Beginning Tech: Upright Reg. - Hammer Blocking

[Newton Hunt]

Hi, David,
      A more likely effect is that the backcheck is forcing the hammer
against the string because the dip is too deep and cannot be detected because
the backcheck is too close to the backstop.
      Move the backcheck back enough to provide full clearance, check the
dip with a block of known demension, adjust as needed then re-regulate the
backchecks.
      It IS possible that the jack is binding against the let-off rail or
liberty rail (if it has one).  Check by depressing a key fully and push down
on the toe of the jack to see if there is any free movement.  If none, check
the dip, as above, then move the let-off rail away from the jack just a
little.
      While you are at it, check to see that there is some slack in the
bridle straps.  If there is too little the butt can pull the backcheck to the
backstop.  If you step on the soft pedal and observe the backchecks moving
then the straps are regulated too tightly.  The spec is that the strap
becomes just taught when the pedal fully depressed or the hammers are no more
than half way to the strings.
      If these do not solve the problem let me know.
            Newton
            nhunt@gandalf.rutgers.edu