Rolling ascending lines on cable

Discussion in 'Archived Threads 2001-2004' started by Dave F, May 26, 2002.

  1. Dave F

    Dave F Cinematographer

    Joined:
    May 15, 1999
    Messages:
    2,885
    Likes Received:
    2
    This is starting to drive me nuts. On every TV in the house, there is a horizontal band that rolls upward while watching cable. I've had a similar problem after connecting my PC to a TV, which I cleared up by using better cables. It seems to be worse later in the evening, but that may just be a perception issue due to different light levels. Also, on the HDTV, the line is surrounded by a 1 inch band.
    I've had the Cable guy take a look at it, and he said it wasn't a problem with the cable. In his words, it wasn't "a hum line".
    So, now I'm trying to a determine if it's a problem with the cable, the electrical wiring, both, or something else entirely. The cable company is thinking I'm nuts (I've had 'em out here twice), and I can't seem to get anywhere. Help! What do I need to do to get this fixed?
    Thanks,
    -Dave
     
  2. Marc Rochkind

    Marc Rochkind Second Unit

    Joined:
    Aug 26, 2000
    Messages:
    381
    Likes Received:
    0
    Well, it's good to see that the HDTV displays the line a bit better than the analog TVs! [​IMG]
    Anyway, here's what I would do:
    1. Take one of the smaller TVs to a point near where the cable enters the house, or even outside, and connect it with a fresh piece of cable to the cable company's cable. It may or may not be accessible... you may have to be inventive.
    2. Turn off everything that's powered in the house, to make the power as clean as possible.
    3. Run a long extension to a neighbor's house, to get a new supply of electricity (just for the test).
    My guess is that it is in the cable that's common to all of the TVs, most likely at the point where the signal is distributed. Something is loose, wet, corroded, or whatever.
     
  3. Rachael B

    Rachael B Producer

    Joined:
    Jun 5, 2000
    Messages:
    4,687
    Likes Received:
    27
    Location:
    Knocksville, TN
    Real Name:
    Rachael Bellomy
    It sure sounds like current feeding back into the cable. If it isn't the cable company, it could be one of your TV's or VCR's. I had this situation in an apartment I used to live in and one of my neighbhors TV's was the culprit. The cable company cut off their service until they repaired or replaced the set. You should disconnect everything but one set and start adding stuff back and see what happens. Good luck!
     
  4. Rob Roth

    Rob Roth Stunt Coordinator

    Joined:
    Feb 1, 2001
    Messages:
    113
    Likes Received:
    0
    If you see about 3 or 4 interference bands on the screen at at time it is almost certainly 60 Hz AC power contamination. Check the grounding of the cable signal; usually it is best to have ground equivalence with the AC powering your system. Check also for an AC line in close proximity to your cable, induced EMF is a possibility. If all else fails I think there is some product (Magic something) that ISOLATES cable ground from house ground. If I remember correctly this is a product under $100.
     
  5. Dave F

    Dave F Cinematographer

    Joined:
    May 15, 1999
    Messages:
    2,885
    Likes Received:
    2
     
  6. Wayne A. Pflughaupt

    Joined:
    Aug 5, 1999
    Messages:
    6,061
    Likes Received:
    25
    Location:
    Katy, TX
    Real Name:
    Wayne
    Dave,

    This sounds like a ground loop, as Rob noted. The incoming cable signal should be grounded to the house electrical ground (i.e., the ground stake). If it is not grounded, or is grounded somewhere else, you can get a ground loop.

    To check this out, look for a “grounding block” at the point where the cable service enters the house. It looks like a regular splitter, except it has only one connection for in and out. There should be a wire attached to the grounding block that goes to the ground stake. Make sure the wire is secure at both ends.

    Regards,
    Wayne A. Pflughaupt
     
  7. Rob Roth

    Rob Roth Stunt Coordinator

    Joined:
    Feb 1, 2001
    Messages:
    113
    Likes Received:
    0
    Dave,

    If your cable ground is not connected to the ground cable for your breaker box, there can be a voltage difference between the cable box (and associated cables) and the rest of the system. The voltage difference can manifest as a 60 hz signal 'added' to your interconnect signals. On an O'scope it actually shows up as a band of noise on the bottom of the screen.
     
  8. Dave F

    Dave F Cinematographer

    Joined:
    May 15, 1999
    Messages:
    2,885
    Likes Received:
    2
    Thanks for all the tips, folks. I checked the grounding wire and it seemed a little loose. Ok, a lot loose. I tightened it a bit which made a significant difference, but didn't solve the problem. Since it seems like that is the heart of the problem, I'm callin' the Cable dood tomorrow to have him/her take a closer (and more educated) look at it.

    Thanks,
    Dave
     
  9. Michael Marklund

    Michael Marklund Stunt Coordinator

    Joined:
    Mar 3, 2002
    Messages:
    160
    Likes Received:
    0
    Dave,
    FWIW, I had a similar ascending line that crept up my screen every 10sec or so. Drove me nuts. It happened after I connected my digital cable box to my system using a s-video cable. I was trying out the s-video over coax to see which I liked better. However, for my test, I used a very cheap s-video cable (the one from my camcorder). When I switched to a very good/decent cable, the line was gone.
    Don't know if your using s-video or what, but maybe this is a quick something to try.
    Good luck,
    MM
     
  10. Drew_N

    Drew_N Extra

    Joined:
    Nov 16, 2000
    Messages:
    20
    Likes Received:
    0
    I had the very same problem I noticed when I got my HDTV. There is an easy and cheap solution. Parts Express (www.partsexpress.com) has a isolator that breaks the ground loop. I am using one and it works great...and its cheap at $12.
    Part number is: 180-075
    Direct Link
     
  11. Dave F

    Dave F Cinematographer

    Joined:
    May 15, 1999
    Messages:
    2,885
    Likes Received:
    2
    Thanks Drew, I think I'll give that a shot. I had the Cable Guy come over, but he would not believe me that the rolling lines could be related to the grounding. He tighted the connection to the grounding pole and it helped, but did not cure the problem.

    Could this be something that the electrician would have to fix?

    -Dave
     
  12. Reece

    Reece Stunt Coordinator

    Joined:
    Apr 3, 2002
    Messages:
    94
    Likes Received:
    0
    I found an even cheaper version of the same ground loop breaker herefor $7.00
    Go to the bottom of the page and look for xantech #63400
     

Share This Page