Part-number document for the 2SC5173, stored as a 231 KB PDF under the schematic category. Given the naming, expect a datasheet for an NPN transistor, since 2SC is the Japanese JIS designation for high-frequency NPN bipolar devices. Nothing else, such as manufacturer or package, is stated in the name. Use it to verify the pinout before measuring in circuit, compare absolute maximum ratings with a candidate replacement, and match the SMD marking code seen on the PCB to the correct part.
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.