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Thread: add bias pot to 1988 Carvin X100B EL34

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    add bias pot to 1988 Carvin X100B EL34

    I have a 1988 Carvin X100B with original EL34s. I want to replace them with different models of EL34s to get a different sort of tone. I want to ensure the bias is correct but this particular model/year doesn't have a bias pot. Does anyone have the steps to install one? I can solder pretty cleanly but don't know the specific steps. I have biased an amp before ( but it has a bias pot).

    Thanks in advance.

    Sam

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    Supporting Member Jazz P Bass's Avatar
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    Here is Carvins link for the schematic.
    Link:http://www.carvinservice.com/crg/sch...0Schematic.pdf
    The specifically state "select R127 for idle current of 100ma".
    I guess you could put a 100K pot in place of R127.
    Solder the wiper to one of the outside legs or the pot.

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    add x100b bias pot

    thank you. I've seen that schematic before; The work doesn't sound to complicated as long as you do neat work. Amp's with a tech right now, if he can't do it, I'll give it a shot.


    Thanks again.

    Sam

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    Old Timer Gtr_tech's Avatar
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    None of the x-amps had a bias adjust pot. I've added them to all of mine.

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    The farmer takes a wife, the barber takes a pole....

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    add x100b bias pot

    thanks fellas;

    GTR_Tech since you've done this before, is there anything specific I need to watch out for? Also, do you have a recommendation as to tolerance and wattage?

    Sam

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