Hello I have an early 1920's TRF radio.

Both RF interstate coupling transformers are open.
The original tubes were of the WD11 typed.
I plan on replacing them with 30's for (RF) and 20's for (audio) as replacements.

The original RF coupling transformers were of the "Radio Service Laboratories" type.
A black can with iron** power. (it is conductive)

I ohmed out the primary and secondary: Both have 30 ohms resistance.

Because the resistance is equal, can I assume these are non-amplifying type.

Does AES have a suitable replacement?

Thanks very much in advance.

Hello John, Why do you think the old transformers are bad? I'm a little surprised that the resistance of both windings are the same and I would expect them to be somewhat higher but usually if they're not open they're OK. I'd try them out before changing them. You shouldn't have much trouble replacing them if you have to. Try Playthings of the past http://www.oldradioparts.com/ they should have both old transformers and new versions. Also AES www.tubesandmore.com stock a suitable range including replacement windings to fit on the old core if it's the right size. The 30 tubes will work OK but I'd suggest a 31 output triode for the final stage, it's got a 2 volt filament to complement the 30s.
Don Black.
: Hello I have an early 1920's TRF radio.

: Both RF interstate coupling transformers are open.
: The original tubes were of the WD11 typed.
: I plan on replacing them with 30's for (RF) and 20's for (audio) as replacements.

: The original RF coupling transformers were of the "Radio Service Laboratories" type.
: A black can with iron** power. (it is conductive)

: I ohmed out the primary and secondary: Both have 30 ohms resistance.

: Because the resistance is equal, can I assume these are non-amplifying type.

: Does AES have a suitable replacement?

: Thanks very much in advance.

Hi John, The WD11 has an unique base, different to the usual 4 pin UX used by the 20, 30, 31, etc. If you want to substitute such tubes you'll have to either change the sockets, use an adaptor or simulate the WD11.
I think Norm leal might have some useful advice on this.
Don Black.

: Hello John, Why do you think the old transformers are bad? I'm a little surprised that the resistance of both windings are the same and I would expect them to be somewhat higher but usually if they're not open they're OK. I'd try them out before changing them. You shouldn't have much trouble replacing them if you have to. Try Playthings of the past http://www.oldradioparts.com/ they should have both old transformers and new versions. Also AES www.tubesandmore.com stock a suitable range including replacement windings to fit on the old core if it's the right size. The 30 tubes will work OK but I'd suggest a 31 output triode for the final stage, it's got a 2 volt filament to complement the 30s.
: Don Black.
: : Hello I have an early 1920's TRF radio.

: : Both RF interstate coupling transformers are open.
: : The original tubes were of the WD11 typed.
: : I plan on replacing them with 30's for (RF) and 20's for (audio) as replacements.

: : The original RF coupling transformers were of the "Radio Service Laboratories" type.
: : A black can with iron** power. (it is conductive)

: : I ohmed out the primary and secondary: Both have 30 ohms resistance.

: : Because the resistance is equal, can I assume these are non-amplifying type.

: : Does AES have a suitable replacement?

: : Thanks very much in advance.

Hello,

Actually one of the two RF interstage transformers is missing from the radio.
Based on the footprint of the missing item, I am assuming it to be identical to the
one that is there.

The RFT that is present had the primary winding open. When I unscrewed the can the open was near the terminal allowing me to measure the resistance.
It could be reconnected, but the overall appearance inside the can looks troublesome.

I guess I should really reconnect it and measure and physical characteristics.

With regard to the WD11. Fortunately, I have a junker TRF with some parts:

301 x 3
201 x 2
tube bases.

I would like to use what I have if that makes sense.

I have found some previous information (postings) from Norm.
But I am sure I am going to have additional challenges and questions.

Thanks for your help!

john

: Hi John, The WD11 has an unique base, different to the usual 4 pin UX used by the 20, 30, 31, etc. If you want to substitute such tubes you'll have to either change the sockets, use an adaptor or simulate the WD11.
: I think Norm leal might have some useful advice on this.
: Don Black.

