The 2SK1900 transistor is the subject of this 99.3 KB PDF, catalogued with schematics. Under the JIS convention, 2SK designates an N-channel field-effect transistor, so the content should be a datasheet rather than a circuit diagram. Use it to verify lead assignment, voltage and current ceilings and thermal limits before testing the part in circuit or fitting an equivalent. The name does not state the maker or package, so match the code printed on the component against the document 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.