# Finding Equivalent Transistors (BC178 and 2N2646)

I have an old schematic which uses two obsolete transistors, the BC178 and the 2N2646.

By searching I was able to find that the BC178 can be replaced by the BC177 as written on this page: http://www.el-component.com/bipolar-transistors/bc178

I haven't been able to find an equivalent for the 2N2646. I did find a page that appears to let you enter in the specs of the transistor and it will list equivalents, but I am not well versed in transistors to understand how to use the cross-reference calculator which is available here: https://alltransistors.com

I was expecting it to be easier to find equivalent replacements for these older obsolete devices, but it seems to be difficult.

Can anyone please provide me information as to how I can find replacement parts for these two transistors, and guide me towards resources to make it easier to find equivalents in the future?

I exhausted my search capabilities on google searching for "replacement" and "equivalents" of those two devices. It is overwhelming to me the numerous number of transistors and I am struggling to understand the very small differences in spec.

Thank you in advance for your wisdom!

• 2N2646 is still on sale in the UK. One supplier is Farnell who list it here. Another site claims that the following are equivalents 2N2647, 2N4870, 2N4871, 2N1671 – Peter Jennings Sep 12 at 0:21
• It's sort of contradictory that you're asking for equivalent parts even though you mentioned that you're trying to find equivalent replacements for these older obsolete devices. I think what you need to do is review your specs and see what device that can help you accomplish your goals with your specs. Older technology may be able to help you reach your specs. So as of right now, this question is too vague since you don't have your specs listed out and we can't really know what you are thinking when choosing one product over another. Why do you need something that is "not obsolete"? – KingDuken Sep 12 at 3:17
• The main reason why I wanted something “not obsolete” was for cost purposes. Paying $3+ for a transistor seems like too much. – Nate Houk Sep 12 at 3:25 • Well manufacturing companies usually purchase bulk amounts of transistors because it's cheaper that way when they prepare their BOMs for factory and supply chain. ~$3 USD actually sounds very reasonable for a single transistor. If they sold it any cheaper, it would be more expensive to ship and create than to sell and the supplier would lose money because of shipping costs and fabrication processes to make that single transistor. Transistors are more expensive per unit the less you buy because they wouldn't be able to make a profit otherwise. – KingDuken Sep 12 at 4:42
• BC17x can be also replaced by BC857 in suitable package. But the UJT (2n2646) is not much used anymore, the functionality being more reliably achieved using newer better devices. What does your circuit do? – Soldersmoke Sep 12 at 5:02