The Farnsworth Television and Radio BT-58 Radio ProjectThis is the story of a rare Farnsworth radio that a friend and I collaborated on to bring back to life. It started life as a portable radio that could be operated off an internal battery pack or by plugging it into the AC line and in that regard, it is similar to my 1942 Philco portable radio (written about elsewhere on my website). This radio is special because it was made by the Farnsworth Radio and Television Company around 1942 just before the government stopped all commercial radio manufacturing and sales.
A comprehensive story containing historical, educational, technical and biographical elements & opinions
A very rare picture of a surviving Farnsworth BT-58 portable radio
showing what they actually looked like.
image used by permission
Before continuing, I'd like to say something about the man who owned the company that made this radio, Philo Farnsworth. He is the forgotten inventor of electronic television and many other brilliant inventions that are beyond the scope of this little story. Farnsworth's life is well worth looking into for the lessons it teaches about how technical brilliance and genius is not enough to be a success in the world of American Business. Indeed, geniuses like Farnsworth and Armstrong are universally exploited by ruthless business people who's only talents are their ability to manipulate the legal and financial systems and in their ambition to wealth, they think nothing of ruining the very people who make their wealth and business success possible.
Unlike the Troy Radio and Television Company (one of their radios I also write about on this website), the Farnsworth Television and Radio Company survived long enough to actually produce television sets during the early 1950s, but they didn't last very long once the big corporations dominated the industry. It came as a bit of a surprise to me to learn that people were watching television sets as early as the mid-1930s and indeed the 1936 Berlin Olympics were broadcast on German TV. In those early days, the so-called NTSC standard had not been formulated and Armstrong's FM system was not used to carry the sound. The sound for the early TV sets was carried on ordinary AM radio so that a viewer needed to have a TV set for watching the picture and a AM radio - like this one - for listening to the sound. It wasn't until after World War Two that FM sound was put on to the television signal and TV sets had their own audio receiver. This then is the story of a radio that was made by a television company founded by a brilliant television pioneer and a radio that could be used on a picnic (with its batteries) or at home on AC current. It could be used to listen to all the wonderful entertainment, music and news of its era or it could be used to produce the sound of some of the very first television programs.
My Farnsworth radioFor as brilliant as Philo Farnsworth was and as advanced and innovative as his work in electronics was, this particular radio is of a very conventional design and there is absolutely nothing innovative about it. Basically it uses the very same design features as the radios of the early 1930s, but it was and is a nice radio that works as well as any in its class. I have no idea how many of these radios were made, but probably very few as there are no pictures of this model or anything like it anywhere on the Internet.
By the way, there are a couple of things that are slightly unusual about how this radio was constructed. All the resistors are an unusual wire wound type instead of the much cheaper carbon type and all the parts that are bolted and screwed on have inspection stripes indicating a level of quality control usually only found on military equipment. Perhaps the factory had earlier had a quality control problem and so the managers brought in QC inspectors to make sure the products were of the highest quality construction, but that is just a speculation.
This then is the story of how I got my Farnsworth Model BT-58 radio and how I restored it.
How the radio looks today. The case is not original, but made out of a wooden speaker cabinet that fits the chassis perfectly as if it were made for it. The front panel is stained wood with period knobs. The big 'F' that makes the opening of the speaker was cut out by me in honor of Philo Farnsworth, the forgotten genius.
The front view of the BT-58 chassis. Note the heavily damaged speaker that I rebuilt.
The rear of the BT-58 chassis showing the old fashioned tubes with their grid caps. The unterminated wires in the center would go to a 1.5 volt 'A' battery and a 90 volt 'B' battery if they were plugged in otherwise it operates on 120 volts AC.
Lacking any official nameplates and identification, I penciled in the make and model and my own name on
the back of the chassis.
The radio when I first acquired itThis radio project began with a bare chassis and no outer case. The dial pointer (the red object below) and the loop antenna (making up the input RF tuned circuit) were also missing. The chassis was owned for decades by my friend David Dodd, but the outer case was lost so long ago nobody now remembers what happened to it or even what it looked like. To make matters complicated, there were no brand names or any other identifying marks on the chassis or any sub-assembly and I had no idea who made it or where to start to look for a schematic diagram. I did notice that the front dial was very unusual and I'd never seen anything quite like it. It was the dial that I used as a clue to track down the maker of the radio.
