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.
Related Links
Transistor tester project
Transistor Checker circuit
Buzzer sound circuits
Test Transistor in Circuit by IC 4011
Checking Transistor with the sound
In Circuit Transistor Checker
Fast transistor tester circuits