Sounds like a ground loop. If you have a VCR or Cable box connected to the TV, try disconnecting it to see what happens.
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Clueless new guy needs help
I'm a new user here, and have a few basic questions. I've just buily my HTPC, and have had a few problems. I have a feeling I know what they are, but I though I'd ask here as well just to make sure.
Here are the specs on the box I'm using as my HTPC :
Asus A7V333 Mobo
Athlon T-Bird 1.4
256mb PC2100 DDR RAM
GeForce4 mx440 (Latest det drivers)
Hauppauge WinTV-PVR-PCI (model 880)
120gig WD HD (5400 RPM)
175gig WD HD (7200 RPM, 2mb Cache, not installed as of yet)
WinXP Pro
Onboard Sound (have a SB Live! card, just haven't installed yet)
Now, I got it all set up and running, but I'm having problems with the quality. I have an older RCA TV that its hooked up to right now, which I figure is one of the problems. I had to convert the S-Video from the GeForce to RCA, which I figured would mess with the quality a bit.
I'm getting horizontal bars rising up and down the screen, which is the big problem I guess. My first guess was the resolution (I was running in 1024x768) so I changed it to 800x600 (80hz), but the bars stayed. After reading some of the FAQs and not being able to find this problem specifically, I though it best to post. My best guess is that I'm either running the output at to high a refresh rate, and it should be at 60 or lower, not 80. The only other thing I can think of is some sort of interference, either on the conversion or near the card itself. I'm not an expert at things like that, so I'm not sure what could be causing the interference, or what specific things I should look for.
I had somewhat of the same problem on another machine with a Radeon 7500, it just wasn't nearly as bad.
The only other thing I can think of is it being the TV. Its an old RCA TV (not sure the model #, I'm not at home right now), but it doesn't take S-Video in. Could the RCA conversion knock the quality down that much???
I was hoping to run DVDs off this box as well, but I was thinking I might get better quality on the picture if I run the s-video into a standalone DVD player and let it do the conversion to RCA for me. Would this be a better option???
Again, I'm really new to this stuff, so I might have missed a usefull post somewhere here that would have helped me with this. If I did, just let me know, and I'll look harder for it. If not, any help would be appreciated!!!
Cheers
- Wader
Here are the specs on the box I'm using as my HTPC :
Asus A7V333 Mobo
Athlon T-Bird 1.4
256mb PC2100 DDR RAM
GeForce4 mx440 (Latest det drivers)
Hauppauge WinTV-PVR-PCI (model 880)
120gig WD HD (5400 RPM)
175gig WD HD (7200 RPM, 2mb Cache, not installed as of yet)
WinXP Pro
Onboard Sound (have a SB Live! card, just haven't installed yet)
Now, I got it all set up and running, but I'm having problems with the quality. I have an older RCA TV that its hooked up to right now, which I figure is one of the problems. I had to convert the S-Video from the GeForce to RCA, which I figured would mess with the quality a bit.
I'm getting horizontal bars rising up and down the screen, which is the big problem I guess. My first guess was the resolution (I was running in 1024x768) so I changed it to 800x600 (80hz), but the bars stayed. After reading some of the FAQs and not being able to find this problem specifically, I though it best to post. My best guess is that I'm either running the output at to high a refresh rate, and it should be at 60 or lower, not 80. The only other thing I can think of is some sort of interference, either on the conversion or near the card itself. I'm not an expert at things like that, so I'm not sure what could be causing the interference, or what specific things I should look for.
I had somewhat of the same problem on another machine with a Radeon 7500, it just wasn't nearly as bad.
The only other thing I can think of is it being the TV. Its an old RCA TV (not sure the model #, I'm not at home right now), but it doesn't take S-Video in. Could the RCA conversion knock the quality down that much???
I was hoping to run DVDs off this box as well, but I was thinking I might get better quality on the picture if I run the s-video into a standalone DVD player and let it do the conversion to RCA for me. Would this be a better option???
Again, I'm really new to this stuff, so I might have missed a usefull post somewhere here that would have helped me with this. If I did, just let me know, and I'll look harder for it. If not, any help would be appreciated!!!
Cheers
- Wader
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No box/VCR connected to it, I've got the cable line pluged from the wall into a splitter (so that I can still watch TV while getting it set up and tweaked) strait into the PC.
