I love working with Yamaha pianos; however, Yamaha uprights made before approximately 1988 suffer a common problem. These pianos make use of a particular kind of flange (called with a Schwander-style or Japanese flange), which in its earlier incarnations relied of a thin piece of cotton thread. That thread, used to retain the hammer return spring, will break over time.
The newer design uses synthetic thread and theoretically will last the lifetime of the piano. You can distinguish easily between the two styles: The original cotton threads are brown, and the newer synthetics are white. Some aftermarket replacements are green, and these are also agreeable.
One repair I now do routinely is a Yamaha “Flangectomy”— the total replacement of every one of the original, old-style flanges with the new style. These are some pictures of the process.
The replacement flanges purchased through piano supply houses (such as Schaff Piano Supply) generally come with #19 center pins. If you have the sort of console pictured here where the center pins go through the hammer butt (as opposed to the kind with a metal plate and a screw), the #19 will not fit. I’ve heard technicians say they sometimes fit, but I’ve never once seen a Yamaha console—and I’ve now worked with dozens of these—that required anything less than a #20.5 pin, and usually a #21. I used #21.5 pins here.
The pin should be absolutely tight inside the hammer butt, such that there is no chance of lateral motion or even rotation. An adequately sized center pin is very important. Pins as small as #19 fit so loosely you can actually hear them knocking when you strike a key firmly, and if they’re even somewhat loose they can slip out over time.
Conversely, the pin should rotate relatively freely inside the flanges. There are several tests for this, but the one I use is pretty simple:
1. If you pull the flange all the way forward on the hammer, it should freely swing back and tap the hammer butt with a definite click.
2. If you straighten the hammer shank with the flange (simulating the hammer being pressed against the strings), the hammer should swing back easily under the pressure of the spring.
However, the pin shouldn’t be loose either. The hammer should be constrained such that it won’t be able to move side-to-side even when played firmly.
Practice reaming the flanges of throw-aways before you start working on a whole set.
A final note on positioning: It’s of the utmost importance the hammers are lined up precisely with the strings, and traveled correctly. Traveling can be largely done on the workbench. From time to time, it’s necessary to swap out one of the new flanges with a different new flange, as that might be more reasonable than trying to accommodate an imperfect new flange.
And my costumer loved this set!