[MrFixr55]

Glyphmon, if cheap enough, I say go for it! BTW, I have the AM only version of the R28. It is an interesting set to say the least, a "transitional" set with an RF amp, pentagrid convertor , no IF amp, a biased detector and new tech 2A5 output tube which replaced the '47. Eventually, the power detector was replaced with a Diode / triode detector / 1st AF amp, the RF tube disappeared, an IF tube was added and Voila, the standardized 5 tube "AA5" circuit (transformer powered version). It was RCA's loss leader for the year until Philco came out with the 80 Jr and undersold them by $10.00 and started a price war.

Although I have spent my whole life in Suburbia, I have always had an interest in Rural America, especially in the latter part of my career where I provided phone support and occasionally on-site support to rural Hospital Laboratory customers. Rural America faced many different problems than urban and suburban America, especially during the Great Depression, dust bowl and WWII. "Intellectuals" disparaged rural folk as "hayseeds", but these people dug the coal mines, drilled the oil wells and raised the crops and meat that fed us, and we would not have been a country without them. I'm not sure how many Ivy League college "Poly-Sci" (Political Science) graduates could feed themselves and others. Farm Sets have a lot of history in them and were an example of the issues faced in delivering entertainment and news to very hard-working people who did not have electricity and possibly did not even have mechanization. This set is an example as it was designed to be powered by disposable primary batteries as opposed to a storage battery. The set was likely listened to very sparingly, for news, religious programming if travel to church was difficult and very occasional entertainment. The fact that it was powered by disposable batteries is a possible reason for the low power output.

I would not think of these sets as being "cheap"; look at the strength of the cabinet. The big restriction in these sets was not in sensitivity, it was in audio power output. This one has an output of about 200 mW, about the output of a shirt pocket transistor radio from the 1950s-m1960s, but slightly better sound from the 8" speaker. However, this set may have replaced the farmer's 10 or 15 year old Atwater Kent Model 20, Freshman, Crosley or other 3 dial TRF set that had an output of less than 100mW (more like 10-30 mW).

I am not sure who made this set; Sears had many suppliers including Arvin and Detrola.

Sears used this series-parallel arrangement on many Silvertone Farm radios of this era that used 2V tubes. Others had the filaments in parallel but had a rheostat to set the filament voltage depending on whether using 3V fry calls, 2.5V Eveready Air Cell or 2V storage cell.

The filaments of the set would run for about 30 hours on good alkaline D cells, but 4.5 Volt wall wart power supplies are not hard to find. Building a 90V power supply is not hard to do. We probably should have a permanent thread on that; it was recently discussed. I will copy paste a link to the last thread on the subject; it was thorough.

Re "Resto-mod, or Wreck-o-vation, I would not recommend the gutting of the radio chassis. The chassis is relatively easy to convert to utility power by building the appropriate power supply. Any 8" speaker will work, but a high compliance one would be best. Your biggest issue will be the output transformer. The 1E7 tube is generally run at 135V, in push-pull through an output transformer having a plate to plate impedance of about 24,000 Ohms. I think if you can find one at around 12KOhms, you will be OK. Alternatively, you could install an aux output jack and use the radio as a "tuner" to drive a hidden "Middle Kingdom" mini amp. Just make sure that any mod could be easily undone. For example, If you want to add a stereo amp and speakers, make a new baffle board and remove but preserve the original. The baffle board can support the stereo speakers and amp but also hold a speaker for the original chassis so it can be demonstrated.

Because these tubes are Series-Parallel, you want to check the filaments with a VOM or DVM. The filament pins are 2 and 7 in all of these tubes.

The tubes picked and stages are rather strange. The set has no RF amp, and a typical convertor and IF, and there is where it ends. Instead of a combination detector / 1st AF amp, the set uses a 1H4 triode as a diode for a detector, another 1H 4 triode as a 1st AF amp, the triode section of a 1H6 Duo Diode triode as a 2nd AF amp, then the 1F7 with the 2 pentode sections paralleled as the output. I don't understand the engineering reason for this. It was common to "inflate" tube count, but in a battery set, this is not a good idea. They could have used the 1H6 as the detector / AFC / 1st AF, the 1H4 as a phase invertor and the 1E7 as a push pull output and saved a tube.

If you buy this set, keep us posted. We are happy to help you get it working!