Help with Video Card Standard Def TV Issue

[civerson4]

On my BTV Link machine, I am running a ATI 9250se card to an SD 32" Sony TV via S-Video. The Link machine is based on P4 1.7 Ghz running on an ASIS motherboard (can't remember the model). The video slot is AGP 4x.

Everything works great-with one exception. I have a very slow moving "band" that scrolls from the bottom of the TV set up through the picture and then starts over. The "band" probably takes 15 seconds to get from the bottom of the TV to the top--and it is 8-10" high as it scrolls (takes up about 1/3 of the TV screen). It is almost like a shadow or artifact on the TV--and is most noticable against a dark background. I don't really notice it with BM (default Bluewave Skin)--but I do with BTV...especially on "black" backgrounds when watching TV.

Any ideas what would be causing this or a possible solution? Thanks

[axarce]

I had this problem too. Very annoying. Believe it or not, I fixed it by using an S-Video cable with the gold plating on the connectors. 8 bux at Walmart. I did this over a month ago and only twice did that band pop up. But when it did, it was very faint and only went up the screen once. Then it'd disappear. I'm trying to determine if it's caused by something in the house kicking in like the freezer or laser printer.

[beerandchips]

electrical hum causes this issue. Make sure all power is coming from the same outlet or circuit location. good cables also help alot. This should cure your problems. Knock wood.

[civerson4]

Thanks for the help..the mystery continues however....

I was just watching a show on my server computer (BTV 3.5.2 [not Link] connected to a 19" LCD) and noticed the same scrolling "bar". This is a 3.0 P4, using an Nvidia 5200 via DVI to the LCD monitor. And both the monitor and server are running through an APC UPS. So I can't be the S-video cable on this system (I am connected via DVI) and the UPS "conditions" all the power....This is the first time I have noticed it on my server...

Any other ideas? Thanks.

[axarce]

Can you connect your tv signal cable directly to a regular television set to see if you may be having signal problems?

[EagleTG]

A few quick tips off the top of my head:

- Don't coil excess cabling.
- Run signal and power wires separately. Run power and signal wiring intersections at 90 degrees instead of running the wires parallel if they must be near each other.
- Use high quality cabling. (Edit, no need for "insanely priced" cabling, but use a decent grade. Something better than "freebie cable that was packed-in with my $30 DVD player".)
- If the band is "in" the recordings, then check your COAX wiring for faults/cheap cable. The local cable company that I use is notorious for using cheapo grade cabling.
- Are you using any signal amplifiers? They can cause this problem as well.
- Coax splitters, especially ones outside your home can go bad.

[not_Shorty]

this is pretty easy to fix actually. The problem is an electrical difference between your electrical ground and the ground on the tv signal cable from the cable company. It's solved rather nicely by getting two 75ohm/300ohm adapters and wiring them back to back.

There is one caveat, you have to get a specific type of 75ohm/300ohm adapters. There's not really any way to tell from the packaging either, you have to test it with a multimeter to see if it'll be good for this application. Put the multimeter in resistance (ohm) mode and touch one lead to the threads of the 75ohm side, and touch the other lead on the 300ohm side, first on one blade terminal and then the other. If you see a 0 ohm reading then you have to keep looking for a different brand/model. The 0 ohm reading means there is continuity there for a DC signal/current and that is more or less how the ground loop hum is getting through. Actually, it's ok if you use one adapter that shows DC continuity, but at least one of the two adapters has to show no DC continuity for this to work. So, find at least one 75ohm/300ohm adapter that does not show 0 ohms on the meter when you touch the 300ohm blades and the 75ohm threads with the meter's leads. Once you've found suitable adapters, throw one on the end of the cable coming out of the wall, and then connect it's 300 ohm blade connectors to the other adapter's 300 ohm blade connectors with some small screws/bolts and nuts. And then just connect the rest of your setup to the second adapter's 75ohm output, and viola, ground loop gone.

If you go here and scroll down to the bottom you'll see a little diagram of what I'm talking about. I'm using this solution here on my rig and it works beautifully. It's the section at the bottom titled "Transformer isolator using two baluns."

http://www.epanorama.net/documents/g..._building.html

[civerson4]

Thanks for the suggestions. I will give it a try--and post the results here soon. Thanks.

[RiderFan]

I had this problem too. I was using a RF Modulator and amplifier. My solution was simple, crude but effective. I would just reposition mod, amp and cables till it stopped. It took quite a while and looked goofy but it worked.

I have since changed my setup to a coolermaster case beside my TV hooked through S-Video and have had no problems like that since.

[not_Shorty]

repositioning won't help when it's a ground loop. You have to get rid of the ground loop. So if the problem is a ground loop, and it certainly sounds like it is, then just pick up a couple adapters like I suggested and it'll work out fine.

[merrypig]

Tip; make sure it's not interference from your vga video cable. Change your desktop frame rate and see if the width / rate of scrolling of the 'bands' changes. If it does, don't worry messing with ground loops. Move your cables apart or use better shielded ones.

Plus if you pause playback of the video and the bands still moves, it's interference ont he output side - if it freezes, it's on the input side. Also good to know and I think others alluded to that test above.

[not_Shorty]

any progress?

[civerson4]

Thanks for everyone's help....and I am sorry it has taken me so long to past an update.

I did install the transformer isolator with two baluns as suggested by not Shorty. This seemed to help--as did the fact that it appears at least one of my cable TV connections was "loose" where it screwed into one of my PVR 250's. I am testing it right now--and the problem appears to be solved, but I can't confirm whether it was a loose cable or the balun solution.

[not_Shorty]

pretty safe bet it was a ground loop and the isolator cured it. I've yet to see a single cable tv installation in my neck of the woods that didn't cause a ground loop with the house electricity main ground. Thanks for the update.