Yamaha bobbling

[Jorgensen, Michael L]

     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