[pianotech] Bobbling hammers and jack spring pressure?

[Carl Teplitski]

I tune many  Yamaha teaching pianos in our town, and almost all the new Yamahas
exibited similar traits described herein.   First time tuning these new pianos, I did some 
let-off adjusting.   Next time tuning , (3 months), same problem was there, although I don't
know if the same keys were at fault, cause I really didn't take note the first time, thinking
that problem should be solved. I just take a large screwdriver and bear up on the letoff rail, 
and this usually tells me that that's the problem. Other times , I've adjusted the capstans up
to make for less lost motion.  This worked, too.  Soooo, sounds like the previous writer
says that it probably needs more than one adjustment, but several.  Think he's right. 
I would like to know , if in fact,  there is a definitive answer .  ( springs ?? )

Carl / Winnipeg 
  ----- Original Message ----- 
  From: Ryan Sowers 
  To: pianotech at ptg.org 
  Sent: Thursday, January 22, 2009 5:49 PM
  Subject: Re: [pianotech] Bobbling hammers and jack spring pressure?


  My vote is for the damper springs. They are often set much stronger than they need to be and do cause some resistance to a full key stroke during gentile playing. I ran into a similar problem a while back and a compromise between a little extra let-off, a tiny bit more key-dip, a weaker damper spring, and timing just a wee bit later. Sometimes you can combine several subtle adjustments to get the result your looking for. Ultimately I believe this may be a geometry issue that these pianos might have. I was recently having a conversation with Ed McMorrow about this and he claimed it had something to do with the relations of the action centers and over centering of the hammer. We hear so much about grand action geometry but not enough about upright geometry. 


  On Wed, Jan 21, 2009 at 8:22 AM, Gregor _ <karlkaputt at hotmail.com> wrote:

    List,

    is there a way to ease the jack spring? I have problems with a Yamaha P121N upright that has bobbling hammers. The hammer butt is dancing on the jack tip. All regulation measures are okay and there is enough aftertouch. I suspect the jack spring being too strong. Any thoughts how to get it right? 

    There is no lost motion, check is about 15 mm, aftertouch is okay and I gave some talkum powder to the jack tip and the let off button. The only thing that helped was to set the let off to 10 mm, but that´s not a satisfying solution. The strange thing is that one could play without bobbling hammers but something makes the player stop pressing down the key before the let off point. A very subtile resistance gives the player a hint that the key is pressed down now, but that´s not right. The player could and should press further on. The strange thing is that this problem is new for a few days. I should mention that we had very dry air last weeks and the customer has a floor heating. Therefore I suspect a connection between this problem and the dry air.

    Any comments?

    Gregor


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  -- 
  Ryan Sowers, RPT
  Puget Sound Chapter
  Olympia, WA
  www.pianova.net
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