Filed under schematics, the 143 KB PDF named 2SJ509 most probably holds the datasheet for a single transistor, since 2SJ in the Japanese JIS scheme designates a P-channel FET. No application, brand or package is given by the name. For bench work, the sheet supplies pin assignments, maximum ratings and electrical characteristics that let you test the part out of circuit, judge whether it has failed, and choose an equivalent with similar voltage, current and on-resistance. Confirm the marking on the real 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.