04-05-2021, 02:03 PM
The drama surrounding the 2nd detector and the IF signal is finally solved ! Today my parts arrived from Dave Cantelon at Just Radios. Among therm were 100 pf and 110 pf condensers. I installed the missing 100 pf condensers in the 2nd IF can...
[Image: https://64.media.tumblr.com/5ec1fe785df6...040f0f.jpg]
I had also tested the IF (6K7G) and 2nd detector (6Q7G) tubes before this, and found that the 6Q7G I was using had gone bad. It lit up OK, but it was completely dead under test ! How it managed to pass the audio signal I don't know, or much care. I believe this was the main source of my frustration. I didn't bother to even try the radio again until after I had received and installed the 100 pf condensers. Once that was done, I set about seeing if I could finally re-align the radio. As soon as I turned it on, with my signal generator set for 470KC I was able to hear a signal when I injected the signal through a .01 MFD condenser into the grid of the IF amp.I tuned and peaked the 2nd IF transformer, then moved the input to the grid of the first detector (6A8G), and tuned and peaked the 1st IF transformer. With that done, I moved the signal input to the antenna input , and, following the alignment instructions, peaked things up finally. After that I proceeded with the rest of the alignment as the instructions describe, and everything went pretty smoothly. Tonight I will do final tweaks, and then test the radio on my outdoor antenna.
[Image: https://64.media.tumblr.com/5ec1fe785df6...040f0f.jpg]
I had also tested the IF (6K7G) and 2nd detector (6Q7G) tubes before this, and found that the 6Q7G I was using had gone bad. It lit up OK, but it was completely dead under test ! How it managed to pass the audio signal I don't know, or much care. I believe this was the main source of my frustration. I didn't bother to even try the radio again until after I had received and installed the 100 pf condensers. Once that was done, I set about seeing if I could finally re-align the radio. As soon as I turned it on, with my signal generator set for 470KC I was able to hear a signal when I injected the signal through a .01 MFD condenser into the grid of the IF amp.I tuned and peaked the 2nd IF transformer, then moved the input to the grid of the first detector (6A8G), and tuned and peaked the 1st IF transformer. With that done, I moved the signal input to the antenna input , and, following the alignment instructions, peaked things up finally. After that I proceeded with the rest of the alignment as the instructions describe, and everything went pretty smoothly. Tonight I will do final tweaks, and then test the radio on my outdoor antenna.
