String buzz

[Jeff Tanner]

Hi all,
I ran into a problem yesterday I've never seen before.  The piano: Yamaha,
I'm guessing P2 (I don't think it's a P202, but I don't see a model
number).  When the damper pedal is pressed, E20 buzzes on the C#29 damper
lever (2nd into the bass section) on a fortissimo blow.  My temporary
remedy was to bend the damper stop rail towards the damper levers in that
section and reduce pedal lift by adjusting the pedal to the point the
buzzing stopped.  But there's a lot of pedal movement now before the pedal
rod contacts the damper levers, and not much lift at the bottom.  So, the
pedal feels "squishy" now.

Here's the "pre-temporary-remedy scenario":
Part of the damper lift problem is in the pedal lift, with the treble
dampers lifting gradually ahead of the bass, so that it takes more pedal to
lift the bass dampers.  Still it's not a lot of difference, and I'm
thinking that even with even damper lift, you're gonna get the buzz still.
The damper lever felt shows no sign of wear, either from the rod or the
spoon, which I find amazing for a 30 year old piano.  Spoons are contacting
the damper levers perhaps a little early in the travel, but I don't see the
relationship there at first glance.  But even with early spoon contact, the
pedal lift exceeds spoon lift.  Damper lift is too good to start over with
a complete wire bending, spoon adjusting regulation.  The only real problem
with the damper lift is the slight gradual delay from treble to bass.  I
can pull the damper lift rods and bend the hinges to even the damper lift,
replace the felts around the pedal to reduce pedal travel, but I'm not sure
that will cure the buzz.

Here's the fun part.  The owner told me that the buzz goes away during the
winter, which tells me there must be a lot of movement in the bridge due to
seasonal changes.  (My Dampp-Chaser hygrometer measured 64% RH yesterday)
He said it hadn't always done it, but has been doing it for a while now.
Maybe he'd just not noticed it in the piano's early days.  Somebody has
told him he's got a cracked soundboard and this was producing the buzz, but
I didn't see any visible cracks - at least not below keybed level -- and
that's not what's causing the buzz anyway.  This one damper/string buzz is
the only one doing it.  This damper moves exactly the same distance as its
neighbors, and I don't see that the string level on E20 is any different
than its neighbors.

I recommended a Dampp-Chaser system, but he kind of balked at the idea of
the complete system when I told him what it costs.  The back side system is
a little pricey for a piano he said he paid $900 for new.  He might go for
a dehumidifier partial system, which might make enough difference in
soundboard movement to eliminate the problem.  But I still don't understand
why it is only this one damper lever/string combination which is doing it,
when I see no visible differences between it and its neighbors.

Any ideas?

Thanks for listening, and sorry it took me so many characters to lay out
the problem.

Jeff