Here is a 297 KB PDF named 2SC5590, sorted under schematics but bearing only a component number, so it should be the datasheet for that part. Under JIS conventions 2SC designates an NPN bipolar transistor, commonly printed as C5590 on the package. Use the document to confirm package type and pinout, then check breakdown voltage, maximum current and dissipation against the circuit before installing a replacement, and test the junctions in diode mode when diagnosing a failure.
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.