The manual contains detailed exploded diagrams of the transport mechanism—specifically the Tascam T-501 or a variant of the Philips CDM-9 mechanism. You will see part numbers for:

There are several ways to obtain the Tascam CD401 MKII service manual:

Note: Always use an anti-static wrist strap when probing these adjustment potentiometers (pots), as static electricity can instantly destroy the laser diode. 5. Tips for Sourcing Parts and Documentation

: Guidelines for cleaning the optical lens and lubricating mechanical parts of the CD tray. Repair & Parts Information

You can often locate and download digital copies of the repair guide on specialized audio documentation websites like HiFi Engine or ElektroTanya.