Help finding parts - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: September 10, 2022, 11:27:57 pm
content: I need to find the following parts and as easy as it is for some I’m new and can use the help.

author: exmadscientist
author_rank: Frequent Contributor
timestamp: September 11, 2022, 08:21:14 am
content: Going by color, a few things that should work...Goldis just a 1N4007 diode (or 1N4004, or anything in between, I guess), no problem.Redis a bit of an issue as I don't see anything through-hole that's actually specified right at 20mA. But 25mA should be fine (it's just a zener...) and that's done by BZX85C8V2. That's a standard part made by a few manufacturers and so you can always buy several and bin them if you really care. (I wouldn't.)Blueshould actually read "1N816". This guy is weird enough that I'm out of time to track it down. It looks resolvable, though?Greenis also weird, since 2.2V zeners are, ah, never Designer's Choice. (It's not the best choice, it's Designer's Choice?) But taking it at face value, PLZ2V2A would do it exactly if you could tolerate surface mount. I don't see a great option for through-hole. Few vendors are crazy enough to offer a zener down at 2.2V, and none crazy enough to specify it at 20mA. There are 5mA parts in the market (BZX55C2V2 R0G, BZX79C2V2 R0G) which might be OK. If you have the schematic you can probably figure out what's going on and either build a replacement subcircuit (not too hard) or finesse it. You don't show the schematic, but you're going to need it, because of...Purple. Purple is going to be some work. The 2N5457 is obsolete. You can probably find one, or find something close enough, and you can probably find that something in a metal can if you want that (the image kinda-but-not-really suggests you do). But "selected"? Selected forwhat? It's a JFET, their parameter spread isawful, you have to select them for just about everything if it's precision work. Which parameter is important here, and what does it have to be or match? Good luck!

author: ledtester
author_rank: Super Contributor
timestamp: September 11, 2022, 09:17:52 am
content: You should also give us the link to the complete service manual because that gives us a lot more information like what the device is, what it is supposed to do and a schematic.The device appears to be a Sencore TC154, and the service manual may be found on this page:https://vintagetubeelectronics.com/tube-tester-manuals/at this link:https://vintagetubeelectronics.com/wp-content/uploads/2019/03/Sencore-TC154-Service-Manual.pdfHowever, the service manual there for the TC162 has a very similar parts list and schematic and is a lot more readable so you'll probably want to follow that one.For instance, it is clear from the TC162 schematic that CR3 (the "IN816") is a protection diode for the meter so I would guess that a 1N916 or 1N4148 would work there.

author: Crambone
author_rank: Frequent Contributor
timestamp: September 12, 2022, 02:34:00 pm
content: Yes it’s a TC154 I got for free but a few parts are missing and those diodes are among them. I had the resistors and capacitor and everything else checks good.Drew