Part number 2SC3955 is all the name reveals for this 40.7 KB PDF, filed among schematics yet most probably a transistor datasheet. Under JIS, the 2SC designation means an NPN bipolar transistor. Expect maximum ratings, gain figures and a mechanical drawing, the details needed to confirm pinout and choose a replacement that will tolerate the same voltage and current. Japanese parts are commonly marked C3955 on the body, so check that code and the package type on the board.
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.