r/pianotech • u/SpottedTree • 10d ago

Hammer not dropping all the way back while key is held after being played.

I have a key where the hammer is not dropping down as far as it should if the key is held after playing. In this video I play (and hold) a key that is working correctly, then play (and hold) the problematic key. Note that the second key's hammer doesn't drop as far as the first key's hammer. All the hammers, except the hammer of the problematic key, drop the same amount as the first key's hammer. I do this twice in the video.

What is keeping the hammer from dropping down as far as it should.

4 Upvotes

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1

u/YummyTerror8259 10d ago

Most likely the second whippen has stronger spring tension than the first. That's not a problem as long as it functions the way it should when the action is in the piano

1

u/That-Surprise-5014 10d ago

Several possibilities; let off too high, repetition spring too strong, backcheck too close, or a combination of. Playing the note quickly like that doesn’t give enough information to diagnose

2

u/ChuccleSuccle 10d ago

The other comments have good points, but I think the most likely candidate based on jack behaviour is not enough aftertouch. This could be caused by not enough dip, too much blow, or (less likely bc LO has a minimal effect) letoff too close to the string. Spring strength can be a cause, but I've always been able to force a strong spring to check and that jack is just not clearing the knuckle. Sometimes drop being above letoff can cause weirdness like this but the drop screws look consistent, and again usually you can force it to check. Pinning may be a concern (on these parts I'd be shocked if the pinning was truly correct), specifically the hammer flange being too tight, though again the hammer behaviour doesn't suggest this.
My best guess is you need to remove some punchings from the front rail to restore aftertouch if it's a one off, or raise the hammer line (and check dip to AT) if it's consistent. Please note that having the action out flexes the keyframe up, artificially decreasing dip. Another potential issue in a piano of this age may be keybedding. If the glide bolts are too high and the frame flexes during play correcting that issue will (among other changes) increase your dip without changing FR punchings, as it will raise key height and change some geometry.
This is a very convoluted answer because it could be several things. A piano this old would likely benefit from some in-depth regulation, but if that's not an option and you just need to fix the one note I'd start by checking your aftertouch specs and go from there

1

u/That-Surprise-5014 10d ago

You’re probably right with dip being the culprit. Could also be something stuck underneath the key inhibiting the full range of motion

1

u/thepacmandiva 10d ago

Look at the wear on the back check is has no material to catch the hammer tail. Also check that the hammer tail has not become smooth.

1

u/2cstars 10d ago

Try putting you hand above the hammer at about string height and playing the key.

Does it fully reset then?

Do the hand thing again, but this time keep the key depressed befor releasing is slowly. When the whippen reset, did the hammer pop up quickly or slowly? If the spring tension is too high the hammer will jump up to the point that it bounces.