This 170 KB PDF carries the part number 2SJ502 and is indexed under schematics. In JIS naming, 2SJ marks a P-channel FET, so the document is expected to be the datasheet for that transistor, not a board diagram. Read it to obtain maximum drain-source voltage, drain current, gate threshold and on-resistance figures plus the pin layout, which together guide out-of-circuit testing and selection of a compatible substitute. The name lists no maker or package, so check the case style before replacing anything.
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.