I would like to take the switch out of the circuit. The circuit will remain open, until the transistor is applied to the socket, in the correct orientation. When the transistor finds the correct orientation, the circuit is closed, the LED lights, the transistor is proved and it is identified.
As the transistor is moved from one position to the next, it will be exposed to incorrect power, until it reaches the proper position. Is a small dose of incorrect power (3v3) likely to significantly stress, or damage, the transistor? I am sure that it is not recommended, by the manufacturer, but, from a practical stand point, is it truly an issue? Don’t all testers work this way, by some manner?
Proposed Transistor Tester Instructions
For unknown transistors...
Attach the battery. Orient the face of the transistor toward the NPN side. Apply the transistor legs to the top three socket spaces. If the LED does not illuminate, move the transistor legs to the lower three socket spaces. If the LED does not illuminate, move the transistor to the PNP side.
Orient the face of the transistor toward the PNP side. Apply the transistor legs to the top three socket spaces. If the LED does not illuminate, move the transistor legs to the lower three socket spaces.
If the transistor type is known, from the start, just test it on its type side.
When the LED illuminates…
If it is facing the NPN side, it is a NPN transistor. Take note of the alphabetic code coinciding with its legs. This is their pin assignments.
If it is facing the PNP side, it is a PNP transistor. Take note of the alphabetic code coinciding with its legs. This is their pin assignments.
If the component does not cause a LED to illuminate, in any of the tested positions, the transistor has either failed, or the component is not a transistor.
Alphabetic Code
E = Emitter
B = Base
C = Collector
E = Emitter

