Reference PDF for the 2SC5420 transistor, 69.2 KB, indexed as a schematic though the bare part number points to a component datasheet. Japanese JIS naming assigns the 2SC prefix to NPN transistors, most often high-frequency parts. Use the document to locate the emitter, base and collector pins, read marking codes on SMD packages, and check that a substitute meets the original ratings. Nothing else, such as revision or manufacturer, is given in the file name, so verify the marking on the actual component.
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.