The 3SK270 semiconductor is described in this 32.7 KB PDF, listed as a schematic although the content is expected to be a part datasheet. Only the number appears in the name. Japanese JIS numbering reserves 3SK for N-channel FETs with four leads, which are largely dual-gate MOSFETs for RF use. Look here for the terminal arrangement, package drawing and electrical limits before ordering an equivalent, and observe antistatic handling because the insulated gates are easily damaged.
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.