---------------------- multipart/alternative attachment Here is the text of an article I wrote for our chapter newsletter last month. It has a specific thing to look for in the Yamahas, re: double strikes. To give credit where it is due, I am fairly sure(?) the Yamaha stuff was from something Don Maninno said, wrote, or taught .... Hope it helps. Double Trouble Piano owners are usually not happy when their pianos have the "automatic staccato repetition feature," that is, bobbling (technical term: double-striking) hammers. Here are common causes and cures: Verticals Possible Causes: Inadequate key dip for the hammer stroke caused by hammer wear and/or rest felt wear/compaction; backcheck felt wear; catcher buckskin worn, damaged, or missing; checking distance too far; excess lost motion between jack and hammer butt. Other actual or contributing causes may be weak hammer springs (especially the Schwander-type butt spring), poorly shaped or worn butts (not yours, the piano’s), too little lost motion so that the hammer, at rest, is physically touching the jack (use the rest rail follow test for a quick check: There must be some lost motion); butt flange center pinning too loose. Thickness of the butt felts helps determine the jack angle as it hits the butt, which can contribute to bobbling. A rare cause is misalignment of the action or capstans in the piano, usually a manufacturing goof. Cures: Make necessary repairs. Make sure keys are level and that the backrail felt is in reasonably good shape. Regulate blow, lost motion, letoff, and checking. Check dip—make sure there is adequate aftertouch for the action to completely cycle and the hammer to check before the key bottoms out— but there must be no excessive lost motion or "slop". If the problem persists, it may help to gently hyperflex the hammer return spring to strengthen it—and make sure it moves freely in its felted slot. Sometimes removing some of the slack from the bridle strap can help. Make sure nothing is interfering with action movement, e.g., bent bridle wires. Less common, but noticed in newer Yamaha uprights, damper springs (or jack springs) may be too strong or damper spoons regulated in such a way that resistance becomes very high at the same time that the jack spring is being compressed for letoff. To check this, depress the right pedal and see if the bobbling stops. You may need to ease the spring or change spoon regulation. Grands Regulation is always the suspect, here. If the bobbling happens on a hard blow, it is likely that the hammers are not checking properly. The backchecks may need new leather and/or regulating. Worn or missing key bushings can cause the key to flop around so much that checking is affected. Evaluate the repetition lever spring and the amount of hammer drop: If the spring is too strong and/or drop is too high, bobbling may occur on soft blows. Alan Barnard Salem, Missouri ----- Original Message ----- From: Annie Grieshop To: Pianotech Sent: 11/01/2005 8:01:16 PM Subject: Yamaha jumping jacks Good evening, I had two tuning jobs yesterday that involved relatively new Yamaha verticals - an M500 and an M450. Both have very jumpy jacks (or, at least, that's my analysis of why they're tending to double-strike, even when well-regulated), and I'm wondering why. Both have plastic jacks and synthetic buckskin. The M500 had been treated with something that looked graphite-like and was less jumpy than the M450, which leads me to believe that the proper lubricant (or other treatment) might solve the problem. I would very much appreciate any suggestions as to how to proceed. Thanks! Annie Grieshop in the wilds of balmy Ioway, where winter is still in our future..... ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/f0/ba/ea/cf/attachment.htm ---------------------- multipart/alternative attachment--
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