Soundboard repair question

[Fenton Murray]

   You don't fill cracks?  So, it's either replace the board or leave
    it alone?
    (That seems really sensible.)  Under what conditions do you decide to
    replace it, then?

    Annie G.

Annie,
What really matters is the sound of the piano before you tear it down. Do 
you like it, then you might want to keep the board. There could certainly be 
other things beside the SB that could degrade the tone of the piano, 
hammers, strings, terminations, bearing on the board. All that has to be 
considered. A SB not capable of holding up to a re-stringing and future 
decades of service will show it's age and fraility in different ways. Some 
of these are simply the health of the wood, think of old brown brittle 
action parts, allthough spruce, especially sitka, seems to be incredibly 
resillient, IMO. There is a mechanical design to the Soundboard, Rib, Bridge 
system which has been discussed at length here. A break down of that system, 
as in loss of crown and the ability to support the load of the strings, is a 
sign of a dead system. A string check underneath will show crown, here again 
it's only part of the story, some great sounding old Steinways out here on 
the West Coast show hardly anything under load yet sound great. Your cracks 
are just cosmetic, not that they shouldn't be repaired during a restring, I 
just wouldn't consider tearing down the piano for that one repair. And take 
the supper glue away from the professor.
Fenton