I know this isn't exactly Audio but It is in control of the source. This is the MCU for a diode matrix for keyscan in a Yamaha P-85 digital Piano. Multiple B and C key keys were dead. I have beyond doubt determined the missing signal to be on conductor n15 pin 23 of CN301. My problem now is that I do not know how to check for key return. I believe. I need to use my scope but I need advice.
