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Any ideas to resolve ground loop problem?

Discussion in 'AV Receivers' started by MartyP, May 5, 2004.

  1. MartyP

    MartyP Stunt Coordinator

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    I just bought a NAD T753 and have noticed that there is a hum when my television is on. When I turn it off the hum is gone. I disconnected the cable from my Monster Cable HTS1000, but the hum remained. I disconnected the interconnects from the TV to the NAD; again the hum remained. It is a problem when the input for TV or DVD is chosen and the TV is on. The hum comes from the speakers and not the receiver itself. With the TV off, there is no hum when listening to the DVD input. I know ground loops are common, but can anybody help me save what litle sanity I have left?
     
  2. NickGL

    NickGL Agent

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    for unpolarized 2- prong plugs, i've heard advice to merely turn the plug around

    play around with different plugs and see if it helps
     
  3. MartyP

    MartyP Stunt Coordinator

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    yeah, I don't have any unpolarized plugs. Still trying to figure out what's going on...
     
  4. Aaron Gilbert

    Aaron Gilbert Second Unit

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    Is your TV plugged into the same outlet as the rest of your system? It sounds as if you're saying there are now no connections between your TV and receiver, and yet the hum remains any time the TV is turned on? And yet, you only hear the hum if you are listening to the DVD or TV input on your receiver, none of the other sources? Am I correct so far?

    If so, it sounds to me like the TV is actually causing some type of interference with your DVD player. Are they close to each other physically? What happens if you leave the receiver on the DVD input (with hum present!) and then you turn off the DVD player? Are you using an analog or digital connection between your DVD player and receiver, or both? If both, do you hear hum even when using the digital connection (I would find this highly unlikely)?

    All that said, there's also the possibility that your receiver has a faulty input. Try moving the DVD player connections to another source on your receiver and see if the hum disappears or moves to that source. If the hum is gone, suspect the receiver. If it stays, suspect the DVD player.

    Good luck!


    Aaron Gilbert
     
  5. MartyP

    MartyP Stunt Coordinator

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    Aaron:

    Thanks for your reply. Yes the TV is plugged into the Monster Cable HTS1000 with the rest of the equipment, I tried to plug it into the wall outlet instead, but it made no difference.
    The TV and receiver are connected by two cables: 1) S-Video cable 2)pair of analog interconnects
    Yes I am using both analog (5.1 outs for DVD-A) and coax digital connections between DVD player and receiver. I do not get the hum when using the digital connection only (with the TV off).
    I'll try a few of the things you suggest...thanks for your reply.

    Marty
     
  6. Dean_S

    Dean_S Second Unit

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    DO you have cable tv??? It quite common for the ground loop to be caused by cable. Try disconnecting the 75 ohm cable from whatever device it's plugged into the test for hum again. If it stops then reply I'll tell you how to fix it.

    Does any of your electronics have a grounded plug or are they all polorized two-prong plugs???
     
  7. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Dean,

    Don't know about Marty, but I need that fix. My TV started humming when I connected a projector into the system that gets its power from another circuit. I can eliminate the hum either by unpluging the cable TV source coax, or by putting a cheater on the projector. Don't want to do either of these things.
     
  8. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Dean,

    Don't know about Marty, but I need that fix. My TV started humming when I connected a projector into the system that gets its power from another circuit. I can eliminate the hum either by unpluging the cable TV source coax, or by putting a cheater on the projector. Don't want to do either of these things.
     
  9. Mark C.

    Mark C. Supporting Actor

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    Seems as if most ground loops are caused by inadequately grounded cable or satellite TV sources. In fact, it seems most often that satellite causes more problems than cable.
     
  10. Mark C.

    Mark C. Supporting Actor

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    Seems as if most ground loops are caused by inadequately grounded cable or satellite TV sources. In fact, it seems most often that satellite causes more problems than cable.
     
  11. Chu Gai

    Chu Gai Lead Actor

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  12. Chu Gai

    Chu Gai Lead Actor

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