Archive for Apple logic board 820-2936, revision A, packed as a 1.74 MB RAR; the Mac model is not stated. Apple uses 820-xxxx numbers on its logic boards, and the number is printed on the PCB, so match it before use. The lb prefix suggests logic-board material, but the contents should be checked after extraction for schematic or boardview. Such files help trace power rails, locate test points and diagnose shorts on Mac boards. Boardview files usually open in FlexBV or OpenBoardView.
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 .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.