.

http://www.elect-spec.com/video_z.htm Hum Buck transformer.
http://www.dbugman.com/humbuck.html

BTW, if the interference ran horizontally it would more likely be video interference from a free running device like a VCR with no input or a DVD player.

[lordsmurf]

A humbucker for $50 is really not all that expensive, in the right context. Thanks for the link.

[Steve Stepoway]

To prove ground loop is the problem, run a long extension cord back to the source and plug your TV into the extension cord. If the hum goes away that is the problem.

Be certain to use a heavy duty extension cord. If you don't, you might get enough voltage drop across the extension cable to cause problems. I know, as I just fought that problem with A/V equipment at my church.

Steve

[vhelp]

I thought I'd respond with my own two cents worth, plus a bit of
my own personal history with noise and such things. The member
here, might actaully be having the same problem as I am. read on..

To get at the root of this "ground loop" thing, you have to be able to
identify it first. You gotta know that what you have *IS* ground loop.
Then, you work on resolving it. In this case, no sense on assuming what
it might be, until sai351; say's otherwise (via sample image) etc.

If what sai351; has, is what everyone seems to be in agreement of, ground
loop, he needs to to be certain of this. We can only speculate.

I think that sai351; should post a sample image (or video, even better) of
this "electrical interference". I was thinking of posting a short video
clip of what was noted earlier in another post here, regarding the white bars.

Then..

Here is my take on this ground loop and what can (or can not) be done about
it. If it is determined that it is ground loop, (tired of typing) I think that
the next step would be to see if it is removable. Some aran't.

My Analog Cable line, whenever I hook up my: VCR; DVD RECORDER; etc. to my
computer and capture card(s) and any of the units when connected to the Analog
Cable line, will result in these While Bars floating up/down my screen. Usually,
they go up the screen, not down. And when I remove the calbe from the unit,
guess what ?? You got it! The bars go away!

So, in my case, I have:

A) Determined I have noise in my video when connected to Analog Cable line.
B) Only when my Cable in connected to my units and my capture card, results in noise.
C) When I remove Cable line from units/devices (while capt card in use) noise is gone.
.. .. (reconnect cable, noise is back)
D) Because the noise is from my Cable line, there is nothing that can be done,
.. .. because this is my Provider's fault, and even though they have been back
.. .. to my house and service the Cable and Filter (is based on radio frequencies)
.. .. with new Lines and Filters, the noise is still present. This tells me that
.. .. the problem is even greater.. for it is a grounding problem anywheres in
.. .. the spider web of Cable, running from street to street, house to house, etc.
.. .. And, when you live in a comlex full of cable tv's, you can't isolate and
.. .. remove the trouble.

I have since, learned to live it with. What *I* do, is let my units record the
video source, w/out the units being connected to my pc. When I do this, there
is no noise. Then, I take the recording (tape or dvd disc) and bring that to
my pc. The dvd disc is the easiest to do, because there is no need for any such
connection to my capture card. However, the vcr tape presents another problem,
because even though I have recorded onto it w/out noise, once I connect the VCR
to my computer, guess what, haha haha, the noise is back. But its not
the same noise as the Analog Cable lines. It's the noise I've been suffering
from, for many years, to no avail. Anyways.

I just felt like putting some good words of experience up for reading. You never
know who might be having the same problem as mine.

Good evening, everyone.

-vhelp 4075

[ronnylov]

There is a device to insulate the cable-TV ground from the antenna cable. This is recommended if you have ground loop problems with central antenna systems or cable TV network. Perhaps you can try something similar?

Sheath current filter "coaxial", or mantelstromfilter:
http://www.hama.de/portal/articleId*23114/action*2563

EDIT: Hmm, I think this may be the same thing as the "humbuck" mentioned earlier.
Here are some similar products:
http://www.jensentransformers.com/iso_vid.html