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Adjusting bias on BDRI (missing TP?)

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  • Adjusting bias on BDRI (missing TP?)

    Okay, I sort of hijacked the other thread, so I'll start a new one..
    Here's original post...

    Newby, here, and new owner of a Blues Deluxe. I'm very interested in this thread because I'll probably be experiencing similar problems (although I love the sound of this amp!) I downloaded the service manual from the above link so that I can replace the output tubes and adjust the bias when needed (I can't leave anything alone). I cannot find TP47 on any of the schematics to check the voltage. I've traced from the pot (R82) and still cannot find TP47.
    Any help greatly appreciated.

    Add: Is TP26 possibly the same as TP47? It's in section 10 with the R82 pot.
    Thanks.

  • #2
    It appears to be a typo. The indicated TP26 is indeed the test point for measuring/setting the bias.

    It is a 1 ohm resistor hanging off the cathode to ground. It is a voltage measurement that equates to the idle bias current. E=IxR and since R is equal to 1, that voltage is equal to the current multiplied by one.

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    • #3
      Makes sense. Thanks for the response.

      Comment

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