Brief 29.4 KB PDF for the 2SD1555, held in the schematic section, though the name is just a part number and likely belongs to a datasheet. According to the Japanese JIS convention, 2SD parts are NPN bipolar transistors meant for low-frequency work. Even a short sheet normally gives ratings and pin assignment, the essentials for confirming a fault and choosing a compatible replacement. Match the package style with the original and look for D1555 printed on the body.
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.