Champ nasty distortion

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by echidna, Mar 5, 2015.

  1. echidna

    echidna Member

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    Just made made a Champ and first test it has a nasty distortion which sounds typically like bad O/T. Changed the tubes and no change in bad sound. Could it be anything else or could it be a bad brand new O/T?
     
  2. pdf64

    pdf64 Member

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    It's possible but human error in the build seems more likely.
    Perhaps you've (unintentionally) made an oscillator?
    What schematic / layout have you used?
     
  3. echidna

    echidna Member

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    Thanks. I'll comb through it and see if i made any mistakes.
     
  4. Dan40

    Dan40 Supporting Member

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    Could be a wiring mistake like pdf64 mentioned or possibly a bad solder joint. Did you check the current draw on your power tube after the initial start up?
     
  5. echidna

    echidna Member

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    I just did a quick voltage check and everything is scary high. The MT is 320-0-320
    and some readings are

    5Y3 Pin 2: 475v
    6V6 Pin 3: 473v Pin 4: 445V
    12AX7 Pin 1: 244

    Filter Caps
    1: 472v
    2: 443v
    3: 382v

    So what could be making those voltages be so high and what can i do?
     
  6. telenut62

    telenut62 Member

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    Check you have the filter caps and the 220K resistor linked to ground.
     
  7. echidna

    echidna Member

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    Just checked them and they are grounded.
     
  8. telenut62

    telenut62 Member

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    Faulty rectifier?
     
  9. mark norwine

    mark norwine Member

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    Your voltages are so high, you're producing awfully asymmetrical output.....which, indeed, sounds dreadful.

    While I can't say for sure, I suspect you "constructed" it correctly, but there's more to building an amp than just soldering in the components.
     
  10. pdf64

    pdf64 Member

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    What's the voltage at terminals 5 and 8 of the 6V6 (control grid and cathode)?
     

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