Yamaha bobbling

[Richard Brekne]

That about sums up the two basic general case causes

For a piano in proper regulation, bobbling must either be caused by 
improper geometry (your situation 1 is one example of this) or something 
impeding that last bit of key / whippen / jack travel . (your situation 
2 is one example of this)

As Ron Nossaman mentioned, a light player not playing through correctly 
is also something we see a lot of.  So anything that contributes to an 
hindrence to that last bit of key stroke is going to show up as big time 
bobbling for those kind of players.

I dont really buy the jack acceleration reasoning. You gotta figure 
Yamaha has enough engineering savy to design the action well enough to 
avoid that kind of a mistake. And besides, I personally have never had a 
problem solving a bobbling problem on Yamahas... or most any other well 
made piano.

Cheers
RicB

Jorgensen, Michael L wrote:

>     I have seen two additional causes of bobbling hammers in our 50+ Yamaha U1 and P22 uprights.
>
>1.  In one case the screws which hold the blocks of wood which support the action bracket feet had become loose.  The action had shifted in slightly such that the capstans were farther from the wippen centers.  This  results in less action travel for a given keydip.  After comparing other P22s I made about a 1/16" shift of the base of the action toward the player, which corrected the problem. 
>
>2.  One case had bobbling hammers only with the damper pedal down, and took me a long time to make them bobble myself but a pianist had complained.   The wing nut which regulates damper pedal travel had loosened so that there was slight damper movement when the pedal was already down.  A very light player would simply stop pushing the key further down when the damper spoons contacted the levers, so the jacks didn't fully clear.
>
>These are wonderful pianos for their size, and are holding up beautifully after seven years.  
>
>-Mike Jorgensen   
>
>
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