Datasheet for the 2SC3939 transistor in a 51.2 KB PDF, catalogued as a schematic; the _E ending likely marks an English-language release, though the name does not confirm it. Under JIS rules, 2SC identifies NPN bipolar devices. The document is the place to check pinout, breakdown ratings, collector current and package drawing when a part tests faulty or a substitute must be chosen. Match the C3939 marking and the package style on the PCB before fitting 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.