Reference PDF for the 2SC4224, at 97.3 KB, catalogued as a schematic although the name is just a semiconductor part number. In JEITA numbering, 2SC identifies an NPN bipolar transistor, so expect absolute maximum ratings, electrical characteristics and a package drawing rather than a board diagram. No manufacturer or package variant appears in the name. Use it to verify pin assignment before testing in circuit with a multimeter diode check, and compare voltage, current and gain limits 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.