We had a similar problem with a Hamburg D. Protek CLP seemed to make it better for an hour or two, then it became worse! Sizing, or fitting the balance rail holes also worked temporarily, but fast repetitions of any key made the squeak sing again, until it "cooled off" (for lack of a better term). Imagine having multiple complaints about "squeaks" on a premier concert instrument and when you come to the piano it's not there! Finally we tried fast reps., and voila, the squeak appeared. We then cleaned the balance rail hole with one or two light insertions of a sleeve of fine sandpaper (you're just cleaning, not removing wood) which came out slightly blackened. No more problems after nearly 3 months. It appears that "CLP" (Cleaner-Lubricant-Protectant) may have cleaned the pins because they didn't show residue when polished, but dirt, etc. seems to collect in the wood at the balance rail hole. Up until now I've used CLP on balance rail bushings without hestitation, but if the balance rail hole is not properly sized AND cleaned it may aggravate other problems. Jim Busby RPT
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