Buzz problem

[Dave Nereson]

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  ----- Original Message -----=20
  From: Maxpiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: Wednesday, June 27, 2001 9:15 PM
  Subject: Buzz problem


  I ran into a problem today that I could not correct despite an hour of =
trying=20
  before tuning the piano.  I was stymied despite my nearly 50 years'=20
  experience tuning pianos.  Has anyone on the list experienced the same =
and=20
  found the answer?

  The piano:  a Baldwin Howard spinet, S/N 1,095,157 (1976).  A rattling =
buzz=20
  with hollow, false tone in the first octave or so of the bass =
indicated a=20
  loose bass bridge.  Not so.  Bridge was tight to the shelf, the shelf =
tight=20
  to the sound board.  Yet pressure against the bridge would restore the =
tone=20
  just as with a loose bridge.  Seating strings made no change.

  Pulled the piano out from the wall.  No junk lying there, no loose =
ribs, no=20
  separation of the sound board from the liner.  I scraped the sound=20
  board-to-liner joint for loose glue.  I got a bit but there was no =
change in=20
  the tone.  I checked the sound board button screws, all except one =
were=20
  tight.  Anchored that one and still no change.

  I noted one curious fact:  from the front, I could stop the buzz by =
pressing=20
  elsewhere, such as on the tenor bridge above the "loose" area and on =
the=20
  board in the same area.  Checked the area between plate and board with =
a=20
  flexible steel, but found nothing.  Checked with a mirror to see if =
the plate=20
  was coming loose bottom, but its "nubs" were right up against the =
board.

  >From the back, with the customer banging low C, I was able again to =
silence=20
  the buzz by pressing in the general area of the bass bridge.  Then I =
became=20
  aware that there was a scraping, grating sound as I pressed in on the =
board,=20
  and again as I released it.  (I recall a similar experience with a new =

  Baldwin grand in the early '70's; I never did hear how the dealer =
handled=20
  it.)  There is a hole in the sound board (plate bolt) in this area, =
but there=20
  is plenty of clearance with the bolt. =20

  The board gives the impression of solid spruce, but the joints visible =
in the=20
  front do not correspond with the joints visible from the rear. Am I =
dealing=20
  with a laminated board and could it be delaminating?  If so, what can =
be done=20
  about it?  The cutouts around plate bolts show no separation, yet the =
area=20
  around the plate bolt between bass and tenor bridges is the area where =

  pressure silences the buzz.

  Since I am on a trip, the customer is over 100 miles from my home and =
I will=20
  be passing by their home on my way back in two days (Friday), I would=20
  appreciate any input from the group.

  Bill Maxim, RPT
  Columbia, SC

      Where a nose bolt passes through the soundboard, look at the edge =
of the wood with a bright light to see if there are layers (laminated).  =
How to tell if it's delaminating, I don't know.
      Do the bridges rub against the plate or a plate strut anywhere?
              --Dave Nereson, RPT

  =20


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