[MrFixr55]

Edited 05/21/23) I believe that this radio was aftermarket, therefore found in many cars such as the Ford Model A and its competitors. It did not come with a power supply. It was a TRF unit that used 3 24As as RF Amps, a 71A (???!!!) as a detector, connected as a diode using the cathode and grid. The plate was grounded and acted as a shield. A 01A served as the AF Amp and a 71A served as the output. The 24A filaments (2.5V) were in series. There were dropping resistors for the 2 71As and type 01A. The tube filaments ("A" Supply) ran off the car's 6V battery / generator. For this and other early auto radios, the B supply was from four 45V B Batteries in series. There was no C battery, there was a dropping resistor in the negative circuit to get the C-. To get B+ without using batteries, a motor generator or "Dynamotor" was used, or one could buy a Mallory vibrator power supply.

This radio was circa 1930-31. A 71A put out a whopping 0.7W of audio. I can't imagine the filaments of the 71As and 01A in this radio lasting a real long time. The '33 and later Ford Model B V8 had a factory radio available that was built by Grigsby- Grunow (Majestic). It used 39s for RF and IF Amps a 38 (???!!) as an autodyne mixer, 38s in Push Pull for Power Amp and an 85 Detector AVC and 1st Audio, and a dynamotor for the B supply. In 3-4 short years, Auto Radios substantially developed into circuits very similar to home radios, with built in B supplies, either by "synchronous vibrator" or by a much simpler vibrator and rectifier. A lot of this credit goes to Philco (and Sylvania their tube supplier?), and possibly RCA (or not, but they just took credit?) for developing the 42, the first power pentode with heater / cathode instead of a filament cathode (developed before RCA's 2A5, the replacement for the '47), and some other 6V tubes such as the 77 (replacing the 2V 57), the 78 (replacing the 58), the 6A7 (replacing the 2A7), etc. Other 6V power Amp tubes such as the 38 and 41 followed(I am not sure when the 6A4 / LA was introduced or by who. Philco was also an early pioneer for using 6V tubes in their home radios, before RCA, Zenith and others switched from the 2.5V versions, even switching from the 80 to the 84 rectifier with a 6V heater and tubular cathode, thereby eliminating a winding on the power transformer.

In just a few short years (1933-1934), Philco introduced the Transitone 10, a thoroughly modern 6 tube circuit with 44 remote cutoff (super-control) pentode RF, 2A7 pentagrid Converter, 44 IF, 75 Detector / AVC, 1st AF Amp, and single 42 Output. Power Supply was by asynchronous vibrator and 84 full wave rectifier. Other than Push Pull Output (and not all newer radios had push-pull), reactance pushbutton tuning, signal seeking and newer style tubes, this radio had everything that a tube type car radio had, all the way to the the introduction of all transistor radios in 1958-1963.

If you are interested, search Nostalgia Air for Ford and Cadillac radios for interesting circuits and the evolution of Car Radio. I wonder if anyone did a comparative chronology of car radios showing the evolution from the Transitone 3, through Superhets, through In Dash, inductance tuned, push button, "transistor powered" w/ space charge tubes to all transistor to the high tech radios of current production. Have to include the Chrysler "Highway HiFi" record player, Lear Jet tape players, 8 tracks and cassettes.

I think that this is a seminal radio and historically important. If I had a Ford Model A, I would have this in it!