Reference PDF for the 2SK1457, filed under schematics and 122 KB in size. The file name carries only the part number. The 2SK designation follows the JIS scheme for N-channel FETs, so the contents are probably a component data sheet rather than a board diagram. A repair technician would read it for gate threshold, drain-source voltage, maximum current and pin assignment when testing or replacing the transistor. Compare the body marking and package outline on the PCB with the drawing before choosing a replacement.
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.