HP 41C DOES NOT BEEP

[aurelio]

I've checked if the BEEP could be enabled/disabled by a flag (actually I dont remember so) but it seems to be not.
This nice 41c I hold in my hands, does not beep and even "tone", just I see on the display "BEEP" when I execute the command

So strange is that this is a "serviced" calculator, I guess: the display is rounded like in the halfnut, but the calculator is a "C";by the way I've tested the calculator, writing a couple of programs and crunching a few numbers without to find (it seems up to now) any other "strange" behaviour