Transistor Tester

This tester is intended to quickly check whether a transistor is functional or not and possibly also select two or more transistors with (approximately) equal gains. This is about the simplest conceivable test circuit, so don’t expect super accuracy. The circuit has been designed only to quickly carry out a brief check, when there is no time or equipment to carry out a thorough test.The operation is simple: in the position ‘battery test’ (S2 closed), the 10 mA moving coil meter M1 in series with a 600 ? resistor (R4 + R5) is connected to a 6 V battery. A current of 10 mA will flow, resulting in full-scale deflection of the meter.