The 2SD2598 transistor is covered in this 59.3 KB PDF, whose name ends in an _E suffix. Catalogued as a schematic, it is likely a datasheet, since 2SD is the Japanese JIS designation for NPN bipolar transistors in low-frequency roles. No maker or package type appears in the name. Before replacing a failed part, use the sheet to confirm pin order and electrical limits, and check that the code printed on the component body really reads 2SD2598 rather than a similar number.
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.