The 2SC5421 transistor is the subject of this 323 KB PDF, likely a datasheet since 2SC stands for a JIS-registered NPN bipolar device. The name supplies no other information such as package or manufacturer. Expect pinout drawings, absolute maximum ratings and characteristic curves useful for circuit analysis. Before ordering a replacement, compare hFE grade suffixes and case type with the original part, as small differences can affect switching and amplifier stages in repaired equipment.
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.