Simple Transistor Tester

This is basically a high gain amplifier with feedback that causes the LED to light and flash at a rate determined by the 10u and 330k resistor.
Remove one of the transistors and insert the unknown transistor. When the transistors are inserted with the pins in the correct position as shown in the photo, the LED will flash. To turn the unit off, remove one of the transistors.

Parts list:

1 – 10 uF polarized capacitor
1 – 1K ohm resistor
1 – 330K ohm resistor
1 – 22 ohm resistor