Lenovo B490 laptop schematic, a 1.95 MB PDF whose name gives no board number or revision. Look at the title block inside to find the ODM project and board number, then confirm it matches the marking on the motherboard, since one model may ship with different boards. With a match, the drawings help follow standby and main power rails, read the power-on sequence, locate test points and identify parts around a short or a missing voltage. Any PDF reader opens it and can search for signal names.
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.