"Bobbling" hammers on a new Yamaha U3. ( Please help! )

[Dave Nereson]

----- Original Message ----- 
From: "gordon stelter" <lclgcnp@yahoo.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Monday, April 12, 2004 4:17 PM
Subject: "Bobbling" hammers on a new Yamaha U3. ( Please help! )


 > the front edge of the jacks are not all escaping from
> under the butt buckskin on letoff,

    Either 1) let-off occurs too late in keystroke, or 2) there's not enough
dip, or 3) blow distance is too great, or a combination of these three.

>>althouigh the
> keydip is "at specs", and the letoff is much more
> generous than "spec": varying from 5 to 10 mm!

    That's a major part of the problem.  Let-off should be 1/8 inch or less
(about 3 mm).  If the jack lets off earlier in the keystroke, then it's got
all the rest of the key travel to come away from the butt before the key
hits the front rail punching.  That may be your only problem!  But read on.

>     My first effort at correcting this problem will be
> to meticulously regulate this piano to Yamaha factory
> specs,

    Yes; and decrease the blow distance a little if you have to.  Make sure
lost motion is minimal to non-existent.  But the jacks have to get back
under every time.  Depress the damper pedal, press keys down in groups, or
"handfuls", then let them up very slowly and see if all the jacks return all
the way under the butts.  If not, introduce a tiny bit of lost motion until
they do.

although I believe that this will only make the
> "bobbling" worse.

    I doubt it.

>>the hammers are checking at an inch or more
> from the strings )

    Should be 5/8"  (16 mm).

 >     It seems that a tiny bevel, were it filed on the
> front edge of the jacks, would be efficacious in
> remedying this "bobbling".

    I would call Yamaha tech. support services first (1-800-854-1569, Bill
Brandom) before attempting this, since it's new and still under warranty.
If you file those jacks without consulting them, you may void the warranty.
If you do file them, make sure it's the tiniest bit.  If you round them off
too much, they may then "cheat" or skip out from under the butts on a hard
blow, before let-off occurs.  You don't wanna have to replace all the jacks
or wippens!!

>>I may also try sanding down
> the butt buckskin and lubricatinmg with some microfine
> Teflon.

    That wouldn't hurt, but just sand enough to remove excess fuzz, and
again, remember it's still under warranty.  I imagine the excess fuzz or
roughness will wear off normally with use.  Again, call Yamaha first before
you go altering too much stuff on a new piano.
    As someone else said, this isn't the first one of these they've made,
and it shouldn't require alteration of parts to get it to regulate properly.

>      My first efforts, however ( after regulating the
> action ) will be to reduce the hammerstroke, and
> perhaps increase the keydip by 1 mm.

    That's a good plan, but regulate that let-off closer first!

>      If you please: Have any of you encountered a
> similar problem on a piano of this model

    Occasionally, but it was always remediable by regulating properly.

      Your advice will be gratefully recieved,  [That's 'receive'.  i before
e except after c or in words where the 'ei' sounds like ay, as in "neighbor"
and "aweigh".

        --David Nereson, RPT