An unusual looking tuning dial.
Isn't that a really good looking red pointer?
Identifying the maker and the model of the radioThanks to the wonders of the Internet, I was able to look over dozens and dozens of pictures of old radios dating back to about when I guessed this radio must have been made (1938-1948). On a German antique radio site I found a radio with an identical dial and it was identified as a Farnsworth Television and Radio Company, BT-68 radio. I was very pleased with my discovery and then went to another really fantastic site to download the schematic. The first thing I noticed was that the schematic was very similar to the wiring of my radio and it used the same tube set, indicating that it was indeed a Farnsworth radio, but it was not exactly the same because it called for an extra RF amplifier tube that my chassis didn't have. That got me searching more and I found reference to a 1942 Farnsworth BT-58 radio, but because it was probably a very rare radio, there were no pictures of it - anywhere - and that is probably because there are none that have survived to this day. When I downloaded the schematic diagram and carefully looked it over, bingo, I had my radio exactly and right down to the last wire. I indeed had a model BT-58 Farnsworth radio.
Redrawn and usable schematic of my radio
Thanks to the Internet, the schematic of even this very rare Farnsworth BT-58 radio is available.
The original image I captured was hard to read and follow (especially the switching between battery and AC operation),
so I completely redrew the schematic on my PC by using the Paint program and now I have a superior schematic.
Restoring the old radio to operationExcept for the dial pointer, the loop antenna and the outer case, the radio was all there, however, the old beeswax covered paper capacitors were in very bad condition and naturally they and the electrolytic capacitors would have to be replaced. Modern replacement parts are available locally and are pretty cheap, so I began to take all the capacitors out and replace them with modern disk ceramic and miniature electrolytic versions. With the help of my revised and readable schematic, this took a couple of hours, but it was a rather simple task. I also had to replace some of the original wiring as the rubber insulation had fallen apart and that took some time too. I think I spent all of about $15 on this radio.
While I was at it, I traced down all the wires going to the 'A' and 'B' batterys and discovered that whoever had labeled them a long time ago had things all wrong. If anybody would have connected up a 7.5 volt battery to the 'A' battery (instead of a 1.5 volt battery), they would have instantly burned out all the tube filaments and destroyed the radio. As luck would have it, nobody had ever done that and all the tubes still work perfectly. Going through the radio and the schematic wire by wire I discovered a few mistakes somebody had made when they drew up the original diagram, but they were easy to find and correct.
There were two things that I was afraid might be show-stoppers with regard to getting this radio restored. First was the missing dial pointer. I didn't know where I'd be able to get another one of those, but then it dawned on me that I could make one myself. I took a strip of broken hacksaw blade and I heated it to red hot on my stove and then let it cool slowly to anneal it. Doing so made the steel very easy to shape so the top of it would fit in its guide and very easy to file the bottom of it into a pointer shape. I was really pleased how nicely the metal bent into the complex shape I needed and easily it was to file the metal away to form a pointer. After I had the steel pointer formed and shaped, I painted the thing with red fingernail paint to match the original red dial pointers I had seen in pictures. I installed the pointer and once in, I was pleased at how good it looked and how smoothly it worked as I rotated the tuning control.
The more serious looking problem was the heavily damaged speaker. About a quarter of the speaker cone was missing and the rest of it was torn and cracked. The speaker frame formed an important part of the structure of the radio and supported the tuning deck and the on/off/volume control so I couldn't just remove it and replace it with a modern speaker. I considered taking the "guts" out of the speaker frame and putting a smaller and thinner speaker in, but thought I'd wait and try an experiment first.
After I had all the new parts in the radio and after I had carefully checked all the wiring against the schematic diagram, I plugged in the power cord and turned on the radio. After a long warm-up, characteristic of tube radios, the radio came to life. I felt some surprise that all the old tubes still worked after being silent for over 50 years. What really surprised me was the good sound that came out, loud and clear, from the heavily damaged speaker. This was really unexpected because over a quarter of the speaker was gone and I expected it to rattle and be highly distorted.
