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  • Solid state help

    I think I have some issues with the solid state portion of a tube amp
    ITs very early solid state reverb recovery and tremolo
    Sunn Sentura schematic heaven has the pdf if you have time
    to look at it,
    I was wondering what I can replace the 2n2923 and things with
    they are still made I guess modern versions
    THe reverb is very distorted and they use a transistor for recovery
    also the trem I am told does not work, maybe I can add some tubes
    to fix all these issues!
    Steve

  • #2
    It's just a basic amp stage, most any NPN small signal transistor will work.

    But make sure it is not something else. The circuit runs on +16.5VDC. Is that up to voltage and clean? A ton of ripple will certainly distort the output. Is the reverb pan OK?

    I'd use at least a 30v part. SOme potential parts: MPSA18, MPS8097, MPS8098, 2N5088, 2N4401, 2N3904, MPS2222. Lot's to chose from.

    I'd bet the trem problem is the opto.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      I have it apart now..

      The 16V seems ok I cant see it (no scope at the moment)
      one of the smaller caps 25uf looks bloated so I may change that,
      the reverb driver on the schematic I found is supposed to
      be a 12au7 this amp has a 12ax7 ? I have the sentura not the
      sentura II but I am thinking someone may have swapped it?
      The board is out and I am checking the transistors for shorts..

      Can that module be "made" or bought any where?
      Thanks Enzo for the reply always nice to have some help
      with the solid state I have some 4401 and 2904 around I think
      if not they are cheap enough..
      Steve

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      • #4
        Fixed trem and reverb shorted transistor

        I found some old 2n6008 transistors here and replaced one
        that was shorted it read zero ohms collector to emitter
        and it read that way out of the circuit as well..

        The cool thing is the old parts I found have that same weird
        looking flat side so, it looks all orig.
        and I dont have to replace that module... thankfully

        PS... IT think it is supposed to be a 12au7 I put in a 5814 from my stash
        and both the reverb and trem are woking great now

        Thanks

        Steve

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