I have a alesis iO Dock 2 , and the power plug in broke and i lost the little piece but it was working ok, so im trying to plug ( solder) the charger direct to the pcb but it does not say which one is positive or negative anybody can help me? Or is there a tutorial about finding the positive and negative on a pcb board whit no electricity runing?

In advance thanks.

⟐ Answer edited May 16, 2019 at 8:14 MST