Bill, I'd use an electronic keyboard hooked through an amplifier if necessary. Most of them have some sort of pitch adjustment. Dale Dale Probst Assistant Institute Director PTG Annual Convention Kansas City--July 21-25,1999 wardprobst@cst.net (940)691-3682 voice (940) 691-6843 fax http://www.ptg.org/1999/conv/ -----Original Message----- From: owner-pianotech@ptg.org [mailto:owner-pianotech@ptg.org]On Behalf Of Bill Ballard Sent: Sunday, July 11, 1999 9:46 PM To: pianotech@ptg.org Subject: Vibrator as Diagnostic I'd been listening to a grunting sound, like a fallboard-to-front-stretcher or loose metal lyre brace, during the tuning of a Falcone 74, sympathetic to F4. In trying to chase it down, the best I could come up with was that it was coming from inside the action cavity (loud and clear). So I fastened anything inside I thought could be making noise: damper upstop rail, damper assy mounts, action brackets to key frame, the rails on the key frame. At first it seemed to go away when I pried downward on the action brackets from the pinblock. The key frame bedding was quite solid. I could not follow the sound over the strings, or under the keybed. But for all this screw-tightening, I never had direct access to the sound, because it required the action being in place to play F4 (348 Hz). What I needed was a signal generator, tunable to any pitch in the hearing range which could drive a speaker magnet to inject 348 Hz onto various spots inside the action cavity. It would sure excite the sympathetic vibration. Has anybody ever done this? Would a Dremel tool on a rheostat do this? (My first thought was a vibrator, but I would have no idea whether they are tunable or not). Bill Ballard, RPT New Hampshire Chapter, PTG "If we see you SMOKING we will assume that you are on fire and will take appropriate measures".......Sign in a Music Dept. Hallway
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