01-06-2023, 11:30 AM
Oops, sorry. Computer shut down and when I reentered the forum, I accidentally sent 2 messages. I am wordy enough on one message!
Yes, a 1N34 is a good try. I have to read through my US Navy "Basic Electronics" (John Rider, Publisher), a must for anyone new to the hobby, as it was originally written in the mid 1940s.
I did this on a Radiola 16 (a much easier radio to do this with), but I may have used a switching diode. I went from this diode to an external 2 stage amp. Disappointing, but still an improvement. Will try this eventually with a 1N31.
The RCA Receiving Tube Manual (I used a 1937 edition) states that both a diode detector and a grid leak detector can load down the previous stage more than a Biased detector can. the 24 Tetrodes and 27 Triode have less gain than later pentode tubes, but given the strength of current AM stations, this may not be an issue. The "Power Detector" can be changed to an audio amp merely by changing the cathode resistance. Find a schematic for a radio that uses a biased detector but has a radio / phono switch and this may give you an idea.
Ron Ramirez did an article on "bridging" AF Interstage on Philco 20s whose primaries opened. He recommends cap coupling on any Philco 20, not only to preserve the transformer but that the fidelity of the amp greatly improves. (However, the philco had a separate 1st AF and tetrode Biased Detector.
Direct injection of an audio signal will allow evaluation of the speaker, which due to a lack of compliance, is a weak link.
If you have another radio, especially a TRF, this experiment may be easier to do.
I will attach the detector section of the RCA Manual if U want, but I gotta go.
Yes, a 1N34 is a good try. I have to read through my US Navy "Basic Electronics" (John Rider, Publisher), a must for anyone new to the hobby, as it was originally written in the mid 1940s.
I did this on a Radiola 16 (a much easier radio to do this with), but I may have used a switching diode. I went from this diode to an external 2 stage amp. Disappointing, but still an improvement. Will try this eventually with a 1N31.
The RCA Receiving Tube Manual (I used a 1937 edition) states that both a diode detector and a grid leak detector can load down the previous stage more than a Biased detector can. the 24 Tetrodes and 27 Triode have less gain than later pentode tubes, but given the strength of current AM stations, this may not be an issue. The "Power Detector" can be changed to an audio amp merely by changing the cathode resistance. Find a schematic for a radio that uses a biased detector but has a radio / phono switch and this may give you an idea.
Ron Ramirez did an article on "bridging" AF Interstage on Philco 20s whose primaries opened. He recommends cap coupling on any Philco 20, not only to preserve the transformer but that the fidelity of the amp greatly improves. (However, the philco had a separate 1st AF and tetrode Biased Detector.
Direct injection of an audio signal will allow evaluation of the speaker, which due to a lack of compliance, is a weak link.
If you have another radio, especially a TRF, this experiment may be easier to do.
I will attach the detector section of the RCA Manual if U want, but I gotta go.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
