Logic board schematic in PDF form for the Apple J113 project, which corresponds to a MacBook Air model; the name gives no board number, so confirm the 820- number before relying on it. The 1.29 MB RAR provides circuit diagrams for power rails, charging, SMC and other subsystems. Technicians read it to understand power sequencing, find which rail is missing and identify parts to measure. Pair it with a matching boardview for physical locations, and check the revision of the drawings against the board you are repairing.
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 @schematicslaptop. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.