Reference PDF, 170 KB, for the 2SD1525 transistor, listed under schematics. Japanese JIS designation 2SD identifies an NPN bipolar device meant for low-frequency work. The name gives only the part number, so the maker and package must be confirmed from the component marking. Expect ratings, electrical characteristics and dimensional drawings. Those are needed to test the part, recognise its pinout on the board and evaluate whether another transistor can replace it safely.
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.