At 316 KB this 2SK2145 document is larger than most in the set, so it may hold extra characteristic curves or several package variants. It is labelled a schematic, but the bare part-number name suggests a datasheet. In Japanese JIS designations 2SK identifies an N-channel FET, and the name says nothing about the maker. Open it in any PDF reader to check ratings, pin order and package drawings. Compare the device marking on the board before ordering or substituting.
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.