The 2SD1800 transistor is covered by this 79 KB PDF datasheet. Under JIS numbering, 2SD denotes an NPN transistor for low-frequency service, often used in switching, driver or regulator circuits. The document gives ratings tables, characteristic curves and a pin diagram, letting a technician confirm lead function before testing and select an equivalent with matching voltage, current and gain. Check that the package on the board matches the drawing, because similar parts may ship in different cases.
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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