[pianotech] jack test / "winking" hammer

[Richard Brekne]

Yamaha precepts new knuckles for this test. And they say so at both the 
Academy, Little Red School House, and the Aftertouch classes they give 
around the globe. If the knuckles are worn, this test is less then 
acceptable.  That said... if you have worn knuckles... you should 
replace them :)

Good point about the rep lever spring tension and centers. Leads nicely 
to the overall picture that the jack needs to be able to slip back under 
the knuckle. For that to happen correctly all parts need to be in good 
shape, and nicely regulated.  If you have badly worn parts and must work 
with them... then regulating fudge is your only path.

Cheers
RicB


    Yamaha does this test strictly with finger across the rep top.   Run
    your finger along a piece of paper lying on a surface.  That is the
    feel you are looking for.  Yamaha doesn't think it is that important
    in the scheme of things.  If it feels lower than that and looks like
    it, you may have too low rep tension.   Check the pinning on a rep
    lever.  Some are advocating 6 grams friction.   If you've got 0 or
    little, try repinning and re-regulate the rep tension for hammer
    rise.   That will give you more power in the jack return.  Don't tap
    the jack lever, hold between two fingers and move it back and
    forth.  What you really want is to feel some friction there with a
    little hammer movement.   Key is the same friction feel from one to
    the other.  You also need to be looking from the side with the
    neighbor hammer up out of the way.  The jack needs to return under
    the knuckle.  You wink the jack and watch for return.  If the jack
    doesn't return, the rep lever is too low.   You let go of the jack
    for the return.

    David Ilvedson, RPT
    Pacifica, CA 94044