Merit Transformer Mystery

[KD1SH]

   At a small local hamfest this past Saturday, I came home with a couple of "mystery boxes" filled with assorted components and parts. It might seem odd, but I often deliberately hold off looking through the contents of boxes like that until I get home, because I enjoy kicking back in my recliner after the 'fest and exploring what's in there, with a couple of "save" containers nearby, as well as a "junk" container.
   Anyway, one of the boxes contained a very nice UTC S-19 modulation transformer, which will likely find a home in my next PW homebrew rig. Additionally, there was a similar-sized transformer: a Merit A-4022. With the "A" prefix and the fact that it shared a box with the S-19, I'm assuming that it's an audio transformer, although apparently some Merit television replacement transformers also carried the "A" prefix as well. I'm thinking that it's a "universal" modulation or driver transformer, given the eight terminals. I was only able to find three Merit catalogs on the web, dated 1951, 1960, and 1961, but unfortunately, none of them listed an A-4022.
   Has anyone ever come across one of these?

[W1NB]

ChatGPT indicates that the A4022-1 is a swinging choke filter reactor so it would seem logical that the A4022 is the companion modulation transformer, but it found no specific info on it.

Here is some specific info on the A4022-1:

The Merit Coil and Transformer Corp A4022-1 filter reactor, identified by NSN 5950-00-578-8729, is a specialized component used in various military and industrial applications. While specific product applications are not extensively documented, its technical specifications suggest its use in systems requiring inductive impedance at audio and power frequencies, typically up to 20 kHz.
wbparts.com

Key Specifications of the A4022-1 Filter Reactor
Inductance Rating: 200 millihenries
Operating Current: 1.0 ampere DC
Mounting Method: Threaded stud (32 threads per inch, 0.138 inches in diameter)
Terminal Type: 3-pin
Enclosure Type: Fully enclosed
Dimensions: Approximately 2.688 inches (length) ? 2.312 inches (width) ? 2.750 inches (height)
Part Number: A4022-1
National Stock Number (NSN): 5950-00-578-8729
These characteristics align with components used in military communications equipment, radar systems, and other electronics requiring stable inductance and current handling capabilities. However, without specific product documentation, pinpointing exact applications remains challenging.

[KD1SH]

Thanks; some good information there. I suppose I should get with the times and make use of some of those web-based AI's.
Since the A-4022-1 is a swinging choke, though, I'm doubtful that a modulation transformer might have been considered a "companion" piece, since a swinging choke is entirely a power-supply component. If it were a modulation-reactor type of choke, maybe, but I suspect that very few low-powered modulation lash-ups used a reactor.
When I have a chance, and my bench is cleared of current projects, I'm going to set to work mapping out that terminal arrangement and try to work out some of the ratios to get a better handle on this thing.

ChatGPT indicates that the A4022-1 is a swinging choke filter reactor so it would seem logical that the A4022 is the companion modulation transformer, but it found no specific info on it.

Here is some specific info on the A4022-1:

The Merit Coil and Transformer Corp A4022-1 filter reactor, identified by NSN 5950-00-578-8729, is a specialized component used in various military and industrial applications. While specific product applications are not extensively documented, its technical specifications suggest its use in systems requiring inductive impedance at audio and power frequencies, typically up to 20 kHz.
wbparts.com

Key Specifications of the A4022-1 Filter Reactor
Inductance Rating: 200 millihenries
Operating Current: 1.0 ampere DC
Mounting Method: Threaded stud (32 threads per inch, 0.138 inches in diameter)
Terminal Type: 3-pin
Enclosure Type: Fully enclosed
Dimensions: Approximately 2.688 inches (length) ? 2.312 inches (width) ? 2.750 inches (height)
Part Number: A4022-1
National Stock Number (NSN): 5950-00-578-8729
These characteristics align with components used in military communications equipment, radar systems, and other electronics requiring stable inductance and current handling capabilities. However, without specific product documentation, pinpointing exact applications remains challenging.

[N1BCG]

It certainly looks like an audio transformer although looks can be deceiving. I'd map out which terminals have continuity and check resistances to get a rough idea as to where the terminals connect to the windings.

After that, a 1 kHz tone can be used to further check the turns ratios by comparing the input and resulting output levels for the various windings. Next would be to sweep the frequencies to see what kind of response you get. Note that the higher impedance windings will likely need some amount of loading for a proper evaluation.

I prefer this gentle method over the brute force line cord test some ops advocate. The excitement from blown breakers and burnt windings wears off quickly.

[Opcom]

It has a whole lot of terminals for a choke.

[W2NBC]

The "Merit" section of this pdf lists the A-4022 :

https://www.worldradiohistory.com/Archive-Catalogs/Radios-Master/1949-14/Radios-Master-1949-N-Transfomers-Chokes.pdf

[KD1SH]

Excellent searching. Thank you!

The "Merit" section of this pdf lists the A-4022 :

https://www.worldradiohistory.com/Archive-Catalogs/Radios-Master/1949-14/Radios-Master-1949-N-Transfomers-Chokes.pdf

[N1BCG]

Driver transformer!

Further proof that nothing evades the unblinking eye.

For the impatient, it's on page N-73 (pdf page 75 of 86).

[KD1SH]

  The truth is out there, but sometimes it takes some persistent digging. Thanks again to W2NBC.
I was figuring that it would be a driver transformer, since its small size and weight would make for a very small modulation transformer. An interesting driver transformer, since according to the datasheet, it can be used for a single-ended driver to either a single grid or push-pull modulator grids.
It's a shame that in many cases, the original instruction/connection documents for transformers like this have been lost to history, but there are workarounds for that.

Driver transformer!

Further proof that nothing evades the unblinking eye.

For the impatient, it's on page N-73 (pdf page 75 of 86).