Yamaha PA 2400 amplifier schematic in a small 194 KB PDF. The name gives no revision or note about modifications, so it may represent the standard circuit, but confirm against the unit. A repairer uses it to trace the input stage, driver and output transistors, protection and power supply, check bias settings and identify blown parts after an output failure. Compare part designators and values with the actual board, since clones and modified builds of this design are common.
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.