Does anyone have any service manuals/schematics/etc forr NEC fd1055 (or fd1050/1053) 5.25" floppy drives?

I've got one that's giving a disk fault 18 - which I think is not reading a sector so could be anything from alignment upwards; but occasionally gives a drive fault 10 (index sensor??)

But then again it could be the beeb it's attached to; so hmm suggestions welcome.

#retrocomputing