: : Hello John, Why do you think the old transformers are bad? I'm a little surprised that the resistance of both windings are the same and I would expect them to be somewhat higher but usually if they're not open they're OK. I'd try them out before changing them. You shouldn't have much trouble replacing them if you have to. Try Playthings of the past http://www.oldradioparts.com/ they should have both old transformers and new versions. Also AES www.tubesandmore.com stock a suitable range including replacement windings to fit on the old core if it's the right size. The 30 tubes will work OK but I'd suggest a 31 output triode for the final stage, it's got a 2 volt filament to complement the 30s.
: : Don Black.
: : : Hello I have an early 1920's TRF radio.

: : : Both RF interstate coupling transformers are open.
: : : The original tubes were of the WD11 typed.
: : : I plan on replacing them with 30's for (RF) and 20's for (audio) as replacements.

: : : The original RF coupling transformers were of the "Radio Service Laboratories" type.
: : : A black can with iron** power. (it is conductive)

: : : I ohmed out the primary and secondary: Both have 30 ohms resistance.

: : : Because the resistance is equal, can I assume these are non-amplifying type.

: : : Does AES have a suitable replacement?

: : : Thanks very much in advance.

Hello John, Good luck with the restoration. You might already be aware that the 201A and C301A tubes were all made by RCA but the C301As were badged and sold as Cunninham brand tubes under a licensing agreement i.e. they should be identical tubes (except for markings) and sockets.
Don Black.
: Hello,

: Actually one of the two RF interstage transformers is missing from the radio.
: Based on the footprint of the missing item, I am assuming it to be identical to the
: one that is there.

: The RFT that is present had the primary winding open. When I unscrewed the can the open was near the terminal allowing me to measure the resistance.
: It could be reconnected, but the overall appearance inside the can looks troublesome.

: I guess I should really reconnect it and measure and physical characteristics.

: With regard to the WD11. Fortunately, I have a junker TRF with some parts:

: 301 x 3
: 201 x 2
: tube bases.

: I would like to use what I have if that makes sense.

:
: I have found some previous information (postings) from Norm.
: But I am sure I am going to have additional challenges and questions.

: Thanks for your help!

: john

: : Hi John, The WD11 has an unique base, different to the usual 4 pin UX used by the 20, 30, 31, etc. If you want to substitute such tubes you'll have to either change the sockets, use an adaptor or simulate the WD11.
: : I think Norm leal might have some useful advice on this.
: : Don Black.

: : : Hello John, Why do you think the old transformers are bad? I'm a little surprised that the resistance of both windings are the same and I would expect them to be somewhat higher but usually if they're not open they're OK. I'd try them out before changing them. You shouldn't have much trouble replacing them if you have to. Try Playthings of the past http://www.oldradioparts.com/ they should have both old transformers and new versions. Also AES www.tubesandmore.com stock a suitable range including replacement windings to fit on the old core if it's the right size. The 30 tubes will work OK but I'd suggest a 31 output triode for the final stage, it's got a 2 volt filament to complement the 30s.
: : : Don Black.
: : : : Hello I have an early 1920's TRF radio.

: : : : Both RF interstate coupling transformers are open.
: : : : The original tubes were of the WD11 typed.
: : : : I plan on replacing them with 30's for (RF) and 20's for (audio) as replacements.

: : : : The original RF coupling transformers were of the "Radio Service Laboratories" type.
: : : : A black can with iron** power. (it is conductive)

: : : : I ohmed out the primary and secondary: Both have 30 ohms resistance.

: : : : Because the resistance is equal, can I assume these are non-amplifying type.

: : : : Does AES have a suitable replacement?

: : : : Thanks very much in advance.

RSL trannies aren't common but you might find one with enough advertising. I expect they are broadly resonant in the lower half of the broadcast band, and some brands are wound with resistance wire to make sure they're broad. Some are pretty crude-looking inside, too. 1923 vintage, maybe 1922.