Schematic in PDF identified only as NS4KU01 with a VB tag and a timestamp of 17 April 2017, 09:00. The name gives no brand or board number, so the model must be confirmed from the title block. Such diagrams are used to trace power rails, follow signals between chips and find components around a fault. Open it in a PDF reader and compare the project name and revision against the PCB markings before measuring against expected 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 @afsschematicfree. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)