Documentation for the 2SK1431, a part whose 2SK prefix places it among N-channel FETs under Japanese JIS numbering. The file is a 104 KB PDF filed under schematics, but it most likely holds the device datasheet. The name gives no package, maker or ratings. Use the sheet to look up pin order and absolute maximum values, and confirm the marking on the physical transistor matches before trusting the data when testing it out of circuit or picking a substitute.
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)