A 126 KB PDF dedicated to the 2SC5257, sorted into the schematic section although the name identifies a single component. In the Japanese JIS system, 2SC designates an NPN bipolar transistor; nothing about package or ratings is given in the name. Use the document to confirm collector, base and emitter positions and to read the electrical limits before replacing a suspected faulty device. Check that the code printed on the original part matches, then pick a substitute with equal or better specifications.
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.