Vince, I have had this problem on a few pianos. One very obvious thing that I have not seen mentioned is making sure there is enough after-touch (key dip). That being so obvious is probably why it has not been mentenioned. One other thing is the height and angle of the backchecks in relation to the hammer tail. Although this is probably not DIRECTLY related to bubbling hammers, it might help to improve the checking if these things are not correct as is. All the other things that I know of that might help have already been mentioned. Hope this might put you on another line of thought, if you haven't already solved the problem. Avery Todd University of Houston atodd@uh.edu
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