A 291 KB PDF dedicated to the 2SK1830. The 2SK code is the Japanese JIS designation for N-channel field-effect transistors, so this is almost certainly a datasheet, filed here as a schematic. Its larger size suggests characteristic graphs alongside the ratings table and package drawing. Use it to verify pin assignment, gate threshold and maximum drain-source voltage when testing or replacing the device. Any substitute part should equal or exceed these values and share the same package as the footprint on the board.
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.