Please note that this is a draft paper and might not be complete or accurate. For official and complete documentation, please refer to the Korg official website or contact an authorized Korg service center.
If you are not confident in micro-soldering, use the service manual to (find exactly which board is dead), then order a replacement board and perform a simple "board swap." Swapping a joystick assembly or keybed is simple; replacing a CPU is not. Korg Pa700 Service Manual
Korg uses a rubber contact system under the 61 keys. After heavy use, the carbon pads wear out or dust gets underneath. The in the manual shows you exactly how to remove the keybed (usually 15-20 screws) and which replacement contact PCB (Part Number: KIP-1234-xxx) to order. Please note that this is a draft paper
Detailed electrical blueprints of the primary circuit board, including the CPU, RAM, and sound synthesis chips. Korg uses a rubber contact system under the 61 keys