Hi Folks,
If I am correct the internal memory of the KN650 is retained by the use of a Lithium battery which was supposed to last about 5 years from purchase at which point you were supposed to return to your "Technics" dealer to have a replacement fitted. Now this might be a problem, as if it is the same in the US, as it is in the UK. Dealers are charging a fortune and or trying to talk you into a new keyboard.
If you know a good engineer try getting a quote, and do your sums as to the best option for you, perhaps moving up a model with disk drive may be a good investment for you.
Best regards John.