action reg puzzler on M & H BB

[Mark Potter]

ed440 at mindspring.com wrote:      Mark-
  See if the jack is just a little slow to return when it has been held in extreme let-off position for a moment.
  No, it is fine.
   
  See if the hammer cushion on the wippen is low.
  It is true that these rest felts are individual ones, rather than a rest rail, so there is SOME slight differences from note to note, but well within tolerances  - ranging from 1/2 the thickness of the shank to perhaps as much as the full thickness.  Interestingly, these three notes span that range (all slightly different, but within the 1/2 - 1 range.
   
  Thanks for the suggestions, though, Ed.
  Mark  


  -----Original Message----- 
From: Mark Potter 
Sent: Sep 25, 2006 12:08 PM 
To: Pianotech List 

Subject: action reg puzzler on M & H BB 

  List -
   
  I am having a puzzling problem with a M & H BB grand action that I have never encountered.  Complete regulation (w/new shanks& hammers), everything works great with the exception of 3 notes - F6, A#6, G7 -  in the high treble.  I cannot get this to happen on the bench, and even in the piano when the notes are played softly, even in a trill, they perform perfectly.  However, under continuous mf - ff blows, as in tuning, after anywhere from 1 to 10 strikes (letting the key all the way up), the hammer will get caught on it's way back up by the back check, thereby not allowing it to strike.
   
  I have tried numerous adjustments to the angle of the back check as well as to the height of check for these 3 notes, to no avail.  Everything seems to be identical to the surrounding notes, including jack reg - both in the window and to the knuckle core -, rep spring strength, key dip, stroke, the arc of the tails, let-off, drop, etc., etc... you name it.  Keys are rebushed and moving freely.
   
  If anyone can shed some light on this puzzler I would be most grateful!!
   
  Mark Potter  

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