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Ampeg sb-12 crackling

Discussion in 'Amps [BG]' started by glketterer, Nov 10, 2013.

  1. glketterer

    glketterer

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    My early 60s ampeg sb-12 makes a crackling noise when played at low to mid volume. Its all original except for the speaker( I kept the old speaker for the next owner). It has 12ax7s and 7686 tubes. Should I replace tubed or caps.


    gerry
  2. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Typically an amp of that age will need to be recapped. Your problem could be caused by almost anything. Tubes, resistors, leaky coupling caps even dirty tube sockets or a failing solder joint. As you are asking this question I assume you have little experience in trouble shooting a tube amp. If this is the case it's time for a tech visit.
  3. JimmyM

    JimmyM Supporting Member

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    Disclosures:
    Endorsing: Ampeg Amps, EMG Pickups
    Ya, caps were my first idea, although I've also had tubes do that when they go bad. If you have a spare tube of each, try replacing each tube one at a time till you find a culprit. If you don't, then best to take it to a tech so you don't spend money on not fixing it.
  4. beans-on-toast

    beans-on-toast

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    In addition to all of the above, the early SB-12 had the speaker connection in the two side latches. Make sure that the wires connecting to the latch are tight, and that the latch is clean and and that it mates tightly to the lid when closed.
  5. glketterer

    glketterer

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    The speaker connextions are good. Ill reseat the tubes and check for cold solder joints. I don't have any spare tubes. Then I will order a set of caps. thanks for the reply.
  6. beans-on-toast

    beans-on-toast

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    Fortunately a 12AX7 is relatively inexpensive and if you buy one you can try it in both positions (preamp, V1, and phase inverter, V2).

    You might find some helpful info here.

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