Hammers won't check on D

[MR ROLAND KAPLAN]

Thanks to Ed Foote for one of those "I might not have figured that
out for years suggestions."

Here is another diabolical plot.

If hammers are worn they are light.  If hammers are too light they do
not counterbalance keys effectively when they return.  Customer
complains of poor repetition, blocking (hammer trapped low in
backcheck, jack stuck in front of knuckle).  Enterprising tech enter
scene and increases tension on repetition springs.  Presto, poor
checking, bobbling hammers that hit a second time, and the repetition
is still lousy.

Do the hammers need replacement?
   Roland Kaplan