Ground Loop Questions and Problems

[mike1961]

Hello - I have a ground loop problem where I'm getting rolling video up my screen. I have 2 WinTV 500 cards and 1 WinTV 150 card in a new server I'm trying to set up.

I have a few questions:

1. If one has a ground loop problem, will it show in any tuner card or only some?

2. If I get an Isolation Transformer to fix the problem, can I get just one and then hook a splitter between then transformer and the 3 tuner cards on the computer or do I need a transformer for each of the 3 cards?

3. Any good links for a good isolation transformer?

4. Is the Hauppauge WinTV 500 a good card? I read mixed reviews a while back.

Thanks,
Mike

[SHS]

Hmm ground loop problem dosen't cuases rolling video
ground loop dose cuases Hum bar, Audio Hum and sometime RF Interference
Hum Bars: The mains frequency (50 Hz or 60 Hz) can cause stationaly or moving horizonal humming bar to appear on the video signal. If you have light dimmers nearby those humming bars can easily become quite severe and easily become move visible.

To test it hook cable up to TV set and using S/Video output from your Video card and set blue or black background.
See Attached Screenshot below
Check out http://www.hometech.com/video/atten.html it may be a cheap way or getting you cable guy out and see he has and isolator
Update if want best word has it that this where to look http://www.jensen-transformers.com/ but it going cost you and arm & leg

[Ken C]

Sounds more like a video card setup problem, wrong frequency setting perhaps ?

Ken C

[mike1961]

Yes - here's the situation.....I am referring to the file server which has 3 tuner cards in it. I am trying simply for now to test everything on the file server so I'm watching TV with Sage on the computer and not a separate TV. I checked the settings, Advanced, Monitor and it says the video refresh rate is 60 Hertz. I tried changing it to 75 and it still has the problem. I even tried another graphics card and it still says the monitor is between 60-75 hz. If I have this problem on the main server then (as I have checked) when it streams the data to any workstation or TV it's going to still have that rolling effect of waves going up the screen. How can I fix this problem? I've tried a pci express video card as well as a pci card in my file server.

Thanks,
Mike

[waynedunham]

Originally Posted by mike1961

I checked the settings, Advanced, Monitor and it says the video refresh rate is 60 Hertz. I tried changing it to 75 and it still has the problem. I even tried another graphics card and it still says the monitor is between 60-75 hz. If I have this problem on the main server then (as I have checked) when it streams the data to any workstation or TV it's going to still have that rolling effect of waves going up the screen. How can I fix this problem? I've tried a pci express video card as well as a pci card in my file server.

What are you using for a monitor, and at what resolution? Unless you're going very large on the resolution most monitors should support a higher refresh rate up over 80-85 hz. Many people can see the refresh (i.e. flicker) at rates as high as 70-75 hz while other people don't notice it at 60hz.

I wouldn't think it would effect whatever you're viewing the files on, that should be a function of what res/refresh you're running that at, not what the server is running. Many people are running servers with old video cards that can't even handle viewing the recorded video, just good enough to use the Sage interface.

[mike1961]

SHS - the "hum bar" jpg attachment you displayed is kind of like what I'm seeing. It's like a horizontal bar that flows up the screen...several at a time. I'm just using a standard pc flat LCD screen display. The default is 1024x768 but I've tried changing resolutions and it makes no difference. It's only when watching TV that I have this problem (not in windows XP or any XP programs...only when watching TV. I don't have any dimmer switches. I tried unplugging my cordless phones also with no luck. The problem is that this is happening on the file server so I can proceed any further until the file server has the best signal possible. I'm thinking about pulling out the 2 Hauppauge WinTV 500 cards and testing it with only the WinTV 150 card to see what happens. Isn't there something else I can do to fix this problem?

Thanks,
Mike

[mike1961]

Does anyone think if I try and get an ATI card or some other card instead of the Hauppauge tuner, I may not have these problems and I might have a more clear picture?

Thanks,
Mike

[stevech]

hum bars from ground loops usually happen because a video source (A) is connected to a video destination (monitor, recorder), via composite or S-video or other copper connection (not RF), AND... A is on one AC mains power phase and B is on another phase. This happens if A and B are distant from one another.

If A and B are both connected to your cable TV coax, there is some chance of a ground loop if the coaxes are not well grounded at a single common point, usually the residence's service demarcation point.

Hum bars can also get into long runs of coax - S-video, composite, etc. But again, a long run may imply different power phases as above.

Hum bars can happen because of a faulty power supply in some device.

Rolling bars that look like hum, sort-of, can be crosstalk between two video coaxes where each is carrying different video and the difference in vertical rates causes the rolling bars

Hum bars due to power phase differences and a ground loop can usually be eliminated by putting a 1:1 transformer in the video coax - marketed as "hum buckers". These cost $100 or so and degrade quality.

[mike1961]

More information ....I decided to put the tuner cards in my other computer in the same room and also tried using different tuner cards and still the same problem. So, I know it's not the computer. I then tried running the cable from the Digital Cable Box directly to the computer and "presto" no scrolling vertical lines. However, without the digital box, I get the lines. What does this mean? I am currently using the Freq Shifter so that Sage will tune the channels without snow everywhere but I still get what appears to be like rolling vertical bars going up the screen. However, I have now discovered that I only get them when I don't use the cable box. I still don't have the exact frequencies because my cable company for some reason says they don't know them or who to pass me to. I'm about to cancel it all and go to satellite but in the meantime is it yet another freq issue or something else?

