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SVT mid-switch no worky

Discussion in 'Amps and Cabs [BG]' started by THB_bassman, Jan 10, 2006.

  1. THB_bassman


    Oct 11, 2005
    '73 SVT, mid-selector switch and /or the potentiometer that controls it does nothing.
    Amp was last known to be retubed and recapped in '97.
    I know, take it to a tech. But is it possible it could be a very simple thing that I could do? Not an electronics wizard, but more than reasonably mechanically inclined.
  2. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I hesitate to suggest opening it up, since there are lots of nice high voltages in the unit..... not good to get into without knowlege.

    If you do open it up, unplug it, and let it sit for an hour or so just to be safe before you start.

    In any case, almost any problem there could be will require some electronic troubleshooting skills.

    About the only thing that would not, is a knob problem, which I assume is not what you have.

    "no worky" has several possibilities..... not working right, not even changing the sound, etc.

    The coils have been known to go bad. The switch could have a problem. There could be a bad connection, a bad resistor or capacitor, the list goes on.

    There could even be a tube problem or socket problem.
  3. THB_bassman


    Oct 11, 2005
    Thanks Jerrold
    I believe I will open it up after doing as you say. I realize "no worky" is vague, but it just means that flipping the mid- select switch, while playing with the knob adjustment, does not change, even slightly, the sound produced. The rocker switch feels sort of soft, not like a new one would, I think wear is in there and I just wonder about the contacts.
    All the other (treble, bass, etc) switches / knobs work OK.
    Thanks for your post, any other idea are appreciated.
    There is no tech near me, and I would avoid it if possible just for the inconvenience factor.
  4. THB_bassman


    Oct 11, 2005
    I fixed it.
    The mid select coil had come unglued and fallen off the board, and ripped the 4 wires off the board.
    A little solder and super glue got it working.

    I will go back in and put in a long screw through the board, coil and a large fender washer and nut. That will prevent it ever happening again.