Yamaha YUS3 Regulation

That it is out of regulation is no doubt. The fact that you cannot depress the keys easily may depend on various "friction resistances". If you feel the need for more aftertouch (with this refined term you might have impressed the seller!!!😀), it means that the keyboard has little depth and the hammer stroke will not be completed (perhaps it will also tend to strike back against the string because the escapement lever cannot complete the escapement under the cap tooth). But didn't you try it in the shop?

Anyway, send me a video. Perhaps after this general intuition, I can understand better.

P.S. It could be that the seller does not have a competent technician... it happens! So call an expert technician at your own expense... it might be that only a fine-tuning is necessary. If instead there are permanent impediments, then have them put it in writing and, if necessary, ask to replace the instrument.

summarizing: New piano, everything was fine in the shop.

1) the piano is a different one.

2) the action shifted (not properly secured) during transport, or even worse, it took a significant hit.

Sometimes, I would dare say often, sellers make the keyboard easier so that it may appear more docile; or, as is common practice, they do not resolve any friction at its source, but instead adopt a lubricated palliative. The problems become apparent later...

Perhaps with a shallower dip in the shop and a generous lubrication (the effect of which lasts a couple of days if the friction problems haven't been resolved at the root), they made it so that the keyboard seemed incredibly smooth to you!!! At home, however, you obviously felt poor aftertouch.

Some technicians insisted on setting my dip to 9.5 mm because Steinway does it that way and the keyboard is more responsive. Reasoning devoid of all logic. Every action has its own geometry and there exists a formula to determine the MINIMUM dip: this means that even Steinway's 9.5 can be brought to something slightly more.

To understand what the geometry of the action is, one only needs to think of a lever: by changing the position of the fulcrum, lowering one side, the other side rises n times; the closer we bring the fulcrum, the more advantageous this relationship becomes, but with more inertia. The same thing happens with the piano action, obviously considering the interaction between the different levers. A geometry with a 1:4.5 ratio (10mm dip, hammer-to-string distance 45 mm) is different from one with a 1:5 ratio (9.5 mm dip, hammer-to-string distance 47 mm, Steinway).

On average, modern actions require a dip of 10/10.3 mm. If this measurement is reduced, you get bobbling (you would feel the hammer bouncing on a light stroke) and playing pianissimo can become a terrible experience (absurdly, by nullifying the aftertouch, the hammer does not escape). In the presence of conical repetitions (excellent!), the aftertouch measurement must be generous because, by not compressing on the fortissimo, the energy would return to the pianist.

Congratulations Francesco, you have hit the nail on the head and well-argued "the scenario"!!!! Anyway, in Fabio's case, too many things don't add up and the instrument should be examined closely, reconsidering all adjustments, not least the correct position of the action rail, which may have been forced. In short, I insist: an excellent technician must be called to London to perform a good regulation of the instrument and identify the problems that Fabio is experiencing. These could be minor issues, but they produce significant inconveniences.

As far as the correct aftertouch is concerned, there should not be, as Francesco rightly says, a rigid rule. Some pianists prefer more aftertouch, others would like a minimum. All mechanical adjustments can be customized....naturally within certain limits.