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

About Dino

Self taught electronics and hardware hacker.
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One Response to Simple Transistor Tester

  1. rbwilliams says:

    Hey Dino, glad to see you weathered the storm.

    Another thought on this: some Japanese transistors have the pins in different configurations (not just backwards). One could wire up a few more configs in parallel put the transistor into.

    Also, Harbor Freight sells an incredibly cheap and decent multimeter with a tester built-in:

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