PDF schematic labelled PA-1650-56LC, a code in the style used for 65 W class laptop power adapters, so it most likely covers an AC adapter circuit rather than a motherboard. The name gives no brand or further revision details. A power supply schematic helps trace the primary switching stage, PWM controller, feedback optocoupler and output rectification when an adapter is dead or unstable. Compare the label on the unit and the PCB markings with the drawing first, and remember that the primary side carries mains voltage and charged capacitors.
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.