[Solved] TSI361R - Identify obscure/old blown transistors - Page 1
Forum section: electronics / repair

author: zifk
author_rank: Newbie
timestamp: May 04, 2024, 05:38:15 pm
content: I got my hands on a fairly old and obscure frequency counter, the Apti-Meter 361R from transistor specialties inc.It's a beautiful piece of kit with a great nixie display.From the little information I can find about it (1), it's from the 1960s and is filled with Ge PNP transistors.It has a few issues that I'm trying to work through, and so far I've identified two transistors which are shorted.However, I can't find any information about the transistors themselves, as I believe they were custom, given the "TS" labeling on them. See highlighted cans on attached images. Both are labelled TS-1172, one additionally with 202 the other 208.Does anyone know how I can go about replacing these?(1)http://madrona.ca/e/edte/TSI361/index.html

author: floobydust
author_rank: Super Contributor
timestamp: May 04, 2024, 07:44:03 pm
content: Tung-Sol Electric TS-1172 I did a dig and have no data.I would consider generic PNP Si 2N2905, 2N2907 can (if heat diss. is important) or generic PNP Si plastic, or Ge if the circuit is critical about VBEfor 0.25VSome people find Ge transistors short due to tin whiskers (inside) and blow them out using a power supply.APTI Meters Instruction Book Models361,361R, 371, 371Rschematic, BoM etc.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2024, 07:58:50 pm
content: can you like treat those ge transistors somehow to cure them, maybe temperature ?

author: floobydust
author_rank: Super Contributor
timestamp: May 04, 2024, 08:03:23 pm
content: They zap the junctions to blow out tin whiskers, the germanium worshipers working on guitar effects pedals. Even pin-to-case.For OP, I'd just evaluate the circuit if it must be Ge or not, and prefer to put in Si replacements which beat them in most regards.Unless they want it all original.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2024, 08:13:11 pm
content: but maybe you can annel them or something like that to stabilize the wiskers formation

author: floobydust
author_rank: Super Contributor
timestamp: May 04, 2024, 08:49:51 pm
content: Annealing tin seems pretty hot 230-300°C? and where does it go? Fall inside I guess.More pics here:NASA Anecdote: Tin Whiskers Inside of AF114 TransistorsThey recommend tapping on the top, yeah beat up that transistor's whiskers lol

author: fzabkar
author_rank: Super Contributor
timestamp: May 04, 2024, 09:06:06 pm
content: Some historical stuff here:http://semiconductormuseum.com/PhotoGallery/Photogallery_Tung-Sol_Historic_Germanium_Computer_Transistors.pdfQuote

author: zifk
author_rank: Newbie
timestamp: May 04, 2024, 09:35:31 pm
content: Thanks for all the info! Flood especially, I'm amazed you found that book, I searched long and hard for something like that. I have some nice reading ahead of me.I'm fairly certain I toasted these two transistors. Luckily I'm fairly certain they don't play any critical black magic roles. The instrument was mostly working fine and counting beautifully until I went poking inside trying to figure out why the front reset button wasn't working. Otherwise, most of the transistors seem to be functioning just fine, so I doubt it's an age thing.As best as I can tell, these two simply switch the ~-9V level used for the transistor logic, so I'll probably try some Si replacements after analyzing the schematic a bit more.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2024, 10:31:42 pm
content: Quote from: floobydust on May 04, 2024, 08:49:51 pmI was thinking more along the lines of maybe some how treating it to prevent future regrowth, after their vaporized. maybe you can relax the material some howlike with carbon comp you can bake them to regain their performance. that is much simpler system but the concept is the same

author: zifk
author_rank: Newbie
timestamp: May 09, 2024, 05:20:01 pm
content: Well after swapping out the two suspected failures with some 2N4403 Si PNPs, everything is back up and running! Thanks for all the help and advice.