Filed as a schematic, this 59.7 KB PDF is titled 2SC5128 and presumably holds the datasheet of that NPN bipolar transistor. Japanese JIS numbering reserves 2SC for NPN parts originally classed as high-frequency. Only the part number appears in the name. Use the sheet to look up collector-emitter breakdown, current limits, gain ranges and package dimensions while testing junctions or picking an equivalent. Because close part numbers can differ greatly in ratings, confirm the exact number printed on the failed device.
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.