PDF reference for the 2N3820, only 26.3 KB, likely a short one- or two-page data sheet, although the index files it as a schematic. The name gives just the JEDEC part number. Use it to identify the leads, check absolute maximum ratings and compare characteristics when testing or replacing the device. Since the part number may be produced by different manufacturers in different packages, confirm the case style and marking on the board against the drawing before soldering in a replacement.
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.