The 1SR156-400 document is a 120 KB PDF catalogued as a schematic, though its name follows a discrete component part-number style and carries no device or board reference. The 400 suffix appears to designate one variant of the part. Use it as a reference sheet for pin orientation, maximum ratings and footprint when diagnosing a shorted or open component or picking an equivalent. Readable in any standard PDF viewer; always verify the marking on the actual part before relying on the listed data.
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.