How to Test Transistors

Good advice. I have run into transistors not working in circuit as they should. But I’ve also noticed breadboard discrepancies. I am buying expensive breadboards designed with better and stronger internal clips, and I’ve still noticed variations in their manufacturing. So I’ve wondered if the breadboard themselves weren’t sometimes to blame for these bad transistors. It’s concerning when you are building something large like this.

Would you be able to do a video explaining how the tristate buffers are constructed?

Something else I've noticed is you don't seem to be using base resistors between logic stages, only on the inputs. One priblem that can arise if you're trying to drive two or more transistor bases without individual resistors is Vbe clamping, where the transistor with the lowest Vbe clamps the voltage below the needed Vbe for the other transistors and "steals" most of the current, preventing the other transistors from fully switching on.

What is the name of transistor? 2n2222 or bt547 or other?

Use multimeter is easy!