[klondike98]

Some of you were interested in seeing this one tuber from the local museum. A few pictures first:
[Image: https://www.dropbox.com/s/rpmikemhihm32a....jpg?raw=1]
[Image: https://www.dropbox.com/s/cn1q3hp6s0qpp1....jpg?raw=1]
[Image: https://www.dropbox.com/s/tcysa07yxkzaam....jpg?raw=1]
[Image: https://www.dropbox.com/s/zwgmufskldxsbw....jpg?raw=1]

It uses a single #32 tube. It has 4 wires coming out the back and I can just see traces of color on some so I labeled them in the schematic. Here is the schematic if I've traced everything correctly:

[Image: https://www.dropbox.com/s/b27xj55y1p56dh....jpg?raw=1]

The movable tickler coil has continuity however the fixed coil is open. I also hear a slight scraping in the tuning capacitor as it goes through its rotation. I've labeled the chassis as ground. The rotor on the tuning cap is grounded. I'm in the process of searching through the many one tube schematics on line in hopes of finding a similar one. So far a few similar but none with a 32.

The case is cardboard with the pressed foil designs on the front, very neat I think. It will take some careful cleanup but should look a little better when clean.

[MrFixr55]

Hi Bob, this is a typical grid Leak detector with feedback, in other words, the Armstrong Regenerative receiver. The only differences are use oof a tetrode and a tuning capacitor as opposed to a variometer. Seems that the white wire is the antenna, black is ground, A- and B-, Red is +2V from a single lead acid cell and the final wire (pinkish?) is B+

My guess after reading the RC10 version of the RCA Receiving tube Manual is that B+ should be 45V. The manual states that plate voltage for a grid leak detector should be 135V through a 250KOhm resistor and a max screen of 45V. Since the screen, B+ lead and one pin of the phone jack are connected together and since by 1930 a 45V B battery existed, it is likely that the B Battery should be 45V. Grid leak should be a 2MOhm resistor and 250pF capacitor. The movable coil controls feedback. This is a simple radio, likely CA 1932 I wonder if it was a Words Airline and how much it sold for.

[Radioroslyn]

I can think of one set that does use a 32 tube and that is the National Radio SW-3 2VDC model. Although it's setup is pretty different from your set. As for the open coil. The rule of thumb is that feedback winding equals about 15-20% of the tank coil. If the tank coil on your set is for the bcb would be about  90t of small gauge magnet wire. The more turns the lower the frequency. Gauge is not all that critical but direction is as it should be wound the same as the feedback.

By experimenting with the grid leak values it can change the sensitivity, distortion, and selectivity.  Generally the resistor will change the gain (1-5megs but have seen 10megs used). The cap is some where betwixed 250mmfd-25mmfd.

It heard that the 1B4 is a less microphonic tube than the 32 when I was working on the SW-3.

Have fun w/it and they don't like strong signals.

[klondike98]

Thanks guys! Very helpful info.

[radiorich]

Hello Bob,
how cool is that I really like that Cabinet design someone went into a lot work on that !
Something like this set would be a fun project to build .

Sincerely Richard

[TV MAN]

Looks interesting Bob! I'll love to see how you do the cabinet. I wouldn't know what to do tho ... wheres all those leaky paper caps and firecrackers

[klondike98]

Yes the cabinet is going to be interesting. It’s more like a painting or paper restoration than a radio cabinet. Neither of which I’ve ever done before. I do like to watch videos of painting restorations and have seen some paper restoration on the Repair Shop.

[klondike98]

You guys inspired me to give the cabinet an inital go. I'm only part way through cleaning and it took a bit of work to get this far. I started by trying to get the silver paint off the area around the center knob hole along with a few other splatters. It looks to me like silver model paint but who really knows.
I used a technique I learned by watching Baumgartner Restoration videos for fine art restoration. He sometimes uses a scalpel to scrape off paint splatters. Its a very delicate scraping and picking to get the unwanted paint to flake off and is very slow going but in this case it did a decent job. Then I wanted to see if I could get the dirt and grime off the decorative sections. I started with 1) cotton swabs moistened with plain water, then 2) water with a little Dawn in it, followed by 3) straight Dawn with swab rubbing. I did get some dirt but much less than I was expecting. I gave some 4 zero steel wool a try with gentle rotation and that started to get things a little better but wasn't really doing much of a job. I finally moved to using some Brasso on a cotton swab and working in around the decorative section. This finally started to make some progress and what you see below is where I quit for the day. Here are the "before and "so far" pics:

[Image: https://www.dropbox.com/s/rpmikemhihm32a....jpg?raw=1]
[Image: https://www.dropbox.com/s/44icvm5iq3f03x....jpg?raw=1]

[Eliot Ness]

That's a very unique radio and I really like it. So far you are doing a great job Bob! Thanks for sharing!

[MrFixr55]

Love the art deco on the cabinet, you are making it pop. Interesting motif between the Native American and the coonskin capped explorer, the Conestoga Wagon (Studebaker?), the farm barn and silo, skyscrapers and the trimotor airplane, almost like a century of progress motif.

[radiorich]

Hello Bob,
Wow that really looks great my friend!
Sincerely Richard

[klondike98]

Made some progress on this unknown 1 tuber. I've restored the cardboard cabinet to a level that I think is acceptable (plus I've run out of further ideas).

[Image: https://www.dropbox.com/s/s31781bje8lgzm....jpg?raw=1]

I finished cleaning up the gold section, then started working on the areas where the fabric covering the cardboard had frayed, been torn, or was simply missing. Mostly that was in the corners and high spots where it would get worn. I used some Weldbond Universal Adhesive to consolidate the frayed fibers of the fabric so they would not continue to fray. For smaller areas it also served to fill in some of the missing fabric. If there was a larger gap, I used some Timbermate wood filler. After the adhesive and wood filler dried, I did the touch up painting. There was a small amount of gluing down some loose edges of the fabric and it was all followed by two coats of a furniture wax.

[Image: https://www.dropbox.com/s/7acar8fmv5hejg....jpg?raw=1]

The other thing I was able to do was take the fixed coil off the radio to get a better look at it. It turns out there are two separate coils on the fixed tube. One of the coils has what I think must be a missing connection. I was able to get measurements on both coils but the connection I've labelled #4 is just a little stub of a wire found in the center of the fixed tube. I don't know where it might have been connected (if at all). I've redrawn the schematic to reflect the new info along with a diagram and photo of the coil out of the radio. Hoping someone can make sense out of it....

[Image: https://www.dropbox.com/s/1hm07vr4c97udv....jpg?raw=1]
[Image: https://www.dropbox.com/s/cnciwtlb03k559....jpg?raw=1]
[Image: https://www.dropbox.com/s/1swlfz3usii839....jpg?raw=1]

[Chas]

Terminals 4 & 2 create an antenna input coil of which one end is earth ground the other antenna. That makes the entire coil assembly a three circuit tuner.
Option is given to ground the chassis or not to earth, depends if the ground is a counterpoise, useful when no earth is nearby such as 2nd or higher floor of a building.
Being a regenerative set such an antenna input option helps to prevent hand capacity effects. Might look about the cabinet for some sort of connection to earth via chassis or other to the front foil design.

[morzh]

Not sure I get the phones connection.

As for the hanging wire - by chance, it is not an Antenna input?

[MrFixr55]

For Phone connections, one pin jack connects to B+ and also to the screen. This supplies B+ to the headphone. The other pin connects the phone to the detector plate through the feedback coil. In other words, plate, feedback coil and phones are all in series and connected to B+.
I'm with Chaz on what the other connection to the antenna coil is, it's ground or to a counterpoise.