A brief 48.3 KB PDF on the 2SC3504, catalogued as a schematic but containing transistor data. The JIS 2SC prefix classifies it as an NPN bipolar device of the high-frequency type. Given the small size, expect a condensed sheet with maximum ratings, main characteristics and the pin layout rather than extensive curves. That is still enough to test the part with a meter, recognise a failure and choose a replacement with equal or higher limits. Confirm the marking and package on the board before trusting the pin order.
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.