I was so focused on the IC not to think about searching for the board, another good suggestion!
I already had got another HP printer to look for the IC or the board, but before taking it apart I tried substituting the diode which caused the fault (I soldered another SMD Schottky, since I'm sure it was into a simple buck converter). Unexpectedly, it worked.
Perhaps it won't be reliable, for two reasons: because of the cooked IC and because I also substituted a cap with a smaller one, since by mistake I removed the original in a bad (disrupting

) way, due to lack of the proper tools.
A quite strange thing is that on the board another cap was emitting some audible noise, something it was "frying", but it was OK.
I opened the thread here because of the description of the section says "if you want to talk about or ask questions for a specific product then do so here". However, it's a good suggestion, if one needs more replies.
Problem solved, however, thanks.