Transistor alternatives and replacements (Pro-Electron, EECA, JESD370b) - Page 1
Forum section: electronics / projects

author: Cicada
author_rank: Regular Contributor
timestamp: May 20, 2022, 01:58:47 pm
content: HiI have to recreate an very old plugin card in a power supply. There are some transistors which I cannot source anymore. For example Motorola BU205Then there are some transistors like the Texas Instruments 2N4240 for which I can source the same part number from other manufacturers.https://octopart.com/search?q=2N4240&currency=USD&specs=0Click on the Manufacturers button to see (NJS, RCA, Microchip, Solid State Manufacturing)All these devices are named according to these naming standards "Pro-Electron a.k.a. EECA" or "JESD370b".This article describes the standards and gives a quick overview how the transistor codes are derived.https://www.electronics-notes.com/articles/electronic_components/transistor/transistor-codes-numbering.phpNow my questions.1. For the BU205 I will have to look for alternatives. Is there a online database of alternatives, website, app or any tool of any kind that can make this easier than comparing datasheets? Maybe even a paid service?2. For the 2N4240 I will have to buy a device from a manufacturer other than Texas I. Does devices with the same name have to have comparable/compatible specs? I.e. are these devices interchangeableCicada

author: Terry Bites
author_rank: Super Contributor
timestamp: May 21, 2022, 02:25:39 pm
content: These transitors abound on ebay at low prices. But make sure you test them first

author: Cicada
author_rank: Regular Contributor
timestamp: May 31, 2022, 02:51:03 pm
content: Relevant JEDEC documents can be downloaded fromwww.jedec.orgfree of charge after registration.UNDERSTANDING DATASHEETSJESD10.pdfThis standard define terminology and test methods for the transistor parameters listed in a typical datasheet. This is a great aid to understand transistor datasheets to identify alternatives.The index of this doc:1.2.3. Verfication tests3.1 Maximum ratings3.2 Safe Operating Conditions3.3 Electrcal Characteristics Tests4. Thermal Characteristics5.6.JESD10 refer tohttps://www.jedec.org/committees/jc-25You can also look at JESD77DTRANSISTOR NAMING CONVENTIONSJESD370b can also be downloaded from the Jedec site.EDIT. Sorry if this bump this post up again. I just wanted to add this link for my future reference.https://www.jedec.org/standards-documents/focus/registered-outlines-jep95/transistor-outlines-archive

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 31, 2022, 04:37:37 pm
content: I don't think any slow 1500V BJTs are still in production, especially in TO-3, so that one will have to be NOS.The whole point of part numbers is they're supposed to be interchangeable, compare datasheets (good idea to grab a period correct one) to confirm. There are some exceptions like the 2N3055, but that's a special case of a very early and poorly specified part that ended up having a very long life.

author: pardo-bsso
author_rank: Frequent Contributor
timestamp: May 31, 2022, 04:58:05 pm
content: Look into the NTE catalog for equivalences.Also in some places (like my country) you can buy NOS over the counter.

author: kripton2035
author_rank: Super Contributor
timestamp: May 31, 2022, 05:57:33 pm
content: 245 equivalents to the bu205 here :https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=10&ucb=1500&uce=700&ueb=5&ic=2.5&tj=150&ft=7.5&cc=80&hfe=2&caps=TO3

author: Cicada
author_rank: Regular Contributor
timestamp: May 31, 2022, 06:57:54 pm
content: Quote from: pardo-bsso on May 31, 2022, 04:58:05 pmI came across the NTE catalogue. Was not sure how to interpret what they are doing. I searched for BU205 on their website and found this result NTE165.https://www.nteinc.com/search.phpI am not sure if they manufacture their own semiconductors or if they take NOS from other brands and relabel it with their own number. The datasheet values look like it match those of the BU205https://www.nteinc.com/specs/100to199/pdf/nte165.pdfI wonder this company compares to Rochester which I think have a very good reputation. They also make devices from original silicon wavers that they have in storage. As far as I know they also manufacture old semiwaivers under license.

author: Benta
author_rank: Super Contributor
timestamp: May 31, 2022, 07:31:33 pm
content: Those transistors are nothing spectacular, typical parts of their era. One is 700/1500 V, the other 300 V. Look out for the switching specs.The big issue is, that TO-66 parts are unobtainium today, and TO-3 are few and far between.Good news is, that modern TO-3P (TO-218/TO-247) and TO-220 parts can be used as drop-in replacements, provided you snip off the middle lead.

author: strawberry
author_rank: Super Contributor
timestamp: May 31, 2022, 08:09:25 pm
content: KT838A TO-3 seems most popular USSR TV transistorsome transistors have built in resistors

author: Benta
author_rank: Super Contributor
timestamp: May 31, 2022, 08:31:27 pm
content: BU508A. Obsolete, but still available.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: June 01, 2022, 05:51:30 am
content: Time for a transistor curve tracer.Pic shows curves for an old (about 1974) BCY 79-9 (Aus UPGR)and a few new (2021) BCY 79-9 (Reichelt)

author: Cicada
author_rank: Regular Contributor
timestamp: June 07, 2022, 01:39:30 pm
content: Quote from: kripton2035 on May 31, 2022, 05:57:33 pmThis is exactly what I have been looking for. Enter the transistors parameters and get suggested alternatives. BUT... I think it might have been more relevant in the past since it seems that all alternatives are also not that easily available. Will of course be very handy if you have access to new old stock or if you buy from people that still stock these old devices.Thanks