Service manual for the Audio Pro B1.35 MK2 subwoofer, read from the B1_35MK2, sub and sm tokens in the name. The 307 KB PDF is fairly short, likely the amplifier schematic with a few layout or parts pages. Use it to check the built-in power amp, low-pass filter and Audio Pro's ACE-Bass circuitry, and to trace supply rails when the sub hums or stays silent. Make sure the MK2 version matches your unit, since earlier versions may use different boards, and discharge supply capacitors before probing.
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.