<html> <body> Alan - I'm sure I'm not saying anything you don't really know already.  It's the spiral of action regulation refinement.  You say <blockquote type=cite class=cite cite="">The jack height adjustment, or more correctly the repetition lever height adjustment, must be made before letoff, drop, etc</blockquote> but adjusting the rep spring will change the rep lever height ( and hammer line),  and changing the checking height will require an adjustment in the strength of the spring (maybe), and you can't really assess checking height without having some kind of let off...etc.   Small measurements are always critical, sometimes. :)  At some point, the effects of further refinement become, spiritual, philosophical, or egotistical, (or pathological) but not discernibly physical, so the process can cease. <blockquote type=cite class=cite cite="">But too little (jack too high, lever too low) takes the rep lever out of the ball game entirely as far as repetition is concerned. </blockquote> As always, I may be wrong, but it seems that your description above is actually reversed.  If the lever is too low, the jack will not easily, or at all, return under the knuckle.  In subsequent key stroke,  hammer will be propelled ONLY by rep lever, which, of course, cannot produce let off. While I am unfamiliar with the particular piano in question, I am reminded of a similar problem I had with some early Renner USA - Steinway replacement parts.  I found establishing stable hammer line almost impossible.  The process of adjusting the rep lever height seemed to go directly from being too high (slight lost motion & unstable hammer line) to too low - jacks would resist complete return.  I ultimately tracked the problem (I believe) to a discrepancy between the arc inscribed by the top of the jack and the profile of the top of the rep lever arm (cradle?)  If regulated precisely at the same height, at rest, the arc of the jack top would dip below the lever profile as soon as it's travel began, thus eliminating the tactile sensation of the jack dragging along the knuckle.  By the time one was able to accomplish the standard benchmarks...slight drag and hammer wink, the jack top was significantly above the lever, and resisted return. David Skolnik At 09:42 PM 10/30/2005 -0600, you wrote: <blockquote type=cite class=cite cite="">Phil has it (I think). The jack height adjustment, or more correctly the repetition lever height adjustment, must be made before letoff, drop, etc. Because we are dealing with something in the order of 2/10ths of a millimeter that has to be adjusted by feel, it is easy to have it wrong even if it "looks" right. I learned, in this challenging little experience, that a very, very slight change in height makes all the difference in the world. Too much of a gap creates obvious lost motion detectable by slowly pressing the key down. But too little (jack too high, lever too low) takes the rep lever out of the ball game entirely as far as repetition is concerned. Now here's a true confession: I honestly don't know why this made such a difference, but after much frustration, I rechecked this adjustment, raised the lever (lowered the jack, relatively) and was THEN able to set a letoff and drop just as sweet as you please. Prior to that, no combination worked! Key point: The adjustment on this note looked just like it's neighbors--and they regulated just fine. >>> I'd actually appreciate explanation or comment from you who have regulated so many more actions than I. As Yamaha so aptly states: "One large difference between a grand action and a vertical action is that the grand has the repetition lever. However, the lever loses its value in direct proportion to how poorly is is regulated. Remove all lost motion, but make sure the jack can return under any circumstance. Then the repetition lever can live up to its name."   So here, brand new and hot off the press, is "Alan's Maxim":  If you are having trouble regulating an action, back up a few steps and make sure you have good regulation in those earlier steps.   Might save ya some tears some day!  ;-} Alan Barnard Still Larn'n, Thank'e, in Salem, MO > [Original Message] > From: Phil Bondi <phil@philbondi.com> > To: Pianotech <pianotech@ptg.org> > Date: 10/30/2005 6:44:10 PM > Subject: Re: Puzzler for a rainy Sunday afternoon ... > > Spring tension non-existent? > Jack too high in the window? > > ..this is a good puzzler, > > -Phil Bondi(Fl) > > _______________________________________________ > pianotech list info: <a href="https://www.moypiano.com/resources/#archives" eudora="autourl"> https://www.moypiano.com/resources/#archives</a></blockquote></body> </html>