[PeterN]

I was wondering if anyone knows if these AC/DC transformer-less sets were actually used on 110v DC anywhere, and when.

I read that the model 40 (1929) was actually made for 110v DC only. I expect that consumers in the "eastern seaboard" states, that were using the Edison System (New York) during the early days of electrification (1890's), would be likely 110v DC users, but that would have been long before radio really caught on, when most power distribution systems had been "standardized" on 110/220 AC. The "All American Five" transformer-less sets didn't really make a prolific appearance until after WWII when everyone was using 110v AC.

I find it interesting that the "transformer-less" sets mention AC or DC operation in their operator/service manuals and go so far as to mention that when running on 110v DC, if no sound is heard, reverse the plug.

I have searched the Internet without success, looking for any history that tells when and where 110V DC was used in the home, after the radio era began. 

Thanks in advance.

[morzh]

http://www.nostalgiaair.org/PagesByModel...040180.pdf


Model 40 does not have a rectifier, so it would be a DC only model.
This however does not say anything about using AC/Dc sets on DC. Which is perfectly fine.

[jrblasde]

Good evening, folks. Power station engineer here!

The east coast had pockets of DC-only power well into the twentieth century. I’m wanting to say it ran into the 1950’s, but certainly was common through the 40s. In fact, there’s still DC power transmission in various parts of the country. It’s just not distributed for use as DC.

[PeterN]

Joseph,

Thank you for the confirmation. I knew that there must be more to the Transformer-less AC/DC radios than the radio design engineers realizing "hey, we saved the cost of the power transformer, and by the way, you could also use it on 110v DC if you had any". I didn't know that anyone had any (I was born in 1956).

I know some of the later farm radios were designed to run on 32v "farm power" (local generators/windmills) that was being used for lighting in the barns, before the "rural electrification" movement started distributing standard power.

[jrblasde]

You’re welcome! I was born in 1995, so this is all second-hand information to me from the industry. I did some research this morning to prove it, and it looks like DC service continued in much of the east coast into the 1960’s, simply for legacy elevator, motor, and metro operations in larger cities. However, I read that Manhattan’s electric company offered DC as an option to residents up until 2006!

    But you are right. From what I’ve read, the appeal of the AC/DC design was two-fold. First, make a device that can be used by the largest group of consumers. Second, make it cheaper and more folks will buy it. I’m actually restoring a 46-480 right now, and it is AC only. I was looking at the specifications for the transformer, and I notice in the 1949 parts catalog that the selling price was $9.50. That would have been considerable for that time (my granddad had his first job out of college in 1966, and has told the story of getting a “generous” per diem of $6 per day when he traveled for the first time). I’ve also got a 49-906 set which is AC/DC. Just my opinion, but I feel that the audio quality doesn’t suffer at all from the cheaper circuitry.

    American engineers took a lot of pride in the AC/DC design. It has a likeness to the spirit of the Ford Model T (assembly line production and black paint will hold the price down) and the Volkswagen (I’m thinking more in terms of the literal translation of the “people’s car”; let’s sidetrack the nasty history and politics of it), except it made the radio become affordable to the average person. Particularly after vacuum tube technology caught up to the point when the filaments could drop 110-120 volts without a ballast. Then it became even more affordable!

[MrFixr55]

Some of the original Edison DC generators were in use until the 1940s. The NYC subway and electrified Long Island Rail Road branches still run on 600VDC. The NY Central (Metro North) and Amtrak run on 2.5KV AC I believe. The Waldorf Astroria lighting circuits were DC until a major renovation in the 1970s. It is interesting that (I believe) that some of the first "AC-DC" sets were more expensive than transformer powered sets. Obviously, with a heater string that could drop 15-120V without resistors increased reliability, and lowered cost. Sound output power and sensitivity both suffered in the "AA5" AC-DC Set when compared to transformer powered units.

The universality of the induction motor in consumer refrigerators (See GE "Monior Top" refrigerator) starting in the 19 teens and 1920s and the need to efficiently transmit power generated by hydroelectric dams almost required the conversion of power systems from DC to AC. Granted, toasters, light bulbs and most small appliances that used brush type motors could use either DC or AC. Load balancing of DC generation systems was difficult at best. The 2 major electric manufacturers were Westinghouse and Edison General Electric. Google "The Current Wars" for the full story. Nicolai Tesla, the inventor of the induction motor worked for Edison. When Edison reneged on a promised bonus, Tesla went to work for Westinghouse and helped develop the AC power transmission system as well as practical induction motors. Edison claimed that AC was more unsafe than DC and even electrocuted animals, including a rogue circus elephant, with Westinghouse alternators. These demonstrations caused New York to be the first state to use electrocution using AC as a humane (???!!!) way of executing condemned criminals. Westinghouse won the contract for the Niagra Falls Hydroelectric plant and the "Current Wars". Not the dropping of the name Edison from General Electric.

DC outlets and line cords were not "polarized" therefore the plug could be inserted so that the plate of the rectifier was connected to the negative pole, therefore not being able to pass current to the B supply. The tube heaters would light, but there would be no B+, therefore no sound.

Several late 1940s or early 1950s Philcos used a full wave voltage doubler rectifier, especially in their radio - phono combinations. The use of the voltage doubler limited the set to AC operation, even though there was no power transformer. However, this was not really an issue because the phono motor required AC. The level of performance for these sets was very near the performance of a 5 tube transformer powered set, especially when they used an 8" speaker.

[jrblasde]

Fantastic report, Mr. Fixr! I had never read about AC/DC sets originally running at a higher price than AC-only models, though I do believe it. It would have been cutting edge technology at the time, and the higher thermal burden on the filaments would absolutely call for a more robust tube. I guess the original appeal of the AC/DC set would have had to have been mass production of a singular design for all.

Just comes to show, no one person is an expert on anything!