weedeewee wrote on 2024-02-12, 20:44:

Whomever started with the suggestion of replacing the fuse with a 47 ohm resistor should check up on his knowledge of ohms law.
Especially given the idea of a 100mA current draw (which seems appropriate for a keyboard).

Please calculate the voltage drop that causes.

I have to admit that I was underestimating the voltage drop and was counting only current.

I've made an experiment, putting 47 Ohm in place of the 0 Ohm resistor that was in place of F1/R1 and got the following:
keyboard does work, responds to keypresses, but the incoming 2.8 V is actually insufficient for LED drivers, which are supposedly resistors.

However, speaking of replacing so-called fuses with different parts, I can report this.
These are the variants of parts staying in series with the keyboard Vcc: which I've found on my MB collection
1. Surge protection pattern on PCB (1/4 of boards)
2. Actual fuse (3W, one-two boards)
3. 0 Ohm 1/4W carbon film resistor (1/3 of boards)
4. Choke/ferrite bead (1/3 of boards)
5. Nothing (direct PCB track, few boards)

So, finally, thanks for pointing to my mistake, will edit the initial comment.