NEC ND3520A

interesting question.
But one must ask this question actually more in general:
Where are to get Service Manuals and schematics from pc stuff like motherboards, accessories, cd and DVD burner, HDD and SSD devices.
This I want to know.
For consumer Audio and Video products you will find all schematics there:
Schaltpläne und Bedienungsanleitungen: SDL Digitaler Buchdruck
Unfortunately Schemas of PC parts here are not available.