As some have already found, this problem comes from the style of action design combined with the regulation of the action, especially the damper spring tension and damper timing. A tentative player (i.e., most relative beginners) will experience bobbling the most, because they do not play the key smoothly all the way to the bottom. More experienced pianists sometimes sit down at the same piano, play a quiet piece of music, and have no problem. I've done this in the past, and it added to the frustration of the piano owner to have me play it and say hmmm, seems OK to me . . . . Bad move on my part. The best diagnostic test is to have the pianist play something that causes bobbling and watch if the damper pedal is in use. It will almost always occur when the damper pedal is _not_ in use, meaning the fingers are being stopped by the damper springs in combination with the jack springs. If you then ask the player to mash the damper pedal down and hold it, then play the same music, you should find that the bobbling has stopped. If it still occurs, recheck regulation and friction. The solution in almost all cases, once you have confirmed that the standard regulation points are good (letoff, blow, key height and dip, capstans, backchecks), is to look at the damper timing and move it away from the jack contact with the letoff button. Damper timing should be at 1/2 of the hammer blow, which should be early enough to make sure that damper lift comes sufficiently before the jack contact. In some cases damper lift can be made slightly earlier to help prevent bobbling, but this does make the touch feel heavier when the pedal is not being used. When damper lift is correct, the players fingers will naturally overcome the damper spring tension well before letoff occurs, and the finger will play the key through the full stroke. Of course, many pianos are built with too much damper spring tension. This can be regulated, but it is best to do it with the action out of the piano, in an action cradle, titled back with the dampers facing up. I place a stack of my old key weights on the damper head at the center point, and find the pressure that balances the spring tension right at the rest point of the dampers. Spring tension increases as they are pressed back, so I find the weight that makes the treble damper start to float at the starting point. Unfortunately I do not have any specifications - some day I should really look into this, and at least create some specs for Kawai pianos, which might translate to others. But in the mean time, I take what is there and observe the tension ever 4 or 5 notes. At some point in the tenor (on Kawai I think it is at G4) the tension will get suddenly higher because the spring gauge has changed. This is the critical point, in the middle of the piano, where bobbling happens. At the very least, smoothing the transition by weakening the heavy springs in the tenor to match the light treble spring tension will be a huge improvement. If the pianist is having trouble throughout the piano, then lowering the tension by 5 grams or so, while also smoothing out any transitions, then also regulating the damper lift timing carefully, will be the end of the complaint. To adjust tension, use your grand repetition spring tool. Flex the spring down (with the action in the cradle as described above) to weaken it, disengage it and pull it above the damper levers to strengthen it. With experience you can do a decent job just using your finger to test spring tension, but double check yourself occasionally with the weights. Warning: In many pianos, weakening the spring tension will cause lots of damper noises and weak damping! So don't go overboard - weaken them only enough to smooth out irregularities, or to very slightly weaken them over all. You should plan on some follow-up damper alignment work. One reason companies make the springs so strong is because it saves time when regulating dampers! Shameful, I know, but still true. Before putting the action back in the piano, apply some Teflon (TFL-50, Slide-All, etc) to the spoons and damper lift rod. Ideally these should be polished and smooth, so look for any glue deposits to clean off first. Simply press the dampers back, and spray the Teflon from the can using the little plastic nozzle extender tube. A paint brush with liquid McLube 444 works very well also, if you like to avoid aerosols. Once the dampers are re-adjusted to work well, the timing is set carefully (do you have a forked blade type spoon bender? Essential), your bobbling should be eliminated. Another tool I demonstrate in my upright class is a clear plastic block to place between the hammers and the strings. It is cut to about 24mm x 21mm, which allows you to stop the hammer at the correct point to see the dampers wink for almost all pianos. This block is wedged against the strings, then you can play each note in the piano and use the spoon bender to set the dampers to have a nice even wiggle on every note when the hammer hits the clear block. Kawai has these available for sale for something like $17 or so. Ask for a "Clear Lucite damper regulating block" when you call parts. I hope we're not sold out . . . Back to the action design. I'm not sure what the correct name is for the different action designs in uprights. I call the 2 common styles of actions American (Pratt Read?) and European (Schwander?). Asian pianos use the European style almost always. In the American design, the hammer spring is relatively strong, the jack springs are relatively weak, and the damper spring does not affect the touch very much. This is a smooth working and very reliable action design, but does not by nature repeat quite as well as the European design. In the European design, the jack springs must be strong, and the hammer springs are weak. As I've described above, the damper spring has a larger impact on the touch in this design, because the player isn't already compressing that heavy hammer spring. When working well this system repeats a little better, and many feel the tone quality is more expressive and controllable. The European design is also more sensitive to other factors, such spring tensions and also friction. Hammer center friction that is too low can contribute to bobbling at times, and if the above spring and damper regulation doesn't fix the problem, one can pick an especially bad bobbling note, pull the hammer, and see if the friction is close to zero. If so, pin it for 4 grams friction or so (measured at the flange screw hole) and try it again. If that fixes the problem, you have the solution. In doing some testing in recent months, I have confirmed that these actions really need their strong jack tension. It is tempting to try weaker jack springs to stop bobbling, but the repetition will really be bad, especially in slow to medium-speed repeition, like in a trill. In a related issue, insufficient aftertouch can also lead to repetition problems, because the jack spring is not being compressed enough. Upright actions rely on the jack spring to help to push the wippen (and therefore the key) down when the player lifts the finger. If the spring is weak, or if the spring has not been compressed enough, the repetition rate will be poor. Gravity alone (using the mass of the key weights at the back of the keys) is much too slow to do a good job of letting the note repeat. Wow, long epistle. I hope it is helpful to some. Don Mannino -------------- next part -------------- An HTML attachment was scrubbed... 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