The 2SK1839 is covered in this 84.9 KB PDF, filed under schematics though the name points to a single semiconductor part. In JIS nomenclature 2SK denotes an N-channel FET. Expect the usual datasheet sections: maximum ratings, characteristics curves and the outline with pin numbering. Use it to identify gate, drain and source on the actual board before testing, and to find an equivalent if the original is unavailable. Always match ratings and the package footprint, and cross-check the body marking against the number.
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.