Brief PDF, about 30.2 KB, for the 2SK2509, a JIS-designated N-channel FET as indicated by its 2SK prefix. The lowercase file name gives only the part number, with no maker or package details. Small sheets like this usually summarise pinout, ratings and the package drawing. When a power or audio stage fails, the document helps identify which pins to test, what voltage the device withstands and which equivalents meet the requirement. Verify the marking on the board component first.
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.