12-29-2021, 03:38 PM
Gary
Since no one else has chimed in, I'll give it a go.
I am assuming this is the later version of model 20 with three trimmer condensers mounted to the tuning condenser.
Looking at the schematic, you will notice the first RF transformer's job is to couple the signals coming in on the longwire antenna to the first RF amplifier tube. The primary winding of this coil does not carry B+ voltage, only the signals out in the air.
The second and third RF transformers couple the amplified RF from the first stage to the second, and then from the second to third. Both of these have B+ on their primary windings. This, likely, is where they differ. In addition, the first RF transformer has one end of both the primary and secondary connected to ground, so it may only have two terminals with the grounded ends soldered to the mounting bracket of the coil (transformer).
I wouldn't be too concerned about the differences. The important thing is how many turns there are in the primaries of all three transformers. You already know the 2nd RF will be identical to the 3rd. Determine the number of turns and wire size of the primaries and you may proceed from there.
Oh, and just make sure you wind your new windings in the same direction as the originals.
Since no one else has chimed in, I'll give it a go.
I am assuming this is the later version of model 20 with three trimmer condensers mounted to the tuning condenser.
Looking at the schematic, you will notice the first RF transformer's job is to couple the signals coming in on the longwire antenna to the first RF amplifier tube. The primary winding of this coil does not carry B+ voltage, only the signals out in the air.
The second and third RF transformers couple the amplified RF from the first stage to the second, and then from the second to third. Both of these have B+ on their primary windings. This, likely, is where they differ. In addition, the first RF transformer has one end of both the primary and secondary connected to ground, so it may only have two terminals with the grounded ends soldered to the mounting bracket of the coil (transformer).
I wouldn't be too concerned about the differences. The important thing is how many turns there are in the primaries of all three transformers. You already know the 2nd RF will be identical to the 3rd. Determine the number of turns and wire size of the primaries and you may proceed from there.
Oh, and just make sure you wind your new windings in the same direction as the originals.
--
Ron Ramirez
Ferdinand IN
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