Why does the (F3) key on an upright piano produce a short sound when pressed?

[maxim_tuner]

• https://youtube.com/shorts/cdp3SWx-Dxc? ... vklnrvwMLO
  Introduction:
  In a video, it was observed that when pressing the keys F#3 and G3 on an upright piano, the sound is sustained. However, when the F3 key is pressed, the sound is very short. Additionally, it was noticed that 'the head of the damper block' for the F3 key rises significantly less compared to the F# and G keys. This technical issue can be resolved by following the steps outlined below.
  How to fix it yourself:
  1 Ensure no foreign objects are obstructing 'the damper lever'.
  2 Make sure there are no foreign objects underneath 'the damper lever', which could affect its movement.
  3 Verify the correct positioning of 'the damper spring' for the F3 key.
  4 Check that 'the damper spring' for the F3 key is correctly placed on 'the damper lever', similar to the neighboring keys. If 'the damper spring' has shifted, carefully use tweezers to return it to its standard position on 'the damper lever'. Test the kinematic condition of 'the damper block' by pressing the F3 key and observe its movement. Adequate lighting can aid in this inspection. If the issue persists, consider removing the piano action from the upright piano. If none of the previous steps resolve the problem, it may be necessary to remove the piano action for further examination and repair.
  Alternative method: Adjusting the damper wire using a hollow tube. If removing the action from the upright piano seems daunting, an alternative approach involves using a metal or plastic hollow tube (at least 10 cm long) with a slightly larger internal diameter than 'the damper wire'. The tube should fit onto 'the damper wire' with a slight backlash, allowing for slight bending in the direction away from the F3 strings. Follow these steps to adjust 'the damper wire':
  1 Remove 'the damper block' from 'the damper wire' by unscrewing 'the damper block screw' with a screwdriver.
  2 Place the tube on 'the damper wire' and gently bend it towards you. Once 'the damper wire' is bent, reattach 'the damper block' onto 'the damper wire', ensuring it aligns with the other 'the damper blocks' and does not touch adjacent ones during movement.
  Additional issue: 'The Damper spoon' misalignment. If 'the damper block' functions similarly to the video, where 'the damper spoon' has shifted, follow these steps:
  1 Carefully detach the action unit from the upright piano for better access to 'the damper mechanism'.
  2 Check the interaction between 'the whippen' and 'the damper spoon'. Press down on 'the whippen' (F3) with your finger and observe if 'the damper spoon' catches 'the damper lever'.
  3 Compare the differences between the neighboring damper spoons. To fix the issue, gently push on 'the damper spoon' and lightly bend it towards the front, closer to 'the damper lever'. Conclusion: By following the outlined steps, you can address the issue of the F3 key producing a short sound on an upright piano. Remember to exercise caution when working with the upright piano and consider seeking professional assistance if needed.