Spanish electronics learning series El mundo de la electronica, issue 21, in a PDF of about 1 MB. The title names no device or board, so it should be treated as general theory rather than a repair schematic. Volumes in a numbered course like this typically explain component behaviour, circuit analysis and practical projects in steps. Open it in any PDF viewer. It is handy for technicians reinforcing fundamentals such as reading circuit diagrams and understanding how stages in a power or signal path work.
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 @canalesquematicos. 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.