Transistor quality checker with buzzer

You checked the transistor by measuring the resistance between the different pins. Sometimes it has problems, such as when measuring the resistance between the various legs correctly. But it does not work in the real circuit. Because while there is no measurement bias junction between CE. therefore, the detection transistor good or bad for sure. the transistors must be forward. and reverse bias at the same time. Injection of the electron, or hole between the junction. This circuit is a test. So, using the actual circuit. If the transistor test “good” circuit is the audio source it.

But if bad transistor. Integrated audio source will not come out. Or a very quiet voice. This circuit of operation of the simple astable transistors test to run during low flows about 20 mA,and transistors are tested to work with Q1 to generate frequency of about 2 KHz. the transistors Q2 expanding output to a buzzer. The switch S2 acts during the type test transistor NPN or PNP, the switch S1 using the press to test transistors.
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