Document for the 2SK1806 in PDF format, 136 KB, catalogued as a schematic. The 2SK code marks an N-channel FET under JIS naming, so the contents are likely a component datasheet. Look for the ratings table, characteristic curves and outline drawing showing which pin is gate, drain and source. This information supports diode-mode testing of a suspect device and helps choose a substitute with sufficient voltage, current and power handling. Check the package on the PCB first, since the name does not state it.
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.