This is a good quality scan of the service manual which includes an assembly diagram, block diagram, schematic, and parts list. Exactly what is needed to repair my KR-V55R receiver.
Text excerpt from page 19 (click to view)
SECTION 4 MECHANISM DECK ASSEMBLY
Note: Follow the assembly procedure in the numerical order given.
OPTICAL PICK-UP COMPLETE ASS�Y
1 Move the lever (LOCK 3A) in the direction of the arrow A, and return it a little in the direction of the arrow B from the position where the chuck plate is moved down to the lower limit.