Schematic PDF named tc21z80pq, 1.89 MB in size. The name carries no brand, model, board number or revision, so the content must be checked by opening the document and comparing the title block with your board. A schematic of this kind is used to trace power rails and signal paths, read component values and find where a fault such as a short or missing voltage originates. Confirm that the board number and revision in the drawing match the printed PCB before relying on it.
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 @pdf_servicemanual. 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.