Amplifier repair - burned coil..?

Discussion in 'DIY Corner - Tips & Techniques' started by dreamspy, Apr 4, 2013.

  1. dreamspy Enthusiast

    dreamspy
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    Hi there

    I have a subwoofer with a built in amplifier, and recently the amplifier seems to short-circuit and usually blows my fuse almost immediately with allot of electronic noise coming from the amplifier a few milliseconds before.

    The amplifier that I have is an M-Audio BX10s. I just opened it up and there seems to be something brown has leaked out of the big coil, but has now hardened. You can see this better in the following pictuers:

    Location where the leakage occurred from the amplifier:
    http://i264.photobucket.com/albums/i...y/IMG_0565.jpg

    Brown stuff that leaked from the amplifier inside the subwoofer:
    http://i264.photobucket.com/albums/i...g?t=1365069414

    Detailed view of the brown stuff
    http://i264.photobucket.com/albums/i...y/IMG_0564.jpg

    I'm wondering if this looks like something I can fix myself, maybe by changing out that coil? Or do you guys recommend taking this in for repairs?

    regards
    Frímann
  2. Speedskater Audioholic

    Speedskater
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    The links didn't work. Links sometimes don't like getting copied from other posts.

    Coils don't burn-up by themselves, something else is toast.
    It's probably a Class 'D' amplifier, which are hard to fix.

    Look up 'light bulb tester' and 'dim bulb tester' they save on blown fuses when troubleshooting.
  3. j_garcia Audioholic Jedi

    j_garcia
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    The only thing that typically "leaks" inside an amp are the capacitors. Get their values and replace them.

    The transformer "coil" does not usually burn or leak, but if it got hot enough that it DID melt the coating on the winding, then I would probably not try to repair that myself because it would seem to indicate something pretty seriously wrong.
  4. Missionman Junior Audioholic

    Missionman
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    id put my money on transistors...

    I once has a QSC Pa amplifier, which used to trip one channel out past a certain volume..
    Opened her up, weakened and damaged solder joint, giving intimant connections on the PCB, causing the Transistor to blow...

    In a sub, it could also be a possibilty, especially with all that air pushing inside the cabinet, can quite easily help damage a solder connection over time of heating and cooling...

    But +1 to the dimming bulb to troubleshooting.. i used either a 35w or a 20w bulb, concidering what im working on, and a ACVAC, variable voltage regulator, so i can run amps at lower voltages while troubleshooting, and then slowly turning it up to full power slowly, making sure everything is ok..
  5. Ampdog Audioholic

    Ampdog
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    As above.

    Perhaps just a hint on the slowly turning up of mains voltage plus bulb practice. Very good, only some amplifiers are not exactly stable at too low mains input and might oscillate, drawing considerable current. Keep in mind while turning the mains input up. (If you also have an oscilloscope ....)

    Sorry for late reaction; did not notice the thread earlier.

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