A 423 KB PDF referencing the 2SK2311, with no details in the name beyond the part number. The 2SK prefix is the JIS code for an N-channel FET, so the document is presumably the datasheet despite the schematic label. Use it to read pinout, breakdown voltage, drain current, threshold and capacitance values, and to compare candidate replacements. Any PDF reader opens it. Before relying on the data, confirm that the device body marking and case type match what the sheet describes.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.