1, first turn the multimeter to the diode measurement file;
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2, the black watch pen is connected to D (drain), the red watch pen is connected to S (source), at this time, there should be a pressure drop of 0.2~0.5 normally, and the multimeter displays figures between 0.2~0.5;
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3, the black watch pen is connected to S (source), the red watch pen is connected to D (drain), this should have no pressure drop, the multimeter shows OL or 1;
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4. The black watch pen is connected to S (source), and the red watch pen is loosened after touching G (grid);
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5, the black watch pen does not move, and then use the red watch pen to connect D (drain), there should be a small voltage drop (multimeter shows a number of about 0.1 then this crystal field effect tube is good;