How do I know if a transistor is a 2N4401 or a 2N3904, etc?

Good day. I'm a newbie scavenger, and I scavenge parts since I don't have enough money to buy new parts. I want to know if the transistor i found is a 2N4401 or a 2N3904 or another? I can't find it in the Internet. One thing I know is that it's an NPN transistor. I also noticed some numbers on the flat side of the transistor. Does it help in determining the transistor? Thanks in advance to those who will answer. :D

These transistors will have their number written on the back/flat side of the transistor.

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CarlGemarino (author)  Jonathanrjpereira2 years ago

Hi. Thanks for answering, but I am confused, the transistors I found don't have printed numbers like that, instead they're "S9015 C 331", "S8050 D 331", "13003 HJ E1D LTC00E", "13003 HJ E1D LTC0XX". What does those mean?

Quite often those a secret markers put on by manfacturers who have the buying power to have devices numbered with their own codes. SOMETIMES you can find them by net searches, they might be Chinese or other far eastern makers who don't use the same nomenclature as JEDEC.

Davinci2K17 months ago

HI am a big scavenger myself - desoldered a couple of these 331's as well. According to this alibaba page its an NPN: https://www.alibaba.com/product-detail/NPN-transistor-S9014-C9014-C331-TO_60288531459.html So it should be Emitter, Base and Collector