A single key on my upright piano keeps playing even after I release it. I've tried tuning the sustain pedal with the screw all the way up to the point where other keys get affected and the pedal won't sustain them anymore, but this specific key still holds the tone.

I've opened the top lid to observe the sustain hammer (I don't know the correct term for it) and it appears to push back at the strings just like the others, except it's probably not pushing strong enough because if I help it a little with my finger, it suppresses the vibrations just fine. There appears to be a screw on the end of it but it's so tight I can't turn it at all, even with the help of tools.

My understanding of the piano mechanism is limited to know where else to look to fix this problem, any advices?

  • A professional piano tuner could probably sort this out. Apr 28 '16 at 14:18
  • I thought asking here first could save me the need to call one
    – Hyperion
    Apr 28 '16 at 14:20

Usually in upright pianos there is a spring based return mechanism that forces the damper on to the string when the key is depressed. The spring may be rusty or broken in which case only replacing it will solve the problem.

Another possible cause, the axis of the damper lever may be partially displaced, giving unsuall resistance. In that case dismounting the mechanism and reinserting the axis will solve the problem. But if it's a problem with the axis, more likeley the axis felt (or nylon) bearing (not sure if that's the rigth English word for this part) is worn out and has to be replaced (easier if it is in felt, if it's nylon it has to be a manufacturer part).

It's improbable, but there may also be something causing a partial obstruction that doesn't let the damper return to its position by force of the spring alone. If the piano is very old, dust alone can be sufficient. Carefully vacuum cleaning and very gently moving the damper back and forth with your hand it's probably worth trying. You're going to have to remove the piano's front panel to properly reach the mechanism, but's usually not to difficult.

Check also if the damper felt is in good condition. Again, it's improbable, but a piece of shreded felt may be leaning against one or two of the strings, while the other(s) remain free (if it is a 2 or 3 strings note).

BTW the screw you see is probably the one that attaches the key mechanism to the mechanism frame. If that's the case and you unloose it the mechanism is going to get free and will stop working properly and interfere with the neighbouring keys.

  • Thank you for elaborate reply, I managed to solve it by uninstalling the front cover so that I could reach the screw with a screwdriver which I've set it free easily with. I've moved the faulty dampener slightly and screwed it back, which made it working properly again. I am marking this as a solution because it is most probable help someone else who might encounter the same problem as myself.
    – Hyperion
    Apr 28 '16 at 21:29

As a temporary (which may turn out to be permanent), you could stick something onto the damper, which seems like it's not pushing against the string/s enough. It will depend whether it's against 1,2 or 3 strings. Something like a small piece of foam that has sticky on one side, as long as it allows the note to play normally. It's admittedly an amateur solution, but may well work at least for now. The proper answer of course is to get the expert - a piano tuner - in, although a blind one may have slight difficulty mending this, with all due respect - they're usually brilliant!

  • Be careful not to damage the dumper further by this!
    – yo'
    Apr 28 '16 at 19:29

There are many things that could be causing this, some of which should only be repaired by a qualified piano technician. Here are some of the possible causes, along with diagnoses and solutions.

  1. Problem: The damper mechanism is rubbing against something, possibly the felt of another damper. Diagnosis: moving the damper of a neighboring key causes the faulty damper to fall back onto the string. Solution: trim a little felt from the side of the damper (DIY fine), or align the damper if it's out of alignment using the little screw on the back to loosen it from the wire, and/or by bending the wire itself (qualified technicians only).

  2. Problem: The damper mechanism isn't resting on the string, but on the lifting mechanisms of the damper pedal. Diagnosis: While looking at the dampers, gently press the damper pedal. If the dampers are beginning to move the moment your foot touches the pedal, that is bad. You should be able to move the pedal about 1/4 inch before the dampers start to lift off the strings. Solution: Find the nut that regulates the damper pedal (on an upright, it's underneath the keyboard on the rod that extends from the pedal to the wooden lever) and loosen it a couple of turns until the dampers all start lifting after the end of the pedal has moved about a quarter inch. (DIY fine) If it is just the one damper that is jumping off the string early, you'll need to get a technician to bend the damper wire to put it in line with the other dampers.

  3. Problem: Similar to 2, the damper isn't resting on the string but on the lifting mechanism attached to the key. Diagnosis: Press the problem key down very slowly and note when the damper starts to move. It should start moving about 1/3 of the way through the key's travel. (You can use the hammer travel to gauge this.) Solution, if it starts moving the moment you touch the key, you will need to find a qualified technician to bend the "damper spoon" for you. It's deep inside the action and you don't want to try to find it on your own. A reckless person could bend the spoon himself by holding the damper in place against the string with one finger, and carefully pressing the key part way down, but I don't recommend this.

  4. Problem: The damper felt is missing, or too damaged to work properly. Diagnosis: Look at it. Solution: Replace it. If it's missing, look in the bottom of the piano first, as it probably fell down there.

  5. Problem: The damper spring is broken. Diagnosis: Move the damper with your finger and feel if it wants to "spring" back to the string. Compare with other keys. Solution: Have a technician replace the damper flange for you.

If the note does NOT die away when you press the damper down manually, you could have other problems like sympathetic vibrations on a lower string whose damper isn't working, or sometimes an underbuilt damper sitting on a vibrational node of the string you're playing.

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