Today I'm happy again, I solved it!
As askhlut pointed out (thank you!), it was the D6 diode. I went to an electronic store and they sold me a generic diode that works for 24-35V. I desoldered the burned one, soldered the new diode and voila, it seems everything works perfectly so, if anyone connect by error the DC cables with the incorrect polarities it will surely burn the D6 diode, in fact, I guess it is designed to protect the rest of the board, of course, burning itself but cutting the connection between the power supply and the Rumba board; and so, the solution is to remove the burned one and solder a new one (it only cost 5 cent of euro).
=)
As askhlut pointed out (thank you!), it was the D6 diode. I went to an electronic store and they sold me a generic diode that works for 24-35V. I desoldered the burned one, soldered the new diode and voila, it seems everything works perfectly so, if anyone connect by error the DC cables with the incorrect polarities it will surely burn the D6 diode, in fact, I guess it is designed to protect the rest of the board, of course, burning itself but cutting the connection between the power supply and the Rumba board; and so, the solution is to remove the burned one and solder a new one (it only cost 5 cent of euro).
=)