Schematic PDF for Apple logic board 820-3435, with a b in the name that may indicate a variant or revision, 1.45 MB in size. The 820-xxxx number is printed on Apple logic boards, so compare it and the revision before relying on the drawing. Technicians use it to trace the power path from the charger through each regulator, follow SMC and power-good signals and check expected voltages when a machine fails to power on or charge.
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 @one5technology. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)