Home GuitarPCB Forum GuitarPCB Build Support Plexi Plus bias problem (Solved)

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  • #32796
    KarelSam
    Participant

    Hello, my first post here. Plexi plus v1 on my workbench, actually I found building docs here in forum as only v2 available in PDF. Still have some issue with bias – using 50k trimpots I am not able to go lower than some 8,5v at the Drain. I do not see any changes in values of components, only changed 1N5817 diode to 1N4001 following v1 BOM. Is there something I am missing?

    Thanky ou for any help!

     

    #32798
    Barry
    Keymaster

    There is no difference other than the protection diode which has nothing to do with the circuit.

    The problem could likely be with the JFETs you are using to bias.

    What type and brand are you using?

    Where did you get them from?

    #32801
    Billy
    Moderator

    All your component values and orientation that I can see look correct

    The most likely culprit as Barry says is dodgy J201s there are a lot of fakes around

    #32817
    KarelSam
    Participant

    You were both right, I found some original Fairchild from some previous project and the problem is solved. Unfortunately only 4 pcs. The fake ones come from a local Czech dealer where I have been buying for years without problems (J201 for the first and last time).

    Many thanks !!

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