Dave made a few good points for replacement of the back action. Another is to replace the older version without the brass set screw bushing because the wood is fragile and will not hold the screw tightly or simply cracks. One could install these inserts but another reason is to replace the old stiff sostenuto tabs with the spring-loaded tab version. I also take the opportunity to move the tray pivot to be in line with the flange centers. This is accomplished by holding the end block and a flange to the rail and tapping the pin with a hammer to dimple the block. This makes the pedal lift the same motion as the key lift and there is no discrepancy with setting the upstop rail. I also set the pivot height such that the key lifts the underlever to a position parallel to the key bed. A pivot which is too high has the underlever at too steep of an angle and digs into the lifter felt causing drag and wearing a trench (which Dave mentioned). Reducing the lifting friction makes the action play more smoothly. Lifting beyond parallel is counter productive too. Lifting to parallel induces the least friction. Sometimes you can not change the back action as it happened recently on an 1884 Chickering grand. The wood was deteriorated enough not to hold the threaded wires securely, so I installed the brass inserts. Fortunately there was no sos. to contend with. -- Regards, Jon Page
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