Banjo-like tone in mid-treble: soundboard?

[A440 Piano Service]

Greetings,

I worked on a piano today that sounds more like a banjo than like a piano, especially (but not only) near the upper treble break.  In trying to diagnose the root cause of it I shaped suspect hammers, needled hammers, steamed them (mellowed the attack but still sounded like it had a head cold) switched hammers with neighbors, leveled and seated strings, and even replaced the action with another identical action that I had in my garage which had better hammers.

It's an 1894 Kimball upright, with vertical ribs.  No real sign of rib separation, but there are some soundboard cracks.  I took my rocker-type downbearing guage and determined that at some points, especially, but not only, near the upper break (the bridge is complete and NOT notched there, btw) there seems to be really zero downbearing.  At other points, there is about .008" clearance between the rocker end and the string.  

Humidity in the room was 28-31% while I was there.  Customer runs a humidifier in the room at night for 1.5 hours each night for his guitar.  The humidifier is about 15 feet away.

Is that 107 year-old soundboard just a goner?  Would a DamppChaser help?  Any other thoughts?

Thanks for your input,

John Dorr
Helena, MT
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