CP contamination on Yamaha S 400-B

[Erwinpiano]

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   Mark

  I've seen this problem for years. It first showing up in years1976&77. =
The plated center pins flake off in the bushing cloth and voila,mass =
friction Yamaha was very good about paying for this type ofe warranty =
repair so I'm guessin it was fairly wide spread.

.     Tis a good idea to use a roughend reamer to remove crud,Then =
polish and  reinstall a real brass center pin.  I've done massive =
amounts of this kind of repinning, largely in the hammer flange(wippen) =
but have done several complete damper tray assemblys as well. Once there =
goin bad I repin everything.  If its under warranty guess who I'd be =
calling?

    Best Dale Erwin



  ----- Original Message -----=20
  From: Mark Dierauf=20
  To: pianotech=20
  Sent: Friday, May 04, 2001 5:06 AM
  Subject: CP contamination on Yamaha S 400-B


    I had a customer complain about the touch on their Yamaha grand and =
discovered that it weighted off at 66 grams at middle C. When I checked =
the hammer flange I found that I could only get one swing, and that the =
bushings had a black residue on them. Closer inspection showed that this =
residue was also on the center pins as well as slightly in the wood =
surrounding the bushings. The residue on the pins themselves rubbed =
right off, and the pins looked shiny and new without any signs of =
buildup or corrosion. I repinned one to normal tolerances and the cloth =
felt as if it had normal resiliency, and the downweight dropped by 11 =
grams. I also found that the wippen flanges had the same residue, but =
hadn't seized up the way the the hammer flanges had. They seemed to be =
*slightly* on the tight side but still within normal tolerances (I =
didn't have my little spring gage with me). The jack & rep lever =
bushings were normal bright red cloth, and perfectly free.
    I have an appointment to return and repin this action, but before I =
do I wondered if anyone else has run across this before. Could this be =
something that Yamaha did at the factory? although I've certainly never =
seen it in their other grands, this is the first S series grand that =
I've serviced. The customer bought it used last year and so doesn't know =
it's history. Does anyone know of any center pin lubricants that react =
in this way? Is the problem likely to return after repinning? The serial =
# is: U3894763
  =20
  Thanks,=20
  Mark Dierauf

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