PDF schematic named only SY3, a 551 KB document without any brand, model or revision information in its name, so its identity must be confirmed from the title block inside. As a circuit diagram it serves for tracing power rails, finding the components on a shorted net and checking signal routing between controllers. Open it with any PDF reader and use search for net names. Compare the board code shown in the drawing with the markings on the PCB before taking measurements against it.
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.