The 2SB1642 PNP transistor is documented in this 181 KB PDF, listed as a schematic though it is a part datasheet. The 2SB designation follows the Japanese JIS standard for PNP low-frequency bipolar transistors; manufacturer and package are not given in the name. Use it to verify pinout and limits when testing the device out of circuit with a multimeter diode range, or when sourcing a replacement. Pay attention to the gain grade letters and package dimensions so the substitute fits the footprint and behaves the same.
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 @cyberlanelectonik. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.