Substatuting transistors and ic's that are no longer available  - Page 1
Forum section: electronics / projects

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: September 18, 2015, 04:24:38 pm
content: Ok so.. i have this transistor that needs replacing and i cant get one anywhere because its from 40 years ago. Its a bfs97k. Anyone know how to find one that would work as a substitute? How would i find a substitute? I have some ic's to that need replacing but i cant get them anymore ether. How would i go about substituteing them as well. Thanks

author: singapol
author_rank: Frequent Contributor
timestamp: September 18, 2015, 04:54:22 pm
content: http://alltransistors.com/transistor.php?transistor=27920

author: The Doktor
author_rank: Regular Contributor
timestamp: September 18, 2015, 05:05:48 pm
content: This pagehttp://www.tehnomagazin.com/Transistors_data_and_replacement_tables/transistors_BF,BFAP,BFC,BFE,BFF,BFG,BFJ,BFN,BFP,BFQ,BFR,BFS.htmsays 2n1132. Remember that when substituting a component, some applications will be much more critical on matching the original characteristics than others. The best way to start the search is to go to Google, or whatever search engine you prefer, and type the part number followed by the word substitute and then try again with the word replacement.Note that if you are working with an old germanium transistor, it may be somewhat more difficult to replace. As to replacing ICs, that will depend very much on what type of IC and what type of circuit it goes into. In some cases, it may be as easy as replacing the old piece with an updated version. In other cases, there will be nothing else manufactured which even comes close, you will have to find the original or give up. The same method of searching through Google will work just fine here as well, if that fails you can always try here and hope somebody knowledgeable will have a decent answer.One other comment on seeking device replacements. You can try searching for information about the piece of equipment you need to replace the device in. Often you will find that other rather intelligent people have had the same problem, and have sometimes worked out fairly complex replacements which will work.Good luckEd

author: wraper
author_rank: Unknown
timestamp: September 18, 2015, 05:17:44 pm
content: Could use PN2907, BC327 and bunch of other general purpose transistors unless there are very specific requirements.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 19, 2015, 01:47:36 am
content: Quote from: wraper on September 18, 2015, 05:17:44 pmExactly!In many cases,you can say "Is it an NPN or a PNP?"-----"How big is it?",then find something which looks similar & try it.Another trick is to look up another manufacturer's similar circuit & see what they use.For example,BU208D's replace the "2S" series horizontal output transistors in many 1970s-80s Sony CRT TVs.(When you look at the schematic,it is almost the same as the Philips one)I often advise,if it is in a critical circuit,to look around the circuit,& see if they use the same device somewhere non-critical.If so,steal that one for the critical spot,& chuck a "similar" replacement in the other spot.

author: tautech
author_rank: Super Contributor
timestamp: September 19, 2015, 05:17:56 am
content: Quote from: Jesset1996.5 on September 18, 2015, 04:24:38 pmThe application where used is very important when sub'ing components, you don't say what it is.http://www.americanmicrosemi.com/information/spec/?ss_pn=BFS97K

author: vk6zgo
author_rank: Super Contributor
timestamp: September 19, 2015, 06:39:11 am
content: Ignoring the "k" suffix,"Radio Museum" has a page for it.http://www.radiomuseum.org/tubes/tube_bfs97.htmlThey give the BC338 as a near equivalent.

author: codeboy2k
author_rank: Super Contributor
timestamp: September 19, 2015, 11:36:56 am
content: Quote from: vk6zgo on September 19, 2015, 06:39:11 amYou typo'ed there. They give BC388, which is a PNP like the original. BC338 is NPN.However, BC388 is still not a true equivalent, I don't agree with them there. It has lower collector current Ic(about half as much as the original) and lower Vcb(again, half), and lower Pd. The Vceand Vebis about the same.It can work as a replacement if you know how the original is being used and that those parameters are not going to be exceeded. Even operating too near to those lower parameters would probably kill the replacement soon enough.

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: September 19, 2015, 05:25:48 pm
content: Quote from: codeboy2k on September 19, 2015, 11:36:56 amit goes to a prc -320 unit 5 which is its power supply. Its 110v rail stopped working and 3 transistors seemed to have been the issue. Tr1,2,and 3 all failed. Some say the ic is the issue but i tested it and it seems to be working just fine. I just got a transistor bfs97 which has similar specs. As for the iC's which are the cn587t and the cn 497t i have no clue where to find a replacement or substitute. Any ideas?

author: technix
author_rank: Super Contributor
timestamp: September 19, 2015, 05:27:20 pm
content: From the data available I think 2N2907 can go in there, or if you trust those even cheaper Made-in-China, SS8550.