Old old very old electronics...

[xenoxaos]

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.

[BrokenYugo]

Looks like an RF choke (inductor) to me.

[Bud]

I do not think resistors are wound in that manner. Inductor then.

[IanB]

Time to find out that you just destroyed a valuable item that fetches huge sums on the antique restoration market 

[Bud]

Has anyone ever come across something that looks and feels like a rock with a pair of leads coming out?

Yes, seen inductors, diodes and varicaps in this droplet format. It is fascinating what you can find in pre-WW2 radios.

[xenoxaos]

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.

[xenoxaos]

Time to find out that you just destroyed a valuable item that fetches huge sums on the antique restoration market 

I just happen to have another rock with wires for you!

[vk6zgo]

I do not think resistors are wound in that manner. Inductor then.

Yep!  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".

[CatalinaWOW]

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. 

[CatalinaWOW]

I do not think resistors are wound in that manner. Inductor then.

Yep!  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".

Actually 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.

[rsjsouza]

I do not think resistors are wound in that manner. Inductor then.

Yep!  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".

"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. 

[Quarlo Klobrigney]

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.com Sorry no SSL link

[vk6zgo]

I do not think resistors are wound in that manner. Inductor then.

Yep!  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".

Actually 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.

If 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.

[Wallace Gasiewicz]

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.

[TimFox]

I do not think resistors are wound in that manner. Inductor then.

Yep!  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".

Actually 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.

If 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.

The "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

[xenoxaos]

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.

There 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.

[wasedadoc]

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.

Ahem! Inductors are not characterised in capacitance units!

[vk6zgo]

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.

There 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.

Asbestos has poor dielectric properties, so it is very unlikely.

[Wallace Gasiewicz]

I deeply apologize obviously uH not Farads.Sorry