Thanks,
Mike

[SHS]

Mike unless you solve your electrical problem you not going get rid the problem by going to satellite I know I have very some problem with cable and satellite which has difference problem.
But the other day my brother want hook his old Compac AMD K2-450 and I be dran the monitor started having rolling vertical bars even change out the power supply and 2 difference monitor didn't help but as soon I take over to my brother buddy house it didn't have that problem so my step is try hook on other power phase on other end of the house to see that help.
I have funny felling that part of my problem is at main power transformer being part of what stevech just said being if one of two 110v power phase difference from each other that most likey that where the power problem is at becuases that mean it be difference then cable power phase which dosen't match.

[mike1961]

SHS - wanna bet? I just discovered that I'm having the same problem on my TV set (no computer) without the cable box. I think when my cable co. switched to digital they did something and I'm having the same interference on regular TV. Now I know the problem is not in my computer at all.

That makes 3 problems now my cable company has not resolved or addressed along with one tech being rude to me. Why are we so loyal? I'm switching to satellite today.

Thanks again everyone for this forum and the help.

Mike

[mike1961]

SHS - have you tried testing it on a regular TV and bypassing the entire computer? I was quite shocked to find that all the problems on the computer went away when I went through the cable box and then I was absolutely floored when I bypassed the cable box and hooked the cable directly to my TV set and I saw rolling bars right on the TV. Now I know it's the cable itself.

ONE QUESTION THOUGH ---> I noticed that when I hooked it into my computer through the cable box, the very top line of the screen looked fuzzy (only the top line). I tried adjusting the overscan to move the screen up but it would not go away. Any ideas why? I remember reading another post a while back about this but I can't remember where or the replies.

Thanks,
Mike

[sleonard]

At your breaker box there is a ground wire going to a long spike driven into the ground. There is also another ground where the cable comes into the house. If these two grounds are far enough apart it can cause a small phase difference between the power outlets and the cable system causing a ground loop and the rolling lines. The solution (in this case) is to move one of them so that both are attached to the same ground spike. There are a number of other causes for ground loops as well. Try going to AVS forums and searching for "ground loop". There was an exhaustive post about a year and a half ago that thoroughly covered the causes and solutions if you can still find it.

[mike1961]

But wouldn't I see the rolling lines when I watch TV through the cable box as well? As far as I can tell, the cable ground is grounded directly to the main power breaker at the house.

Thanks,
Mike

[SHS]

Yes mike I can see on TV with anything else hook but was bit pain try get screenshot of it that why I did with Windows Desktop on TVset.
Not really mike being the cable box act as an isolator.
I have look in to one sleonard and I like know that post when to as well sleonard.
Update to this

But the other day my brother want hook his old Compac AMD K2-450 and I be dran the monitor started having rolling vertical bars even change out the power supply and 2 difference monitor didn't help but as soon I take over to my brother buddy house it didn't have that problem so my step is try hook on other power phase on other end of the house to see that help.

Put the PC on otherside of the house it didn't have that problem.

[mike1961]

SHS - I do have the cable tech person coming out in two days. But, in the meantime, you are suggesting that the cable box is acting as an isolator. So, is it possible for me to pick up an isolator somewhere in my area here? Does radio shack or some other electronics place have them? I'd like to get a good quality signal. Do you believe there is still a ground problem somewhere?

Finally - when I do go through the cable box, everything looks good except like the very top line on the screen looks fuzzy (just the top line) and I'm not sure why.

Thanks again,
Mike

[mike1961]

The cable tech person came out today and replaced the connectors to the end of the cables at the box. Also, I noticed that there were two splitters at the box (a jumper from one splitter to splitter #2). The ground wire was connected to splitter #1 rather than the main feed. I think that may have been the problem because he connected the ground to the main feed and also changed the connectors. The problem with the rolling bars is now fixed.

However - I do notice on my computer monitor (not sure about regular TV yet) that when I view small numbers on the screen (like the score of a football game for example) they seem a little fuzzy compared to just watching it without Sage on a regular TV. Is it my computer hi res monitor 1024x768 that does this or something else? How can I fix it?

Thanks,
Mike

[sleonard]

Originally Posted by mike1961

#2). The ground wire was connected to splitter #1 rather than the main feed.

Glad you solved your problem.

The fuzziness on text may be due to de-interlacing done by the computer. Computer monitors are progressive scan devices that require interlaced sources to be de-interlaced but even the best de-interlacing leaves artifacts. When viewed on a regular TV no de-interlacing occurs because TV's are not progressive scan devices. You're seeing a native siganal played back in it's native format.

[SHS]

That or native broadcast it self being he said on top which is usly in overscan area and sleonard has a point about de-interlacing.
As for the isolator the cable guy should have one.
When say main feed are you ref to main ele ground rod?.

[mike1961]

So you are saying that when I hook the TV up to the computer through the graphics card, the numbers will be more clear? It's strange in a way because on the one hand the computer monitors are a lot more clear when viewing computer text such as from a word processor but you are saying that when viewing number from a football game or something it will be more clear on the TV?

Thanks,
Mike