Mysterious unsolvable Yamaha double-striking uprights

[David Ilvedson]

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A couple of things...the jack isn't cycling out from under the=
 butt.  You can solve this by shimming the hammer rail slightly=
 and taking up the lost motion and or increasing dip slightly. =
 Before doing this check blow distance and dip and see if=
 something is out of whack.  

David Ilvedson







Original message
From: Geoff Sykes 
To: "Pianotech@Ptg. Org" 
Received: Mon, 11 Jul 2005 23:04:27 -0700
Subject: Mysterious unsolvable Yamaha double-striking uprights


Greetings --
 
I did a dealer prep on a brand new, fresh out-of-the-box, Yamaha=
 MX500 P upright today. Every single note double-struck when=
 played softly. I checked regulation and had to adjust lost=
 motion on every key. Let-off also needed to be adjusted, but=
 only on about 10 keys. When I finished these two adjustments the=
 regulation may not have been perfect but it was certainly close=
 enough. Still, every single note was double striking when played=
 softly. (Definition of "softly": Playing the note faster then=
 when you are checking let-off but slower than it takes to=
 actually check.)
 
What I am witnessing is this: When I play the note, just before=
 the jack releases from under the butt the hammer jumps off the=
 jack prematurely and strikes the string. After striking the=
 string the hammer then bounces back onto the jack, which is=
 still in it's pre-release position. Continuing through the=
 keystroke results in the hammer striking the note a second time=
 as the jack finally releases from under the butt. 
 
This was something new to the store manager so I called an=
 associate. He suggested I go through the routine I had just=
 completed, but otherwise could offer no further suggestion. OK,=
 so I decided to tune the thing while I pondered the matter=
 further. 
 
Aha! Tuning finished. Let's see what the other Yamaha uprights=
 are doing. I checked six other, (not used), Yamaha uprights on=
 the floor, (none of which I had prepped, but all of them=
 allegedly prepped), and every single one of them exhibited the=
 same double-strike behavior. For comparison I then checked some=
 NON Yamaha uprights and they all behaved properly. I finally=
 checked the showroom Yamaha action model, and it, too, was=
 behaving correctly. BUT... It was then that I noticed that all=
 the Yamahas used in this test had plastic jacks. The Yamaha=
 action model, as well as the non-Yamaha uprights used in this=
 test, all had wooden jacks. 
 
That's all the clues I have. Anybody have any idea what's going=
 on, and what can be done to correct it?
 
Geoff Sykes
Assoc. Los Angeles Chapter


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