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Help! Cable TV hum!

Discussion in 'Archived Threads 2001-2004' started by Damon W, Mar 21, 2002.

  1. Damon W

    Damon W Extra

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    Well, I finally had a reason to hook up my cable - I wanted to watch the NCAA tournament. To my surprise, as soon as I screwed the coax cable onto my VCR, I started getting a constant hum in all of my speakers and subwoofer - and my VCR wasn't even turned on yet! The hum occured when ANYTHING from the VCR was connected to the amp (audio or video).

    How do I get rid of the hum? Is the coax in the wall too close to a power run...or is the problem elsewhere?

    Thanks in advance!

    P.S. Receiver is a Denon 3802 if that helps.
     
  2. Mike Matheson

    Mike Matheson Second Unit

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    Damon,

    I had the cable company come back out and make sure the cable was properly grounded. They assured me in advance that it was. One look though and they realized it wasn't. Ten minutes later my hum was gone.

    I previously tried using the two radioshack parts but ran into problems given I've got digital cable.

    There are some more expensive isolators around ($75-$200) which I'm told do a GREAT job.

    But it might be cheaper to call your cable service and indicate a "problem". . .

    Good luck,

    M
     
  3. John Morris

    John Morris Guest

    Mike: Damon has given some very good advice. Get the dang cable company to fix the problem. Sounds good, but in my experience, we seem to know MUCH more than their repairmen do. Still, have them check the cable ground. If they insist it is correct, then you might try one of my suggestions. The first one costs $6.82 or so and the home built one costs slightly less. I do not have digital cable, so I have not tried the Holland unit with that.???

    Sorry I couldn't be of more help!
     
  4. Damon W

    Damon W Extra

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    Thank you very much for the advice...I'll call the cable company first and if they can't help, I'll try the isolator.

    Thanks again!

    - Damon
     
  5. DavidSegelstein

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    Will the traps and isolators work with satellite coax? I have a hum when I connect the coax input to my HDTV satellite receiver to anything - either the coax from the dish or the coax termination on a surge protector. Do they only work for cable TV and OTA antennas?
     
  6. Sankar

    Sankar Second Unit

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    David,

    I have not had very good luck with isolators in eliminating hum issues with my satellite feed (DirecTV). I first built my own by putting an appropriate capacitor inline and later purchased the Mondial "MAGIC" isolator. In both cases, while the hum was eliminated (since the ground loop was broken), so were about half the channels !!

    Finally, it was a combination of physically grounding the cable and using a Monster HTS2500 that solved my problem.
     
  7. DavidSegelstein

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    Thanks, Sankar. Interesting about grounding. I'd also been thinking I may need to add a ground from the satellite receiver. Sounds almost sacreligious, but maybe that's the answer. I'll try it this weekend.
     
  8. ScottAndrew

    ScottAndrew Stunt Coordinator

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    I got cable installed and my subwoofer immediately began to hum whenever the cable touched my television. The cheater plug didn't work, but the solution in John Morris' second picture above worked perfectly. The Radio Shack part numbers are 15-1253 and 15-1140 or 1140B.

    Scott
     
  9. Sankar

    Sankar Second Unit

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    I wonder if anyone has had success using the twin transformers ("Radio Shack" solution below) with a satellite feed? I was successful using this for my cable (which I had prior to getting my satellite) and antenna (which I still have) feeds, but in my case it did not pass the Directv satellite signal unaltered. With the satellite feed, pretty much every solution I tried cut out the signals from about half the transponders (without the isolators I'd get a signal strength of around 80-90, which would drop to 0 with the isolator in series)! I tried the transformer (yes, I shopped around with a multi-meter to verify that the ones I finally got had total shield isolation) and capacitor style solutions shown here. As indicated in my earlier post, even the Mondial MAGIC box did not work ...
     
  10. Rob Jo.

    Rob Jo. Agent

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    John or anyone else,

    do you know where to buy the Holland isolator? I got the hum with digital cable too.

    thanks,

    Rob
     
  11. John Morris

    John Morris Guest

    Hi Rob: I don't know if the Holland unit will work for digital cable, but it might be worth a try. I get them locally at Electrotex. You will have to call them as the part does not come up on their online search. It costs under $7 each but I don't know how much they'll charge you for shipping. If they have trouble understanding what you want, just tell them it is on a rack close to the service counter with the rest of the cable/satellite stuff. Worse case scenerio, I could pick one up for you and send it to you if necessary.
     
  12. Rob Jo.

    Rob Jo. Agent

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    Thanks John, very much appreciated. I'll get in contact with them later today.

    Rob
     
  13. Jeffrey Chin

    Jeffrey Chin Second Unit

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    i witnessed the exact same problem, except i have comcast digital cable. i have it connected to my replaytv as well. save yourself time and headache by buying one of these babies. problem solved.
    3 words:
    MONDIAL MAGIC BOX
    http://www.audioadvisor.com/store/p...20TV%20Isolator
     

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