Old old very old electronics... - Page 1
Forum section: electronics / beginners

author: xenoxaos
author_rank: Contributor
timestamp: September 22, 2023, 09:57:03 pm
content: Has anyone ever come across something that looks and feels like a rock with a pair of leads coming out? My LCR didn't know what to really make of it between an R and L. So I got out the Wilderizer and here's the results.

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 22, 2023, 10:02:32 pm
content: Looks like an RF choke (inductor) to me.

author: Bud
author_rank: Super Contributor
timestamp: September 22, 2023, 10:05:42 pm
content: I do not think resistors are wound in that manner. Inductor then.

author: IanB
author_rank: Super Contributor
timestamp: September 22, 2023, 10:18:22 pm
content: Time to find out that you just destroyed a valuable item that fetches huge sums on the antique restoration market

author: Bud
author_rank: Super Contributor
timestamp: September 22, 2023, 10:22:14 pm
content: Quote from: xenoxaos on September 22, 2023, 09:57:03 pmYes, seen inductors, diodes and varicaps in this droplet format. It is fascinating what you can find in pre-WW2 radios.

author: xenoxaos
author_rank: Contributor
timestamp: September 22, 2023, 10:28:45 pm
content: By droplet format you mean cast into random shaped rocks? I've seen some of these in the past and just chucked them. I just got two more and decided to take a crack at them. I always figured it was some component that leaked and over time oxidzed whatever came out.

author: xenoxaos
author_rank: Contributor
timestamp: September 22, 2023, 10:29:35 pm
content: Quote from: IanB on September 22, 2023, 10:18:22 pmI just happen to have another rock with wires for you!

author: vk6zgo
author_rank: Super Contributor
timestamp: September 22, 2023, 10:45:00 pm
content: Quote from: Bud on September 22, 2023, 10:05:42 pmYep! Plain old "Pie wound RF choke". (Googling, they appear as "Pi-wound", but the name has nothing to do with the mathematical symbol)Most of them aren't encapsulated, so I would guess it was of Military origin as an attempt at "Tropicalisation".

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 23, 2023, 01:55:25 am
content: I don't think I have any around now, but used to see similar stuff in pre-WWII radios from the US. The ones I recall seeing had a coating that was more closely fitting to the coil form/resistor and coil, but evidently in your area they dipped them in a more viscous potting compound.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 23, 2023, 01:58:11 am
content: Quote from: vk6zgo on September 22, 2023, 10:45:00 pmActually it is loosely related to the mathematical symbol. The schematic vaguely resembles the greek letter pi. You will sometimes see the term tau filters, with the same reasoning. Most folks just call them T-filters.

author: rsjsouza
author_rank: Super Contributor
timestamp: September 23, 2023, 02:24:18 am
content: Quote from: vk6zgo on September 22, 2023, 10:45:00 pm"Tropicalization" indeed. In Brasil chokes in this protective resin layer were the most common type, including mass market radio sets. Imports usually didn't have this cover, though.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 23, 2023, 06:40:40 am
content: Before the epoxies, there was Glyptal.Sprayed in all the electronics going to the jungles to prevent "Jungle Rot" especially in WW2.It's been around since Edison's time and what a mess it was to work on electronics treated with the after the stuff dried.I preferred the epoxy dipped components when they developed the process (orange drop caps come to mind). Sorry tantalums, no need to apply....http://www.glyptal.comSorry no SSL link

author: vk6zgo
author_rank: Super Contributor
timestamp: September 23, 2023, 08:23:33 am
content: Quote from: CatalinaWOW on September 23, 2023, 01:58:11 amIf you ignore the stray capacitance to the common rail, it just looks like a plain old inductor.As far as I can determine the term was "pie", because the flattish shape of the "lattice wound" coil resembled that of a pie.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: September 23, 2023, 12:16:41 pm
content: I just replace one of those "chokes" in a Yaesu FT 101 with a modern variety. The FT 101 is not that old.Part was identified in the manual.Yes they are inductors,That one is probably about 200 uF. Your markings are burned off but markings were paint dots on mine.

author: TimFox
author_rank: Super Contributor
timestamp: September 23, 2023, 05:28:28 pm
content: Quote from: vk6zgo on September 23, 2023, 08:23:33 amThe "pi" winding technique for RF chokes (e.g., 1 mH) is used to reduce the parasitic self-capacitance of the inductor and thereby raise the self-resonant frequency.It is better for that purpose than a multi-layer solenoidal winding.Illustration of obsolete part (you can't get good stuff anymore):https://www.digikey.com/en/products/detail/bourns-inc/4652-RC/3193280

author: xenoxaos
author_rank: Contributor
timestamp: September 23, 2023, 09:08:45 pm
content: Quote from: Wallace Gasiewicz on September 23, 2023, 12:16:41 pmThere was no markings on the outside of the 'rock' part of it. I didn't even look for any color codes. I was more "why a rock?" I'm actually wondering if there's asbestos in these things.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 23, 2023, 10:37:07 pm
content: Quote from: Wallace Gasiewicz on September 23, 2023, 12:16:41 pmAhem! Inductors are not characterised in capacitance units!

author: vk6zgo
author_rank: Super Contributor
timestamp: September 23, 2023, 11:28:39 pm
content: Quote from: xenoxaos on September 23, 2023, 09:08:45 pmAsbestos has poor dielectric properties, so it is very unlikely.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: September 24, 2023, 12:19:39 am
content: I deeply apologize obviously uH not Farads.Sorry