[pianotech] Bobbling hammers and jack spring pressure?

[Jeff Deutschle]

Reducing the check distance and/or needling the backcheck felt may help too.

On Wed, Jan 21, 2009 at 11:49 AM, Paul McCloud <pmc033 at earthlink.net> wrote:

>  Hi, Gregor:
>     Check the damper spring tension also.  Too much tension will produce
> the same symptoms.  I found this while trying to diagnose a similar problem
> with a Chinese upright piano we were selling.
>     On another American brand, their new Schwander (loop type) action had
> bobbling problems.  I had to increase the letoff distance a bit to reduce
> the problem.  I figured that the return springs were too "weak" and soft
> play would not be hampered if I did that.  It seems that some pianos are
> prone to this even when new.
>     Paul McCloud
>     San Diego
>
>
>
> ----- Original Message -----
> *From:* Gregor _ <karlkaputt at hotmail.com>
> *To: *pianotech at ptg.org
> *Sent:* 01/21/2009 8:23:17 AM
> *Subject:* [pianotech] Bobbling hammers and jack spring pressure?
>
> 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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>


-- 
Regards,
Jeff Deutschle

Please address replies to the List. Do not E-mail me privately. Thank You.
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