Final PCB artwork for an amplifier using Sanken output transistors, labelled 7 set, which likely indicates seven pairs of output devices, delivered as a large 7.42 MB PDF. Sanken parts such as their audio power transistors are common in high-power DIY designs. The file supports building the board, locating transistor positions and tracing emitter resistors and supply rails during repair. Print at full scale, measure a known footprint first, and use matched genuine devices since counterfeit output transistors are a frequent failure cause.
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.