The 3SK219 is covered by this compact PDF of roughly 30 KB, indexed as a schematic but by its name a part datasheet. Under the JIS convention, 3SK identifies four-lead field-effect transistors, commonly dual-gate MOSFETs for RF gain-controlled stages in radios and TV tuners. A repair technician would consult it for leg order, absolute maximum voltages and typical application values. Any PDF viewer opens it; verify the package type on the board matches before soldering in a part listed here.
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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.