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Mystery part - what is this?

Discussion in 'Discussions, Opinions & Editorials' started by W7UUU, Feb 4, 2013.

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  1. W7UUU

    W7UUU Premium Subscriber QRZ Page

    I've been dinking with electronics since I was 8 (I'm 51 now). I've taken apart
    a bunch of gizmos over the years for parts to use in other projects.

    But this one has me stumped.

    I bought a chassis on eBay (sweep generator) for the parts within. It had a lot
    of cool retro bits to use in some homebrew projects - which is good, because
    its days as a sweep generator were long past - lots of deterioration except for
    the parts I was after (National verniers, power transformer, choke, etc.).

    This gizmo was on a fairly sophisticated homebrew chassis - see photos. One
    tube on top... VHF coil on the top as well. What you see in the first photos is
    just a small subassembly of the larger unit. I removed the subassembly for
    the photo.

    I have NO IDEA what this is.... and it's driving me nuts! :D:D

    Weighs about 2 pounds, is mildly magnetic (see how it loves tube shields!),
    and most interestingly (to me) is that the only terminals on it, on the top,
    have ZERO DC CONTINUITY! That rules out a coil of any type that I can
    think of ... or transformer ... Diameter is 2.5", about 2" tall.

    It also appears very sealed - think "Military" - thick brown glue on every screw
    and every possible entry point.

    What the hell is this thing? And why would it be in a sweep generator homebrew
    project from the 1950s?


    Attached Files:

  2. KL7AJ

    KL7AJ Ham Member QRZ Page

    Anyone can tell you it's a "doohickey". But more precisely, it's a rotary switch doohickey.
  3. K8ERV

    K8ERV Ham Member QRZ Page

    Motor driven capacitor to sweep a hf osc?

    Whatever it is, that's it.

    TOM K8ERV Montrose Colo
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

    No...actually, it's a SATURABLE reactor swept oscillator. This is how you did it before the Varactor diode was around. You force more or less DC current through one winding of a core, which changed the inductance of the other winding. A fixed magnetic field "biased" the reactance into its linear range. It took quite a BIT of DC current to do this...which is why the resistance you measured is so low.

  5. KB1NXE

    KB1NXE Platinum Subscriber QRZ Page

    Early Flux Capacitor. I think version 1.2 or there abouts. Only .000001200 jigawatts...
  6. KL7AJ

    KL7AJ Ham Member QRZ Page

    Or a Clux Fapacitor
  7. W7UUU

    W7UUU Premium Subscriber QRZ Page

    But it has ZERO DC continuity, and only 2 terminals.... ???

  8. N2EY

    N2EY Ham Member QRZ Page

    It's a wobbulator.

    73 de Jim, N2EY
  9. KL7AJ

    KL7AJ Ham Member QRZ Page

    Should have at least a couple more terminals on the top, where the oscillator connects. You should be able to take the "can" apart and see the toroid inside.

  10. W7UUU

    W7UUU Premium Subscriber QRZ Page

    Yes - I now realize the phenolic board has ONE terminal on it as well....

    I'm going to open it up right now to see what's inside :D:D:D

    Hopefully it's not the "well of souls" and when I open it, my face will melt and what not....

  11. K8ERV

    K8ERV Ham Member QRZ Page

    Wear safety glasses.

    And remember, it is the GREEN wire!

    TOM K8ERV Montrose Colo
  12. KL7AJ

    KL7AJ Ham Member QRZ Page

    Be sure to wear your tin foil hat and-or hazmat suit. I'm sure there's come cold-pressed Latinum in there.
  13. W7UUU

    W7UUU Premium Subscriber QRZ Page

    OK... so I opened it up (yes, a few weak souls escaped but my face did NOT melt!)
    (and YES, I did wear my safety glasses - had to break the seals of that brown goop.
    The souls were NOT able to melt my glasses cuz I only buy really good safety glasses! :D:D:D)

    What's inside? Not much.... a magnetic core with a cardboard sleeve over it that
    goes inside what I would call a voice coil - inside the section with all the little holes.
    I can't make it visible in the photo, but there's a tiny voice coil inside that diameter
    that goes over the center magnet of the other half. The second photo you can
    sort of see the coil as a brownish ring around the aperture of the part with all
    the holes.

    CLEARLY a transducer... a "speaker" of sorts, without a cone. I cannot determine
    what the single conductor on the phenolic board connects to - it's not obvious.
    The 2 connections on the top go to the voice coil itself.

    So.... WHAT IS IT FOR? (well, WAS it for - it will surely never work again. Those
    screws took MAJOR EFFORT in a big vise with hammer and screwdriver to remove!!)

    I apologize to the Souls who were released.... small, harmless souls... souls of puppies perhaps?


    Attached Files:

  14. KL7AJ

    KL7AJ Ham Member QRZ Page

    This should give you a little insight into the operation.
  15. N2EY

    N2EY Ham Member QRZ Page

    I don't think so.

    The problem with that theory is that the frequency of operation is much higher than typical saturable reactors would be used. Low Q and all that.

    However, wobbulators were quite usable for sweep generators, and were commonly used.


    A wobbulator is a variable capacitor that is mechanically driven at high speed, to "wobble" or sweep the frequency of an oscillator. Motor drive is one method, but the most common I have seen is a device that somewhat resembles a dynamic speaker, complete with field magnet and "voice coil". But instead of a speaker cone, there's a disk (usually grounded) that serves as one plate of a capacitor. Another disk, spaced a fraction of an inch away, is insulated from ground and connects to the oscillator tank circuit.

    When the voice coil is driven by an AC signal, the moving disk moves closer and farther away from the fixed one, and so sweeps the oscillator frequency. By driving the voice coil with a sawtooth wave, a fairly linear sweep can be obtained.

    Note that the term "wobbulator" can refer to the component itself, the complete sweep oscillator, or, when capitalized, a particular brand name of sweep generator.

    73 de Jim, N2EY
  16. KJ4VTH

    KJ4VTH Subscriber QRZ Page

    >>I apologize to the Souls who were released.... small, harmless souls... souls of puppies perhaps?

    Oh, the HORROR!!!
  17. W7UUU

    W7UUU Premium Subscriber QRZ Page


  18. KL7AJ

    KL7AJ Ham Member QRZ Page

    Not so....look at the specs on the llnked Jerrold sweep generator. Besides, the oscillator doesn't have to be at the carrier is converted upwards.

  19. KL7AJ

    KL7AJ Ham Member QRZ Page

    However, in this case, it does look like a capacitive wobbulator. At the TV station I worked at we had a Marconi sweep generator with a saturable reactor...just like the Jerrold.

    Just show's there's more than one way to shave a goat!

  20. W7UUU

    W7UUU Premium Subscriber QRZ Page

    After dissecting the unit, and having NO IDEA what a "Wobbulator" is/was, your description seems to be 100%
    borne out by the facts inside this unit. It fits EXACTLY as far as I can tell. I do remember once as a kid reading
    in QST or some such about a "Wobbulator" - never had a clue what it is...

    Of course, it's dead now... on one hand I dislike I had to destroy it to figure out what it was, and
    on the other hand I'm glad I did so that at least I learned something. It's not like it had $$ value in
    this day and age, so I consider it on balance a positive learning experience.

    Thanks for the commentary.

    And sorry for the lost souls of the few little puppies that were inside... they meant no harm :)

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