Its not just with TV that the quality looks bad, its also playing back movies directly from the HD as well.
I'm going to be installing powerstrip when I get home to dumb down the refresh rate to 60hz, from what I've read thats pretty much the optimal setting I think.
I'll see if the quality improves by unplugging the cable to the tuner though, thanks for the tip!
Its not just with TV that the quality looks bad, its also playing back movies directly from the HD as well.
I'm going to be installing powerstrip when I get home to dumb down the refresh rate to 60hz, from what I've read thats pretty much the optimal setting I think.
I'll see if the quality improves by unplugging the cable to the tuner though, thanks for the tip!
The cable line itself is more likely to cause a ground loop than a cable box. It is caused by the fact that the cable company ground is at a different level than the ground in your house where you have your PC connected. The cable ground could be physically hundreds of yards away.
Long term you might want something like the jensen ground isolator (Google Jensen Ground Loop). As a quick cheap short term test you can take two 75 ohm to 300 ohm transformersand connect the 300 ohm sides to each other (i.e. hook 300 ohm lead "1" from ytansformer "a" to lead "1" ytansformer "b" and the same for the "2" leads). This will give you a crude 75 ohm to 75 ohm isolation transformer. Plug the cable into one end and your splitter into the other. It may even be good enough for long term use.
Long term you might want something like the jensen ground isolator (Google Jensen Ground Loop). As a quick cheap short term test you can take two 75 ohm to 300 ohm transformersand connect the 300 ohm sides to each other (i.e. hook 300 ohm lead "1" from ytansformer "a" to lead "1" ytansformer "b" and the same for the "2" leads). This will give you a crude 75 ohm to 75 ohm isolation transformer. Plug the cable into one end and your splitter into the other. It may even be good enough for long term use.
I have no idea what most of that stuff is, lol, but now I have more research to do. Thanks for the info!
I'm not sure where the cable groud is, but I believe its just over 14 feet away from where the connection enters the house. I had a cable repair man over the other day, there was a small nick in my line about 6 feet from my house which was possible causing some problems with my internet service. The cable is not burried deep, and its only 14 feet from the house to the next connector. I'm not positive if its ground there, but I think he mentioned something about it.
Either way, thanks again, I got some more reading to do and hopefully I'll be able to try it out tonite. I'll test it without the cable plugged in first to see if that could be possibly causing the problem
I'm not sure where the cable groud is, but I believe its just over 14 feet away from where the connection enters the house. I had a cable repair man over the other day, there was a small nick in my line about 6 feet from my house which was possible causing some problems with my internet service. The cable is not burried deep, and its only 14 feet from the house to the next connector. I'm not positive if its ground there, but I think he mentioned something about it.
Either way, thanks again, I got some more reading to do and hopefully I'll be able to try it out tonite. I'll test it without the cable plugged in first to see if that could be possibly causing the problem
Nothing I've tried has worked.
Just to clarify, the bars aren't positional, they are rolling. Not sure if I gave anyone the wrong impression, but they're basically white bars rolling up the screen. I lowered hte refresh rate to 60hz and unplugged the cable.
Anyone else have any other suggestions??? I'm out of ideas now
Cheers
- Wader
Just to clarify, the bars aren't positional, they are rolling. Not sure if I gave anyone the wrong impression, but they're basically white bars rolling up the screen. I lowered hte refresh rate to 60hz and unplugged the cable.
Anyone else have any other suggestions??? I'm out of ideas now
Cheers
- Wader
It still sounds like a groundloop issue. If it is, here is a quick and dirty explanation:
-Your TV and computer are being grounded to different potentials. It doesn't take much a difference...less than a volt can do it.
-The cable connecting your computer to your TV will carry a 60Hz signal from the AC across that small potential difference.
-Your TV thinks the computer is telling it to scroll bars up the screen.
Groundloops are generally solved one of two ways:
1) Remove any grounding path between the two items with something like an isolation transformer.
2) Provide a much more conductive common ground between the items by plugging them into the same outlet or connecting their chassis with a fat wire.
Try this for starters before you pull your hair out:
-Disconnect *everything* from your TV and computer.
-Plug them both into the same wall socket.
-Run your signal cable from computer to TV
If you are still getting rolling bars, then your problem is not groundloop. If the problem went away, then move your PC back to where you originally had it and plug it into the wall there. Test again. Next, start plugging things back into your TV and PC one at a time until the problem reappears.
