Unstable Yamaha C7

[Mark Dierauf]

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 I've been told by the owner that there is no change to the temp/RH
settings between uses. When I was tuning yesterday I could see that the
AC was cycling on and off frequently, so I would expect that the
temperature wouldn't vary by much. In the past I have kept a close watch
on RH levels in the winter and although it was low (mid to upper 20's)
it was steady. This is the first time that I've noticed the problem with
the AC. 
 I have certainly seen an almost immediate effect on pitch from
temperature changes caused by sunlight moving across the room and
hitting the plate and strings of a piano*, but in this case the change
was rather extreme and so not surprising. In this case, although I
haven't actually measured the temp change I can't imagine that it could
be more than a couple of degrees - less than I would have thought
capable of producing such a sudden and dramatic pitch fluctuation.
 
- Mark
 
* The other case where I saw a large pitch change caused by a sudden
temperature change was years ago when, after tuning, I tried to solve a
tight action center problem with an electric hair-dryer on a very damp
spinet piano just before a show without first removing the action from
the piano. D'OH!!!
 
-----Original Message-----
From: J Patrick Draine [mailto:draine@comcast.net] 
Sent: Thursday, June 17, 2004 7:19 AM
To: Pianotech
Subject: Re: Unstable Yamaha C7
 

On Jun 16, 2004, at 10:26 PM, Mark Dierauf wrote:
This cycle kept repeating as I watched. Has anyone ever seen such a
problem? Did you find any solutions?

The obvious solution is to control the heating and AC flow. Either the
studio should move the venting, or the position of the piano. In
addition the heat or AC should be as constant as possible (ie they don't
turn the AC on only when the tuner or player shows up).

Patrick

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