Labelled only 123nq, this 98.5 KB PDF is catalogued as a schematic but names no device, board or revision. The short code looks like a power-rectifier series designation, suggesting a component sheet covering multiple voltage variants. A PDF reader is all that is needed. Such a reference helps when measuring a suspect part in diode mode or choosing a replacement with adequate ratings. Since the series code alone does not fix the voltage grade, confirm the complete marking on the component.
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.