Transformer - Audio Interstage, 10 mA

These transformers will work in about any 1920s radio. They are an inexpensive fix for most radios from the 1920s and can be used in other applications. They used to offer this transformer without the iron, just the coil by its self which could be used to replace the open coil in some radio transformers. That way you were able to keep the old transformer and have a new coil in it. I wish they still offered those. The only drawback on these is that they do not have as much bass to them as many of the original transformers had.

I used two of these transformers in an Atwater Kent model 20 TRF receiver. The transformers fit inside the two metal cans that the original transformers were in. When looking in the radio you can't tell it has new transformers. If you take the radio out of the cabinet you can see the new wires, but that is okay. The radio now works.

I bought a Freed-Eisemann broadcast Radio, NR6, from and estate. The two audio transformers were open. I bought two P-T156 transformers from antique electronic supply. There were $16.95 each. The new transformers were mounted under the chassis of the radio and can’t be seen from the top. The primary on the new transformers are the red and blue wires which are connected to the plate of each of the audio tubes. On January 13, 2019 the radio worked for the first time in years. I used an Arbe-III battery eliminator to power it. I don’t have a matching speaker so I used a modern one. I used an audio transformer that I took out of a small radio to go between the radio and the speaker. The transformer is for a 50C5 tube. The two transformers work fine in this application.

I bought this interstage for an older '65 Gibson GA-15 RVT. Figured I'd give it a try. From what I was able to find the original turns ratio for the Gibson interstage was like 2.4 to 2.5. Figured at worse I'd have to maybe tweak things a bit. Not sure how things may turn out for others with this amp, but the voltages, sound, response, etc using this interstage seems to be pretty much spot on. So, I'm going to run with this and see how it holds up to the test of time ;)

These units work great to replace most audio transformers in the 20's battery sets. They are small enough to many times fit inside the original clamshell housings so the end result looks original. Out of the dozen or so I have bought I only had one that was defective. (shorts in the secondary winding) Test them immediately after getting them so you can send it back if it is shorted.