The 2SK2504 transistor is documented in this 134 KB PDF, named in lowercase and catalogued under schematics. Its 2SK prefix follows the Japanese JIS scheme for N-channel field-effect transistors; no maker is given. A variant file carrying a _1-5 suffix is of nearly identical size. Read the pin assignment, drain-source voltage and current limits here when diagnosing a failed switching stage or choosing an equivalent, and verify the part code on the original device before relying on it.
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.