Named solely for the 2SK2777, this 425 KB PDF is catalogued as a schematic but most likely contains the component datasheet. JIS nomenclature reserves 2SK for N-channel FETs. Technicians consult such a sheet to confirm package and pin order, read breakdown voltage, current and power limits, and compare characteristics with a cross-reference part. Nothing else is stated in the name, so verify the marking and footprint on the board, and also look for the root cause that destroyed the original transistor.
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.