Expert Help Needed: humming problem

Discussion in 'Archived Threads 2001-2004' started by Vito_Jr, Mar 15, 2003.

  1. Vito_Jr

    Vito_Jr Extra

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    Hi,

    Want to feel good by doing something nice for someone? Help this poor bewildered imbecile with his humming problem (no jokes please).

    I have read all of the posts on the humming problem (from sub and pq problems) and have not been able to find anything. I've had my components (see below) checked out by an authorized repair service, I've had the electrician, cable co (comcast) and professional installers here together - no diagnosis. The last word from the installer was "dirty ac" and recommended a panamax surge protector/line filter. I hooked it up and there is still a hum.

    I've looked at "the usual suspects" as suggested here. But here is what I know:

    The hum appears only when I turn on my plasma. when I shut off, no hum.

    The installer said, along with a million other suggestions (sorry) that maybe the plasma is interfering with the receiver. Is this possible? Before you answer, I had the sysytem set-up in another room while the new room was being built. The plasma was left in the styrofoam packing material for a rudimentary floor stand (worked great by the way) and I had my receiver placed in front to the left of the panny stacked on a floor speaker with my other components. The point is that rather than being below the screen as it was almost at the top, but not higher, in the older room.

    I used the system for 2 months - no hum. Then a hum from the sub developed. Come to find out with all of the work the cable ground was disconnected. I told the electrician, he grounded it along with every splitter in the basement, and no hum.

    Then the new room was built, the system installed and the hum returned.

    Will someone tell me where to go with this? At this point I feel I am being passed around by the technicians I've had come in.


    System

    Panasonic 42PWD5UY
    Onkyo lsv-950 all in one dvd/receiverw/ powered sub
    Motorola digi cable
    jvc vcr

    Plasma is on its own circuit (as recommended by the installer) and the components on another. I have plugged the plasma into the same circuit via the panamax but the hum remains.

    Thanks for helping out.
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    What is humming? Your speakers or subwoofer?

    If it's the sub, how do you have the subwoofer connected? Do you have a coax cable with little arrows indicating the signal direction?

    The "subwoofer cables" are simply audio cables with one difference: the shield is NOT connected to the RCA plug at the destination end. This often eliminates ground-loops. The sub will take electrical ground as the zero-volt reference.

    You can also try a 2-prong to 3 prong "cheater" plug on the subwoofer power cord. This breaks ground loops as well.
     
  3. Vito_Jr

    Vito_Jr Extra

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    Bob.

    The sub has a 2 prong outlet. When the installer came back the 2nd time he said he called Onkyo and was told they recommend coonnecting the "drain" at the sub wall jack (not that I know what that means) He did that and we still had a hum. Also I have only one rca wire connected to my sub. I'll reverse the wire to see if that makes a difference.

    Thanks for responding - any other ideas in the meantime? What about "the plasma is interfering with your receiver" theory?

    Thanks
     

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