Ampeg BA210 Blowing Fuses

Discussion in 'Amps and Cabs [BG]' started by cwsbass, May 18, 2012.

  1. cwsbass


    Mar 28, 2012
    First timer here.
    Hope someone can help me.
    My Ampeg BA210 blow the internal fuse recently.Replaced it ,same thing.
    Had a look at the boards and noticed two of the ceramic resistors on the power amp board were cracked.Replaced them,same problem.
    Looked into it on various forums and it seemed the mosfets could be broke.
    Replaced them.YES.Amp powered up.
    I am now getting a lot less volume and fuzzy distortion.
    Im no electronics expert but can handle a soldering iron.
  2. BassmanPaul

    BassmanPaul Inactive

    MOSFETs are not BJTs and cannot simply be replaced. Each bank of MOSFETs needs to contain matching devices. The bias for the output stage has to be set to a suitable level.
  3. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    This is a job best left to a qualified amp technician. You need more than a soldering iron to repair an amp.
  4. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    A tech is best..... You seem to have a bias problem. There might be some added problem besides the bad outputs. It is relatively rare for mosfets to be bad and no other part is also bad.... I would first suspect the 4 resisitors of 47 ohms which are near the mosfets, but other parts might also be bad.

    It could also be that the bias is just way off, and only needs to be adjusted. To do that you need a good DVM, and some added knowledge.

    And to know which scenario is the true one you need the knowledge and experience.

    By the way, the 210 uses the IRFP140/9140, which we didn't have matched/grouped. Only the IRFP240/9240 were matched/grouped. At some point I believe we switched over to get the matching.
  5. cwsbass


    Mar 28, 2012
    Thanks to everyone for your help.
    Will get this in to a tech this week.
    Just thought I would have a try myself first.
    Thanks again.
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