This 260 KB PDF labelled 1B51 is catalogued as a schematic, though the short code more likely names a discrete component and the file is probably its datasheet. Nothing else about device, package or maker appears in the name, so open it and check the header. Datasheets like this provide ratings and outline drawings needed to verify a replacement part. Any PDF reader works; compare the marking on the board component with the document before using its values.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)