Matrix 1.4 amplifier document tagged WS3, likely a variant or board revision label, in a 978 KB PDF. The name does not state power rating or load. It probably holds the schematic or PCB layout, useful for placing components, tracing the input differential pair, voltage amplifier and output stage, and checking bias settings. Open it in any PDF viewer, compare designators with your physical board and verify supply voltage limits before building or replacing transistors on this Matrix variant.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.