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Trying to repair an amplifier

Discussion in 'Troubleshooting and Repair' started by dreamspy, Apr 4, 2013.

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  1. dreamspy


    Apr 4, 2013
    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.

    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:

    Brown stuff that leaked from the amplifier inside the subwoofer:

    Detailed view of the brown stuff :)

    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?

  2. dreamspy


    Apr 4, 2013
    Btw... is this the right forum for asking this kind of a question?? Is there some other forum you guys would rather recommend?
  3. duke37


    Jan 9, 2011
    The brown gunge has come from overheating the transformer. I do not understand why the thermal fuse did not blow. The transformer is now probably dead. Disconnect all secondaries and see if the fuse still blows or better, use a lamp limiter.

    The overheating could be caused by faulty rectifiers or capacitors so you will need to check these.
  4. sheldonstv


    Jul 17, 2007
    good chance the transformer has had it-check the power supply section for faults
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    It doesn't look as if the transformer has lost very much wax, and it looks to be in good condition - from the outside, at least. It might still be alright. As Duke suggested, disconnect all the secondaries and apply mains. If the transformer is OK, the problem is probably downstream from it - maybe the rectifier diodes or the capacitors, but it could also be a failure in the output stage of the amplifier.

    It's possible that the output stage quiescent current has been steadily (or intermittently) increasing due to one of many types of faults in the amplifier, and this would have overloaded the transformer, causing it to overheat somewhat and drip wax. If the fault has suddenly become permanent, the transformer will draw far too much current and blow the fuse.
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