Apple logic board 820-3209, revision A, supplied as a 2.60 MB RAR archive with no model or content details in its name. Apple's 820 numbering identifies its in-house board designs; read the number and revision off the PCB to confirm the match. Expect a schematic and possibly boardview data, opened with a PDF reader or OpenBoardView. These are used to understand power sequencing, find which rail is missing or shorted, and locate the components and test pads involved.
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 @Mac_Shematic_Santale. 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.