Once you find what device or combination of devices/connections is causing problems, tell us, and we can give you advice on various ways to solve the problem.
-Your TV and computer are being grounded to different potentials. It doesn't take much a difference...less than a volt can do it.
-The cable connecting your computer to your TV will carry a 60Hz signal from the AC across that small potential difference.
-Your TV thinks the computer is telling it to scroll bars up the screen.
Groundloops are generally solved one of two ways:
1) Remove any grounding path between the two items with something like an isolation transformer.
2) Provide a much more conductive common ground between the items by plugging them into the same outlet or connecting their chassis with a fat wire.
Try this for starters before you pull your hair out:
-Disconnect *everything* from your TV and computer.
-Plug them both into the same wall socket.
-Run your signal cable from computer to TV
If you are still getting rolling bars, then your problem is not groundloop. If the problem went away, then move your PC back to where you originally had it and plug it into the wall there. Test again. Next, start plugging things back into your TV and PC one at a time until the problem reappears.
Once you find what device or combination of devices/connections is causing problems, tell us, and we can give you advice on various ways to solve the problem.
Quote:
FYI: THe 75 - 300 ohm transformer is usually a little round thing ~ 2" long and .75'" diameter. It's got a coax connector on one end and a piece of flat antenna wire on the other. Normally you use it when your antenna has a 300 ohm impedance and your TV 75 ohm (or the other way around) in matches the impedance. It's actually a little high frequency transformer and it also isolates the inputs from the outputs (i.e. the ground circuit is interrupted). You will usually find one thrown in with every TV or VCR you buy or you can get it at Radio shack for a dollar or two. They may also be called baluns.
By connecting them back to back, as I suggested, you end up with something that connects to a 75 ohm coaxial cable on both ends and also isolates the input from outputs. The Jensen unit I suggested is a higher quality and will work over a broader range of frequencies. The jury rig setup I explained should work at least for VHF frequencies but it may not do too good a job at passing some of the higher cable frequencies. You can try it and see if if clears up your problem on the VHF frequencies. If it does and you need something better for the higher cable frequencies splurge for the Jensen (~$50).
Ground loops are impossible to predict and can be tricky to track down and fix. EricN's procedure is great. I jumped to the conclusion it's your cable because cable is a notorious cause. It doesn't matter where your cable is grounded or appears to be grounded, a tiny potential difference in grounds (even millivolts) can cause bars on video or hum on audio.
| Originally posted by Wader I have no idea what most of that stuff is, lol, but now I have more research to do. Thanks for the info! I'm not sure where the cable ground is, but I believe its just over 14 feet away from where the connection enters the house. I had a cable repair man over the other day, there was a small nick in my line about 6 feet from my house which was possible causing some problems with my internet service. The cable is not burried deep, and its only 14 feet from the house to the next connector. I'm not positive if its ground there, but I think he mentioned something about it. Either way, thanks again, I got some more reading to do and hopefully I'll be able to try it out tonite. I'll test it without the cable plugged in first to see if that could be possibly causing the problem |
By connecting them back to back, as I suggested, you end up with something that connects to a 75 ohm coaxial cable on both ends and also isolates the input from outputs. The Jensen unit I suggested is a higher quality and will work over a broader range of frequencies. The jury rig setup I explained should work at least for VHF frequencies but it may not do too good a job at passing some of the higher cable frequencies. You can try it and see if if clears up your problem on the VHF frequencies. If it does and you need something better for the higher cable frequencies splurge for the Jensen (~$50).
Ground loops are impossible to predict and can be tricky to track down and fix. EricN's procedure is great. I jumped to the conclusion it's your cable because cable is a notorious cause. It doesn't matter where your cable is grounded or appears to be grounded, a tiny potential difference in grounds (even millivolts) can cause bars on video or hum on audio.
Awesome, thanks for the tips and hopefully I'll be able to try all that out tonite!!!
Cheers
-Wader
Cheers
-Wader
If the default output is set to 80hz, it will still output it but only display it at 60hz, correct??? Thats what I thought was the problem, it was trying to pump it out at too high a frequency. I always thought it would send the signal however you had it set up, and then either convert it or simply knock it down before it gets displayed.
The refresh rate settings only affect the VGA/DVI outputs on your GF4, not the TV-out (S-Video or Composite RCA)
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