Star Amplfier problem

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by voxworld, Sep 9, 2006.

  1. voxworld

    voxworld Member

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    I just picked up a Gainstar 30 and it has an odd problem.
    When I play a G bar chord the amp crackles and has a pronounced static sound that changes levels.
    I changed out the preamp tubes and there was no change.
    Any opinions? Thx.
     
  2. kaseri

    kaseri Member

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    Something similar happened to me with my old 6545. I sent it back to Z and it ended up being a bad power tube socket.
     
  3. voxworld

    voxworld Member

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    Thanks for that, I'm leaning toward power tubes as being suspect. He specs for the Valve Arts EL34's, not sure who's selling them though.
     
  4. Fretts

    Fretts Member

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    If the whole amp likes to vibrate in the key of "G", it could be a cold solder joint or a resistor or other part that is reacting to the increased vibration. That could include connections at the tube socket, or also the guts of a marginal tube.
     
  5. voxworld

    voxworld Member

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    I was going to try some other power tubes but the tube retainers on the power tubes have a clamp around them that squeezes around the base of the tube with a screw.
    I removed the screw and bent out the clamp a little but the tube wouldn't budge.
    I didn't want to force it without being sure,
    Is there anything I'm overlooking in releasing the tubes froim these clamps?
    Also, this amp is billed as being 'true class A', can I just put in a set of matched EL34's and go?
     
  6. Jeff Flowerday

    Jeff Flowerday Member

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    Kevin, it's most likely cathode biased and not "True Class A". That said you can pop some tubes in safely. I like to check the bias anyway just to make sure the tubes aren't way too cold or hot.
     
  7. voxworld

    voxworld Member

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    Hi Jeff, thanks for the input.
    Turned out to be a bad solder connection on the 2nd preamp socket. Hopefully it's up and running forever now.
    Thanks for all the replies.
     

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