81 JMP 2204 conversion to EL34

Discussion in 'The Workbench' started by stickyfinger, Feb 23, 2021.

  1. stickyfinger

    stickyfinger Well-Known Member

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    I want to convert my 81 2204 to El34. Still has what is probably original 6550 GE tubes.
    I don't know what the correct resistor values to use. With the 6550 the plate voltage is 380- 395 (I forget!)

    Grid leaks will be NOS 220k Piher. But what Piher value do I need to use for the bias feed resistor and trim resistor? I cant find any board shots of European 2204s with el34s.

    I'm guessing 220k feed and a 56k or 47k trim. I'm pulling the board to do it proper and don't want to do it twice!
     
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  2. StingRay85

    StingRay85 Well-Known Member

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    81 2204.jpg

    '81 2204 with EL34
     
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  3. stickyfinger

    stickyfinger Well-Known Member

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