[MrFixr55]

Chip, congrats for getting back into the hobby. I am heading toward 69, retired last year and do this (and other things) to keep my mind going. Keep doing the same!

[MrFixr55]

More ramblings:

Although I live in a suburb of NYC (Huntington area of Long Island, population nearly 200,000), somehow, I had always been interested in how rural people lived. This has translated to Farm Radios, of which i have several, of various eras.

The first radios were battery powered so there was not much of a difference as to whether you had a farm or lived in the city; Town or Country, you got the same radios (for the most part). Line powered radios (referred to as "socket power") appeared between 1925 and 1928. For the farmer, the radio was more of a tool, for weather and crop reports, than a source of entertainment other than church services and some "Saturday night" listening, due to the expense of batteries and inconvenience of charging the "A" battery (see below). The US Dep't of Commerce published pamphlets on how to build crystal and 1 tube radio sets.

Obviously, due to population density, electrical service was first brought to the cities. The first service was 110 VDC in NYC and other areas. The advent of AC (Google "Current Wars, AC vs DC), high voltage transmission, hydroelectric power, etc., power came to the suburbs. Due to the cost of copper and labor, it took many years (even into the 1950s or later) for electrical service to arrive to rural farm areas, and it took rural farm cooperatives and the Roosevelt era TVA (Tennessee Valley Authority) to get the job done.

Until then, the farmer had only a few choices to power the farm radio:
6Volts DC- Farm Radios were developed using similar techniques as the car radios that started to appear in the early 1930s (Tubes with 6V filaments and a vibrator power supply for the "B" voltage). These radios either used the same circuits or used certain similar tubes as ordinary 6V tubes but with less filament current, or by placing 2volt filament tubes in series. This was done because some farms were not mechanized, and the farmer would have to bring the battery to town to have a gas station charge it. The "Win-Charger" was a popular accessory on some farms, as it provided power to charge the battery which was also used for lighting. In the late 1930s, after the formation of the TVA and rural electrical cooperatives, some companies, such as Zenith, made radios that could be switched from 6V battery to 115VAC with the flip of a switch.

30VDC sets. Some larger farms would have a Delco (General Motors) 30vDC electrical generator, which would be used to charge a bank of lead acid batteries. This system would provide greater amounts of lighting to a house than the 6V system, therefore it made sense to design a 30V radio. These sets used "space charge" tubes that did not require high plate voltages.

A later development was the 2V lead acid battery (1/3 of a 6V Car battery) or 2.5V "Air Cell" battery and 90 or 135V "B" Battery sets. These were for the non-mechanized farm. The farmer would take the "A" (filament) battery to be charged, and purchace replacement "B" batteries which were sold in 45V blocks.

When Sylvania came out with the 1A7, 1N5, 1H5 and 1A5 tubes, in 1938, that could run on 1.5V A batteries and 90V B batteries, portable radios became available and rather popular. It seemed reasonable to build farm sets using the exact same circuits or even the same chassis that the portables used.

When power came to the rural area, the farm radio became obsolete. Some were kept going by purchasing a socket power unit from the manufacturer or from Sears. Others were discarded.

BTW, I don't know if I would remove the plate with the engraved message from the top of your radio. The fact that the radio was "personalized" is part of its story and may also add value.

[David]

Living in the power outage state (Florida) Farm sets were around until transistors came alone. I know a number of people who have sets that have been in the family a long time. Myself I do like a good outage gets rid of all the line noise. Plus I can play with the generator. Were are looking at 40-50 MPH winds tomorrow will be using a farm set powered by a solar generator and a 1.5 volt battery. The B battery is 90 volts have a converter as shown on Phils old radios.  https://antiqueradio.org/bsupply.htm

[Radioroslyn]

That transformerless design is a little dangerous with the line connected to the B-. If the ant terminal ever came in contact with ground it's bye bye antenna coil poof gone in a flash.  You may want to consider something like this:

   

It allows adjustable A voltage from 1.5v to abt 6v @ 1.5A.

[7chip7]

I have have another audio transformer from another battery set (a 1950 Zenih) and I am wondering if it can be used to replace my toasted transformer. See attached photo. the primary DC resistence is 727 ohms and the secondart is .6 ohms.

[David]

The solar generator has no ground.

[RodB]

You should compare the 3V4 plate load impedance to the one in your radio. If it's close then it should work well.

[Radioroslyn]

Chip,

How you solve the mystery is to ignore the dc resistance of the opt. Lookup the plate load resistance of the tubes that you are comparing. Since that set had a 1Q5 you're looking for something around 8K.

[Arran]

There is also the 1T5G/GT which has similar specs to the 1A5G/GT https://frank.pocnet.net/sheets/127/1/1T5GT.pdf except for the fact that the plate load resistance is only 14,000 rather then 25,000 Ohms, and the 1T5 is a beam power tube. 
Regards
Arran

[7chip7]

I looked up the load resistance for the 3v4 and it is 10k
I looked up the load resistance of my 1q5 and it is 9k
So I do think I will use the audio transformer from the 3v4, it should work.
Audio transformer data such as impedance and inductance has always been my weaker part of electronics. I tend to be a little lazy on the subject and depended upon do and try my way out. So now I know a little more about tube specs, you folks are very helpful, and this old mad thanks you.
Chip

[7chip7]

I am now looking over the power supply section of the schematic. I labeled the Voltage line of the B and A battery's.  Looking at the B- line on the schematic (marked with a red arrow), is that the only place the B genitive goes?  See attached

[Radioroslyn]

A= filament voltage B= plate voltage.
so yes.

[7chip7]

Finished my research on this 40-95, I have all new caps and resistors, going into the wiring now , going to start on the audio end and test each stage as I go. I already started to build a battery eliminator a few weeks ago, so I will finish that too. Thank you guys for all your help.
Best regards
Chip

[Arran]

A point of order, there were 32 volt DC powered sets, but I'm not aware of any 30 volt ones. You may ask why 32 volts was chosen, well apparently 32 volts DC was the standard for electric lights, and fans, on trains at one time, it was also easy to hook up four 8 volt lead acid storage batteries in series to be charged by a farm generating plant. I have a Canadian made Phonola, built by Dominion Electrohome, and apparently based on a Wells Gardner design as it does not use a #48 pentode power output tube, it uses a 6A6 driven by a #43. Other then the #43  the the other tubes are all 6.3 volt AC types in a series-parallel arrangement to add up to 32 volts. Unfortunately someone plugged the set into a 120 volt outlet, fortunately they are all common and relatively inexpensive tubes, and two actually survived this mishap, nothing else was damaged. Suffice it to say it will never have anything resembling an AC line cord with a NEMA 15 plug again. 
Regards
Arran

[7chip7]

Yes, and the change over from DC to AC way back when, must have created all kinds of problems I think the AC at first was 25 cycle not 60 cycle like today. I also read somewhere once that at first only one side of the streets were converted to AC the other was still DC, so the radio repair man must have had a time with all that.
Regards
Chip