bias tube guitaramplifier

Discussion in 'General Electronics Chat' started by Thomas.R, Oct 14, 2008.

  1. Thomas.R

    Thread Starter Member

    Aug 16, 2007
    20
    0
    hallo,

    a friend of me asked me to bias his tube guitar amplifier. after some research on the net i found out that the circuit is a fixed bias circuit.
    so by regulating the negative grid voltage i can regulate the anode current.
    now for knowing the max dissipation you have the formula, P= anode current*anode voltage
    i can measure the anode voltage but to know the anode current, i placed a resistor from cathode to ground and measured voltage across this resistor.
    by applying ohms law i can approximately calculate the current.

    now my question; can i leave the resistor of 1k at the cathode?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    No.
    If you left it in, when the tube started conducting, the resistor on the cathode would act as the load.
     
  3. Andrew Leigh

    Well-Known Member

    Sep 8, 2008
    92
    2
  4. legac

    Well-Known Member

    May 4, 2005
    54
    0
    Voltage dropped through one (1) ohm resistor or (2.2 ohm) can be measured to adjust bias voltage. Higher value of resistor will tolerate the working point of the tube.
     
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