Here is the schematic diagram of the Commodore 1571 floppy disk drive. The schematic also applies to the built-in 1571 in the Commodore 128D to some extent, but not to the 1571CR, which is integrated on the motherboard of the Commodore 128DCR. You can find those diagrams among the Commodore 128 schematics.
Mirror sites – General information – File types – Data transfer