Yes that is the kind of connector I was referring to and it seems to me you did the right connections there.

I don't know about Sk-5 specifically but be aware that old casios are notoriously lacking any kind of protection against reverse supply polarity.
Beside not working does the keyboard show any sign of life at all?
If the power LED does not light up at all there's the possibility that the problem could still be around the power supply rails.

Hi I tried to connect the circuit straight from dc supplier with some clamps,as in photo, but is not working. I suppose I need deeper tests to check everithing is fine.

Ciao Ermangaver

thanks for you reply. The the pads are definitely out.

Taking the socket out has broken one of the pins, so I've to buy a new one. You mean this kind of connector?

Meantime, it make any sense what I designed? I used to compare the circuit with the service manual scheme below, I couldn't find any good photo of that part of circuit.

Thanks Andrea

I think so, I'd clean the area and after having figured out were the PCB traces are supposed to route the three pins, solder some wires to redo the connections.
Electrically this usually works but it will not be the strongest  in mechanical terms, looks like at least two PCB pads are gone so the connector will not be properly fixed and so it will be prone to break the connections again.
Better to change the connector with a panel mount type.
Hope this helps.

Hello, I'm completely new to circuit bending. I just found a Casio Sk5 but it have some problems on the circuit around power plug

is there anyway to bypass the damage? Thank you very much.

Andrea