AF3 or AF7

I am working on a Telefunken Super "Undine" T 875 WKK~ 1938/9.

The schematics asks for an AF3 tube (IF), however, in place there is an AF7 (a DRP, I think is not the original one of the radio but is a very old tube also).

The radio was not working (before I did start the restoration several modifications were made elsewhere).

Accordingly, with the tubes descriptions on Radio Museum, they are not interchangeable, but they are very similar on the specs.

Could I use anyone of them as a replacement in my restoration?

Many thanks,

 

Alvaro Ernani Georg

Brazil

YouTube Channel:

Rádios Antigos & Cia Ltda

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Hello Georg,

the AF3 has remote cut-off characteristic, while the AF7 has sharp cut-off characteristic.

If the AF7 is used in place of the AF3, distortions might occur on strong input signals.

Best Regards,
Jacob Roschy

 

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Vielen Dank Herr Roschy.

I will try to get an AF3 for my restoration.

Alvaro.

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