- On the video, it is very clear that 'the jack of the wippen' the upright piano (F2) is not functioning. 'The wippen' itself is clearly offset to 'the jack' right. Its 'the jack' has detached from the wippen there. Why can we assume this?
The reason is that when the (E2) hammer strikes the strings at the beginning of the video, we can see that it is functioning properly, whereas 'the jack' (F2) and its corresponding hammer do not work at all, even with strong pressure on the corresponding key there. Moreover, we can clearly see that while attempting unsuccessfully to make 'the jack' (F2) work here, its 'the backcheck' almost tries to catch 'the backcheck' of the (F#2) because it is offset to the right. 'The jack' (F2) is dead there.
Most likely, the repair option of fixing the detached 'the jack' from 'the wippen' will be required using glue there (3) . When 'the jack flange' has detached from 'the wippen', you'll need to remove the action from the piano and unscrew 'the wippen' from the action. Then, use PVA glue to reattach 'the jack flange' into the groove of 'the wippen'. Alternatively, there is a low possibility that 'the screw of the wippen flange' is not tightened. Need tighten it's.
Here are ALL possible solutions to the issue of the hammer not striking the strings.
If the upright piano hammer isn't striking the strings, it may not be due to 'the capstan of the key' being too low, as the entire 'the wippen' would need to be low along with 'the jack' too there. But we don't see it there. ALL possible solutions it here too:
1 'The jack flange' is broken.
2 'The pin'/ 'the screw' securing 'the jack' to 'the wippen' has come loose or fallen out.
3 'The jack flange' has detached from 'the wippen'.
4 'The jack spring' has come loose, is damaged, or lost. 'The jack spring' should push 'the jack' forward to the hammer there.
How to Fix It:
1 If 'the pin'/ 'the screw' securing 'the jack' to 'the wippen' has come loose or fallen out, you can attempt to reinsert 'the pin' into 'the jack flange's hole using a screwdriver.
2 If 'the jack spring' has come loose, is damaged, or lost, gently pull the spring upwards to increase its tension. If it's whole damaged, replace it with a new one.
3 If 'the jack flange' has detached from' the wippen', you'll need to remove the action from the upright piano and unscrew 'the wippen' from the action. Then, use PVA glue to reattach 'the jack flange' into 'the groove of the wippen'. (similar to how we see it doesn't work on video and need try fix it's so).
4 You have the option to either glue the broken flange 'the jack flange' or replace it with a new one.
https://youtu.be/rmTwms8hkDs?si=QYx3IjRKblXcPcWM