Schematic in PDF for the Apple MacBook model A1398 with logic board number 820-00138, 1.5 MB in size. A1398 is the 15-inch Retina MacBook Pro, and 820-xxxxx is Apple's own logic board numbering. Diagrams like this show the power architecture, SMC and charger circuits, letting a technician follow rails like PP3V42_G3H and check enable signals. Pair it with a boardview to locate parts physically, and confirm the 820 number printed on the board matches before relying on values.
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 @IT_SERVICE_WORLD. 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.