Dead spot

[Staccatomusic@cs.com]

I have an older Knabe grand with a dead spot in the mid treble section. I 
think it might have to do with the crack in the sound board. Over half an 
octave. Sound like it has a set of soft domestic hammers. no tone period. The 
hammers are striking all 3 strings so IM not sure what to test next to see if 
this is an easy fix or if the sound board perhaps needs replacement. Can 
anyone help?
RBP