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<DIV><FONT face=Arial size=2>Is the heat/AC blowing directly on the =
piano? From
which direction? Have you sat a thermometer on the belly area and =
observed any
temp swings during one (or more) of these pitch-drift =
cycles?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I would say that if the pitch cycles as =
the
temperature cycles, then that is likely the cause. You would need to =
stabilize
temp.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I once tuned a Yamy grand for an =
outside concert.
The sun/clouds was playing peek-a-boo on the soundboard/strings. Pitch =
would
rise and fall wildly 10 cents or more! Sounds like your situation might =
be the
same thing - only from a vent.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Terry Farrell</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=mark@nhpianos.com href="mailto:mark@nhpianos.com">Mark =
Dierauf</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, June 16, 2004 =
10:26
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Unstable Yamaha =
C7</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face="Times New Roman" color=navy =
size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: navy">I take care of an older Yamaha =
at a
recording studio that has a tuning instability problem that I’ve =
never
encountered on any other piano – the pitch fluctuates by as much as =
3 or 4
cents over the course of only a few minutes. It took me quite a while =
to
realize that this fluctuation ran in sync with the forced hot air =
heating
system. Now that it’s summer, the air-conditioning from the same =
vents is
having the same effect. The piano has a complete DC unit installed =
with a
bottom cover, is tuned at least 20x annually, and is very pitch-stable =
in the
long term. It is not located in direct sunlight and the temperature =
doesn’t
vary much, certainly not within seasons. In the winter there is a =
humidity
control system adding moisture through the hot air ducts. The studio =
is in an
old </SPAN></FONT><st1:place><FONT color=navy><SPAN style="COLOR: =
navy">New
England</SPAN></FONT></st1:place><FONT color=navy><SPAN =
style="COLOR: navy">
barn that had several hundred thousand dollars worth of renovation, =
and so is
very well finished and insulated, but in the time that it takes me to =
work
through the temperament the first notes tuned have already moved
substantially. Once after chasing the pitch all through a tuning I =
repeated A4
for several minutes and watched the pitch rise about 2 cents above the =
starting point then fall about 2 cents below. This cycle kept =
repeating as I
watched. Has anyone ever seen such a problem? Did you find any
solutions?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: =
Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">-
Mark<o:p></o:p></SPAN></FONT></P></DIV></BLOCKQUOTE></BODY></HTML>