First off I don't have access to a schematic.
Secondly, if she overloaded/reversed the power circuit chances are that nothing is salvageable on the board except for the mechanical components.
Could be blown voltage regulators, could be blown caps, could be some sort of hidden fusible link or the CPU itself could have been fried.
Authorized service center would just swop out the main board and be done with it. IF they still had the part.
Honestly this one is not worth the money to fix.
CDP-130 is at least ten years old and one of the lowest end pianos that Casio produced. It sold for about $500 new.
On the used market a working model is worth maybe $150 to $250 depending on condition.
Blown to hell it's literally worthless.
Seriously it's not even worth that much for spare parts.
Tell the poor woman it's time to buy a new keyboard.
Gary
