Reference PDF for the 2SK2122, about 35 KB and catalogued under schematics, although the plain part-number name implies a datasheet. The JIS designation 2SK means an N-channel FET. Neither the maker nor the package is stated. A technician would use it to check drain-source breakdown voltage, current rating and on-resistance before replacement, and to identify the pins so the device can be tested for a short or an open junction.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)