Rather than replace the existing speaker with a smaller one, I decided to try to rebuild the speaker cone. First, I doped up all the cracks and tears in the speaker until I had the remaining 3/4s of it looking good. It occurred to me that I could replace the missing portion of the speaker if I would build it up out of multiple strips of tissue paper impregnated with a doping material. For a suitable light tissue I used, of all things, long, narrow strips of single layer toilet paper and for dope I used clear fingernail polish since I figured it would be tough and long lasting. I started by gluing down a strip, then I'd impregnate it with dope, lay down another strip, dope it, another strip, dope it and pretty soon I had the missing portion of the speaker cone completely rebuilt with a light, but rigid material that I hoped would match the characteristics of the rest of the speaker cone. After the dope had hardened and everything looked good, I turned on the radio. I was absurdly pleased with my little self because the rebuilt speaker sounded just great with no rattle or distortion and plenty of volume coming out of it. This was one time when one of my crack-pot ideas actually worked and worked well.
Rebuilt speaker after filling in with
doped toilet paper strips.
Placing it in a period style cabinet and final assemblyIn the meantime, my friend David took some old speakers out of an old cabinet, cut out a blank sheet of plywood for a front panel and gave me the pieces. I took the blank panel and cut out an opening for the dial and the control knobs and then carved an 'F' (for Farnsworth) into the opening for the speaker. I rather doubt that the original radio looked like this, but I have done my best to recreate something period. I have no idea what the original cabinet for this radio really looked like because this model is so rare that no pictures are to be found on the Internet.
Another critical part that was missing was the original tuned loop antenna. I bought some nylon standoffs and mounted them on the back panel to wind the coil on and then calculated about how many turns I'd need to tune in the broadcast band. I wound the coil with number 30 wire and then proceeded to fine tune the circuit. I found that I had placed way too many turns on the form, but I finally removed enough winding that the radio's "front end" was tuned in properly and now I can listen to KGO up in San Francisco (250 miles away) an night loud and clear on this radio.
From a historical stand point, I am glad I own this radio and it is kind of fun to think that perhaps I own the only surviving example of this model radio in the known universe, but gee whiz, what am I going to do with another AM radio, even one that can be operated portable on its own batteries? Right now I have it in the the nicest bedroom of my house that I use as a guest room on an antique "secretary's desk" and it really looks nice there and really adds to the decor of the bedroom.
This just added.
As of yesterday (May 31st, 2012), I became aware of the existence of another BT-58 radio (see picture at the beginning of this story). To the best of my knowledge, this is the only complete radio of this model number in existence and it would be wonderful if the radio could be fully restored and put back in working condition.
You know, when we think of World War Two, we usually think of battles and other military operations. In fact, life in the United States went on and people at home lived their lives as best they could and tried to be as happy as they could be. Having a portable radio and taking it with them to picnics, to the beach or to parties added to the pleasure people felt while doing such things. The batteries were very expensive and they didn't last very long and they were probably very difficult to get while the war was on, but the expense of owning and operating a wonderful little device like this was well worth it because of the entertainment and pleasant ambiance they provided.
There are a lot of historically important artifacts dating from the World War Two era, but most of them are of a military nature. Military artifacts remind the collector of how the war was executed, but I think we should remember that there was also a vitally important "home front" during the war too. In my mind, portable radios such as this one are precious artifacts that should remind us of the very important civilian side of the war. I sincerely believe that these radios are a very poignant snapshot into the lives of the parents, wives, sisters and younger brothers who had to endure the war while their sons, husbands and brothers, the soldiers and sailors, were away fighting, suffering and being killed. I think these kinds of artifacts tangibly remind us of everyday civilian life and make us realize that while the soldiers and sailors were enduring what they were forced to endure, they were also looking forward to the time when they too could return to the pleasures of home. Going on picnics on Sunday or to the beach and taking a portable radio with them so they could listen to ball games and popular music was certainly part of the "good life" they were looking forward to.
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If you have an antique AM radio and you need something decent to listen to, perhaps you should buy or build your own
Low Power AM transmitter
If you liked this story, perhaps you would like to read about another portable radio from this era
My Summer for '42 Philco portable radio
Or perhaps you'd like to read about my rare
Troy Radio and Television Company Art Deco radio
I have several other articles on old radios including a beautiful Fairbanks Morse that you might be interested in