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Thread: Bias Adjustment on Fender Twin II

  1. #1
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    Feb 2009
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    Bias Adjustment on Fender Twin II

    I am curious as to where to read the bias current on my Twin II head and how to adjust it. The Tubes seem to run very hot even with 6l6 GC STR's.
    Thanks,
    Paul

  2. #2
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    May 2008
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    Re: Bias Adjustment on Fender Twin II

    If your amp still has the original groove tubes labled outputs, and the red labeling is all still red then they have never been run truly too hot, as when that happens the red print turns brown, also you can check for red plating by having the lights off, or covering the amp to view the outputs and look to see if on any area of the gray plate structure inside the tube you see any hint of red showing up at idle. if not then play it flat out if you can and if you still have no sign of red happening, then the tubes are not biased too hot.
    Your twin only has a bias balance adj so to ret set the bias you have a choise of two resistors that can be changed to different values, but I would get a bias rite type of tool first to see where your outputs are idling at now.

  3. #3
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    May 2008
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    616

    Re: Bias Adjustment on Fender Twin II

    your amp has no bias adj, just a bias balance adj.
    To re-set the bias you have a choise of two resistors whos value can be changed to effect the bias setting, but first I would get one of those bias rite type meters to see what current you are at now.

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