The 174 KB PDF named 400CNQ is filed under schematics but its name carries no model or board number. Lacking a suffix, the code most likely denotes a whole semiconductor family, so the datasheet probably tabulates several voltage grades sharing one package. Expect terminal layout, maximum ratings, thermal data and outline drawings. Useful for identifying the common terminal in a dual rectifier module and choosing a correct replacement. Match the printed part marking against the variant list before ordering a substitute.
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.