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Hammond M-100 percussion issue

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  • Hammond M-100 percussion issue


    my M-100 percussion is behaving like a normal drawbar.
    If I switch it on (with no drawbar pulled out), the tone is lasting as if I had pulled the related drawbar out.
    It is the same for both percussion types and it does not change for fast or slow percussion.

    There is no change when I adjust the percussion cutoff trim at the amp.

    Terminal K is behaving normally, so pulled from approx. 25V to Ground when a key is depressed.

    I also had a look at the bottom of my amp (A0-67). All wires seem to be ok.
    I also swapped the tubes with no difference in result.

    There is one small ceramic capacitor (I think on the socket of tube 7 - the second one from the right) that seems to be a bit worn out. (edit - I think it is C28 - is that relevant for this issue?)
    Does s.o. know the value for that? I could not read it.
    And I only have a very bad picture...
    Click image for larger version

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    C31 seems to be ok from the visual inspection only. I have not desoldered it by now to measure it.
    Would this be a candidate for this issue?
    Is there a way to measure this one in curcuit?

    Any help appreciated.

    Greets, Mark
    Last edited by markimark; 09-16-2018, 06:34 AM.