Sony M850 project archive covering two board numbers, MBX-217 and MBX-216, with the release code 1-01, about 824 KB. Sharing one document suggests the two boards are closely related variants of the same design. The schematic inside helps trace power rails, check signals and identify components around a short. Since the two variants may differ in populated parts, compare the board number and revision on your PCB with notes in the drawings before measuring or swapping components.
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 @generalschematics. 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.