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

[Mark Dierauf]

I don't see many U3's, but I know that on the U1's the keybeds seem to
move around a lot, causing excessive lost motion in the dry season
that's just ending here in New England. If this is the case in your
situation then be prepared to crank those capstans back down once things
moisten up substantially. A Dampp-Chaser will generally take care of
this problem, though.

- Mark

-----Original Message-----
From: John M. Formsma [mailto:john@formsmapiano.com] 
Sent: Monday, April 12, 2004 10:27 PM
To: Pianotech
Subject: RE: "Bobbling" hammers on a new Yamaha U3. ( Please help! )

Gordon,

Did you check for lost motion first?

I'd guess that regulation will correct everything unless there is actual
damage to the butt leather. If some hammers are bobbling, that's
generally an indication of the blow distance being too great. Or the
capstans are not high enough (too much lost motion).

Also, checking should be closer than 1 inch, which will also help
correct the bobbling. Check the capstan height (aka lost motion) first,
though, as this will have an effect of checking distance.

I sure would look at everything else before filing the jack top. That
would be the least likely on my list. Not saying it ain't so, but Yamaha
has made millions of those things and it would seem we'd have heard
about from them if there were a problem.

John Formsma



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