This circuit is built around an oscillator. When the transistor tests good, the oscillator will produce a tone in the speaker.
Parts List
Unless otherwise stated, resistor wattage = 0.25W.
R1 = 150Ω
R2 = 220KΩ
R3 = 150KΩ
C1 = 100nF
C2 = 47nF
D1 = 1N4148
T1 = BC557
T2 = BC547
SW1 = DPDT...