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

[Jeannie Grassi]

I guess I never quite understand why technicians hesitate to call the
factory representative associated with respective companies.  Yamaha has
one of the best technical support teams around. Is this coming from the
same logic as people not wanting to stop to ask for directions when they
get lost?   

Do yourself and the client a favor...call Yamaha, they're very friendly
folks...and approach it professionally.

jeannie

Jeannie Grassi, RPT
Associate Editor, Piano Technicians Journal
mailto:jcgrassi@earthlink.net


-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Mike Bratcher
Sent: Tuesday, April 13, 2004 5:55 AM
To: Pianotech
Subject: Re: "Bobbling" hammers on a new Yamaha U3. ( Please help! )


I had this exact problem with several of our newer P22's at a local
university.  My partner and I pondered over this.  We did full
regulation
with no help to the problem.  We eventually decreased blow distance.
This
worked.  And yes we checked lost motion, let off....etc.  We fooled with
compromising all regulation aspects and felt blow distance was the best
compromise.  We never contacted Yamaha although the amount of time we
put
into it we should have been compensated.

Mike Bratcher

----- Original Message ----- 
From: "gordon stelter" <lclgcnp@yahoo.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Monday, April 12, 2004 5:17 PM
Subject: "Bobbling" hammers on a new Yamaha U3. ( Please help! )


> Ladies and Gentlemen of the List,
>      I maintain a Yamaha U3 for a church here, which
> is only one year old, yet has developed "bobbling"
> hammers on about 25 notes. The immediate cause is that
> the front edge of the jacks are not all escaping from
> under the butt buckskin on letoff, althouigh the
> keydip is "at specs", and the letoff is much more
> generous than "spec": varying from 5 to 10 mm!
>     My first effort at correcting this problem will be
> to meticulously regulate this piano to Yamaha factory
> specs, although I believe that this will only make the
> "bobbling" worse. I believe that this will occur, as
> the strange, current "regulation" on this little used
> instrument ( besides the aforementioned "letoff"
> distances, the hammers are checking at an inch or more
> from the strings ) seems to have been effected to
> overcome some inherent design flaw ( or flaws ) which
> does not allow the jacks to readily slip out from
> under the hammer butts.
>    The percieved design flaw to which I refer is a
> very sharp edge on the plastic jacks' front edge,
> which seems to catch on the buckskin, causing the butt
> to bounce upon it repeatedly rather than allowing the
> jack to fully slip out.  This problem  may also be
> exacerbated by the use of an overly "nappy" buckskin,
> and an unusually sharp angle on the hammer butt
> buckskin face, at the point where where the jack would
> normally "trip out".
>     It seems that a tiny bevel, were it filed on the
> front edge of the jacks, would be efficacious in
> remedying this "bobbling". I may also try sanding down
> the butt buckskin and lubricatinmg with some microfine
> Teflon.
>      My first efforts, however ( after regulating the
> action ) will be to reduce the hammerstroke, and
> perhaps increase the keydip by 1 mm.
>      If you please: Have any of you encountered a
> similar problem on a piano of this model and, if so,
> how did you approach its remedy?
>
>      Your advice will be gratefully recieved,
>      Sincerely,
>      Gordon Stelter
>
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