The 2SD1628 is covered in this 88.3 KB PDF, catalogued with schematics though it relates to a single transistor. Under Japanese JIS numbering, 2SD identifies an NPN bipolar part for low-frequency or power applications. A sheet like this generally gives maximum ratings, characteristics and pinout. Use it to determine which lead is which in the package, verify limits, and judge a cross-reference substitute. Match the component marking first, as package variants of one number can differ in pin arrangement.
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.