Instability puzzler

[Will Wickham]

Mike,

Take a close look at the brace. I've seen a baldwin studio and an  
Everett studio that developed a crack about half way down. In both  
cases the crack was discovered because of tuning instability.

will wickham


On Dec 6, 2007, at 10:09 PM, Alan Barnard wrote:

> Since it is at the break, see if you have separations in the bridge  
> laminations or the bridge from the soundboard. Is there any change  
> in tone on the notes that go flat? A lot of the Hamilton studios get  
> this problem right at that break: It can get so bad that the notes  
> have a sound to them like a drummers wood block being struck with  
> the drumstick. Anyhow, movement in the bridge could/would in theory  
> affect pitch.
>
> Alan Barnard
> Salem, MO
>
> Original message
> From: "Michael Kurta"
> To: Pianotech
> Received: 12/6/2007 8:43:50 PM
> Subject: Instability puzzler
>
>     Yamaha MX100 w/Disklavier (U1) 6 years old, in a H.S. vocal  
> music room, never moved from there.  Climate controlled year around.  
> At the tenor/treble break the F#5 and G5 go out of tune overnight!   
> We've had trouble with this piano since new being unstable, but its  
> getting much worse now.  Lovely instrument, sounds great when tuned,  
> but almost immediately goes flat around this brace.  Measured all  
> the notes today after having pitch raised and tuned 9 days ago.  SAT  
> says all notes within 2-3 cents except those mentioned and a few  
> others here and there up to 15 cents flat.  Measured these again  
> after finishing up today, and they're 5 cents flat within 45 min.
>     Strings look good, bridge, pins and hitch look fine, pins are  
> tight and smooth, no plate separation from back, running out of ideas.
>     We called the dealer who will in turn bring Yamaha in now.  Any  
> thoughts?
>     Mike Kurta
>     Syracuse chapter

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