Short 100 KB PDF datasheet for the STK465, a thick-film hybrid audio power amplifier module from the Sanyo STK range. It should show the pin layout, supply voltage limits, output power figures and a recommended amplifier circuit with external components. Audio repair technicians use it to check the split supply rails, find the input, output and feedback pins, and confirm a dead or distorting channel. Such hybrids often fail shorted, so measure the supply pins to ground and check the speaker protection before powering up a replacement.
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 @datasheet_technar_org. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.