Good old Technics forum!!!!
My great keyboard lost it's voice,everything loaded and appeared to work ok but no sound!. Having an idea this had happened before
to a forum member,so checking the past posts success!!!.
Mike Daniell in Australia had the exact same symptoms back in 2009.The fault was traced to IC643, the negative 15volt regulator on the FAJ board. Mike quoted a generic part as LM7915
but be carefull as Panasonic use a high spec for the component.
Panisonic use a KIA7915PI (TO220) made Korea Electronics.
Good new this is still made and here in the UK. W D Greenhills have them on the shelf. These are the High spec items,you might get away fitting a generic but it's life may be shorter and if it goes down it may take other items as well
costing a lot more in the long run.
Regards to all John.
P.S. Part has now been changed, and the KN7000 is singing with
full force once again.