How do I determine what kind of transistors I have salvaged?

[electricguru]

Hey, I have a ton of of loose transistors with random markings. I was just wondrin how I can determine their bias point, whether they are PNP or NPN, and their transistor number (like 2N3906).

 

[cr0sh]

First step is to sort them and note their numbers (for each pile/group).

Then do some googling with "#### datasheet", where #### is the number or portion of a number you wrote down. Hopefully, you'll find most of the datasheets this way, which will have all the other information you need.

Those that you don't find datasheets for - may either be so old that you can't find them online, or they are "house numbered" - meaning a company bought them for internal stuffing of boards, and had the manufacturer mark them with their own numbering scheme, only known to them. Good luck figuring those out. Sometimes the house number may be a variation on the real number (for instance, if it contains "3904", then it may be a 2n3904 - if it is in the right case; the case style can also be a clue).

You'll eventually end up with an "unknown" pile - house marked or otherwise. From there, you can sort them into NPN/PNP by doing some transistor and diode checking with a multimeter (look online for details). Some, though, may not even make sense with this test (I have some large TO-3 case "transistors" that don't make any sense; for all I know they aren't transistors - they may be MOSFETs, or voltage regulators, or? Many things come in cases similar to transistors, so keep that in mind).

I don't know if there are other options that I haven't covered, but that is the procedure I have always used to find out what part is what (passives, actives, and ICs); unless you are really unlucky, you can generally expect to find 80 percent of what have online. Just be prepared to spend a lot of time in front of the computer...

Good luck.

 

[electricguru]

thank you very much!

Ω