Schematic diagram in PDF for the IBM ThinkPad R40, roughly 1.45 MB; the name gives no board number or revision. IBM-era ThinkPad drawings typically use IBM page numbering and FRU-oriented labelling. The document helps trace power rails, check the charger and power switch logic, locate components and follow signals to connectors when diagnosing an older ThinkPad. Several R40 sub-variants exist, so compare the planar markings and chips on the board against the schematic before trusting values.
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 .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.