Like most of my radios I acquired this Arborphone 25 from Ebay and it looked to be in very good condition. This radio was listed as an Arborphone “Grand”. I have been unable to find any historical record about an Arborphone Grand but this radio and radios that others call Arborphone Grand looks exactly like the Arborphone 25. My Arborphone 25 radio was damaged when it was shipped. There was no packing. My money was refunded and I set the radio aside for a year.
Eventually I decided to restore the Arborphone 25 radio first by getting it to play. Didn’t have a schematic but like most TRF battery radios from the 20s it is not difficult to trouble shoot without a schematic. The chassis consists of two sections. The AF section plugs into the RF section prior to screwing the sections to the base. I checked the continuity of the coils in the RF section and found everything to be good. The two tube AF section was a mess however. The battery multi-cable had seven conductors in it and almost all of the insulation was gone. It was essentially seven bare wires with bits of insulation here and there. I was able to determine the color of insulation for each wire. I replaced the multi-cable with an 8 conductor authentic looking cable I bought from Radio Daze. I pulled out the white conductor. The remaining seven conductors matched the colors of the original cable.
| Power Cable Conductor | Voltage | Function |
| Red | 6 Volts | A+ |
| Green | Common for A, B, & C | A-, B- C- |
| Brown | 135 Volts | B+ for Output Tube Plate |
| Blue | 90 Volts | B+ Plate |
| Orange | 22.5 Volts | B+ Detector Plate |
| Black | -4.5 Volts | C- |
| Yellow | -9 (UX-112) / -22.5 (171) Volts | C- |
There are three transformers in the AF section. The output transformer checked out good. The transformer coupling the detector to the first AF amplifier was replaced a long time ago and was a hack job but it still functioned. The transformer coupling the two stages had an open. As a temporary solution for the defective transformer I coupled the two amplifier stages with a capacitor and resistor. Someday I hope to find a suitable replacement transformer.
Next I drew up a schematic for the AF section to determine the function of the seven conductors in the multi-cable. Then I had to determine what to use for tubes. The tubes that came with the set were obviously not correct. There were three 226 tubes and 3 280 rectifier tubes, none of which would be found in a battery radio. I looked at dozens of battery radio schematics from the late 20s and found a six tube radio that used 01As and a 112 as the final output tube. I had the 01As and I found a 112 from some tube warehouse. Later I found that these were indeed the tubes used for this radio. Also the 112 could be substituted with a 171. Once I had the tube line up, I was able to determine the voltages with which to power the radio by studying tube data sheets.
Next I drew up a schematic for the AF section to determine the function of the seven conductors in the multi-cable. Then I had to determine what to use for tubes. The tubes that came with the set were obviously not correct. There were three 226 tubes and 3 280 rectifier tubes, none of which would be found in a battery radio. I looked at dozens of battery radio schematics from the late 20s and found a six tube radio that used 01As and a 112 as the final output tube. I had the 01As and I found a 112 from some tube warehouse. Later I found that these were indeed the tubes used for this radio. Also the 112 could be substituted with a 171. Once I had the tube line up, I was able to determine the voltages with which to power the radio by studying tube data sheets.
The four output jacks are located in the rear AF section on the left side when looking from the top towards the rear. When driving the output through the transformer, a supplied jumper connects jacks 3 and 4. Jack 1 is the most rearward jack.
Despite the shipping damage, I ended up not doing much with the cabinet. I glued the rear wooden piece back together. The front metal panel has a scratch which I just left alone. The lid has a dent in the rear right corner which I left this alone as well. Other than that the original finish looks pretty good.
Inside the radio I found an inspection tag. On Feb. 25, 1929, Ray P. H…. thought this radio was OK.
So what is it? An Arborphone Grand or an Arborphone 25. I was doing some research on Google and found a 50 page document published by the Arborphone manufacturer in 1927. The first 40 pages or so describe the sales plan for 1927 and 28. The intention was to sell radios “scientifically” and is an interesting read. The last 10 pages describe the product line. One of the radios in the product line is this radio, however it is not called “Grand” rather it is called the Arborphone 25. Below are pages from that document that describe the Arborphone 25. I have yet to find a historical reference to an Arborphone model called “Grand”.
In addition to the table top model the Arborphone 25 was sold in three console models, the Arborphone 252, Arborphone 253 and Arborphone 255. Below, the first two pages are from the 1927 Catalog showing the table top version of the Arborphone 25. The last three pages are from the Dec/Jan 1927/28 Radio Age magazine. This article describes technical aspects of the Model 25 circuitry.
In addition to the table top model the Arborphone 25 was sold in three console models, the Arborphone 252, Arborphone 253 and Arborphone 255. Below, the first two pages are from the 1927 Catalog showing the table top version of the Arborphone 25. The last three pages are from the Dec/Jan 1927/28 Radio Age magazine. This article describes technical aspects of the Model 25 circuitry.
