troubleshoot a problem with my privia px-100

[Jeff in Brooklyn]

I have a Casio Privia PX-100. I've lost velocity control on C# above C2, up chromatically to the G# above that. So eight notes total. I.e, they are loud as hell regardless of how gently I strike them.

I've opened it up and vacuumed out a bunch of hair and dust. I haven't cleaned the contacts with anything, but they look ok to my eye. My guess is that it's a bad board.

I've uploaded a file

 

[Wes]

Likely a problem with one "combination" in the scanning matrix in my (very limited) experience. Check the traces, make sure none are cracked, make sure no detrius has managed to short one trace to another or to ground. Also check the associated diodes on the back of that board.

FWIW, my money is that you will find a shared trace for those keys going back to a select line on the MPU, and that trace will have a physical defect for the keygroup you've identified. Remember, too, that since your keyboard is velocity-sensitive that there are two sets of traces for each key group.

Some theory: http://highlyliquid.com/hl2012/blog/52

Wes