PDF sheet for the 2SK1233 MOSFET, size 46.1 KB, part of the Japanese 2SK series of N-channel field-effect transistors. Only the bare part number is given in the name, so check the marking and package of the device on your board. Inside you should find maximum ratings, electrical characteristics and a pin layout. Use it to identify terminals for diode-mode testing, confirm a failed junction, and compare voltage and current specifications when selecting a modern substitute.
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.