Hammers that stay stuck

It would seem to depend on the center pins. Check the pins: capstan, escapement lever, hammer capstan. Then inspect the spoon that lifts the damper. Almost always, due to wear or poor quality felt, a "hole" forms in the felt that causes the spoon to get stuck. I don't see any impediments in the key lever. Let me know

Over the weekend I dedicated some time, and I limited myself only to attempting to bring it back into tune. With the utmost care and caution so as not to stress the strings (it took me almost 4 hours, always in very tiny steps), as it was flat by more than a 1/4 tone, and since quite a bit of time had passed since the last tuning. In the end, I noticed that some hammers that previously exhibited the problem described in the first post have changed their behavior. Those related to F and F# remained the most critical, while some that showed this defect lightly have worsened; for one or two I noticed an imperceptible improvement; others (2 or 3 in the treble) that did not sporadically exhibit this malfunction are no longer returning to position.

I can't wait to check the hammer action as you advised me to see better where they are getting stuck. I felt it was necessary to report this strange behavior, but perhaps it is something normal and predictable. I should add that for the moment I have absolutely neither touched nor removed the action; I only acted by rotating the tuning pins (following the tips in the video guides).

pianoexpert wrote:

It would seem to depend on the center pins. Check the pins: action center pin, escapement lever, hammer cap assembly. Then inspect the spoon that lifts the damper. Almost always, due to wear or poor quality felt, a "dent" forms in the felt that causes the spoon to get stuck. I don't see any impediments in the key lever. Let me know

As you anticipated, almost all the spoons of the defective keys suffer from the problem you described. After dismantling the action, delicately touching the felt with my finger, I tried to "flatten" the dent and indeed the hammer benefited from this operation because it can now return to position (though I don't know how long it will last). This is thanks to the fact that the spring of all the dampers works very well, and therefore they are able to push the hammers back into position. However, if I block the dampers, the difference between healthy hammers and less healthy ones is immediately noticeable, as some of them (those that originally get stuck) cannot return to position without the help of the damper action (the others, however, do so without problems). This makes me think that the pins might not be in perfect condition either.

At this point, however, I stopped, because while I was able to perform the previous actions without dismantling anything delicate, I believe it is necessary to remove the defective hammers to check the pins. From how you described it, since there is a combined action of 3 pins in the movement, I haven't been able to understand which of the 3 causes the problem or if they are all compromised to varying degrees.

But yes, you can do it. You need to unhook the strap. Check the hammer like this.. Then hold the key steady and let only the capstan pivot. Then, with one finger, move the escapement lever and see if it returns easily on its own, even when the hammer is in the resting position. You will easily identify the state of the pins, which you can also verify by separately disassembling the hammer and the capstan. Replacing the pins is an expert task, and I advise you to rely on a good technician.