Hi all;
I am restoring a Model 20A and need to replace an inter-stage transformer RF coil shown in the schematic as number 7.
This is one of the type mounted on a hollow tube like a toilet paper roll and inserted head into a metal can.
Any pointers to where I can find a replacement would be greatly appreciated. See attached schematic for reference.
Thanks.
Howard
So what is the issue w/ the one in the set??
It appears to have a broken wire in the primary winding, but I have not pulled it out of the metal can yet as I want to line up a replacement in case its beyond me to fix.
Very common issue on the early sets. Pretty simple to fix. Primary winding is on the outside so it's easy to remove and rewind w/new wire. Wire gauge isn't particularly crucial something like 32-40ga is fine. It's not a tuned circuit so the # of turns isn't critical abt 50 is good. The phasing (direction) dosen't matter.
I suppose you could cheat and use a resistor and cap to supply the hv to the 24A plate and a cap to couple the rf signal the secondary of the coil.
GL
If you have to rewind an open primary on an RF coil, which is what I think you are describing, then it would be best to wind it in the same direction as the original winding.
Regards
Arran
Isn't there an article here as to how to use just the secondary of the 20 interstage?
The original title of this thread was confusing.
Part (7) is the 2nd RF coil,
not the set's interstage transformer. That is part (21).
I changed the title of this thread accordingly.
![[Image: 20b.jpg]](http://www.philcoradio.com/images/phorum/schem/20b.jpg)
A-ha! Well, as Terry said, those are not too difficult to rewind.
Interesting ideas. Thanks for the suggestion, although I think the number of windings is important to keep the impedience and the resulting voltage on the secondary in the acceptable range.
Terry is correct. Of course it is best to rewind to the specs, but in this particular case it is not overly important (within reason).
My apologies for misdescribing the RF coil. Being new to restoring old radios I have all I can do to keep my hands steady when working under the chassis.