03-29-2021, 07:11 PM
I have been hunting down the problems which sprang up with this 38-10. If I inject an audio signal at the grid of the 6F6 it comes booming in loud and clear. If I inject it at either the wiper of the volume pot, or the terminal fed from the 2nd IF transformer, I get a lower signal which can be controlled by the volume pot. I believe this means the audio signal is getting through the 6Q7 triode section. Between the side of C22 which is shown connected to the green wire and the high fed terminal of the volume pot, I read a bout 51K, which is what the schematic shows it should be.Here are two pictures of the schematic, the first the full schematic, the second a close up of the area being discussed...
[Image: https://64.media.tumblr.com/c42db0749b4a...0af14f.jpg]
[Image: https://64.media.tumblr.com/67df47595e3c...5a2d90.jpg]
I have checked C22 with my capacitance checker, which shows it well within tolerance, at least at low voltage. Yesterday I took apart the 2nd IF, removed the can to ring out the windings, and found R21 lurking inside. R21 checked out to be approximately correct for 51K. The windings also rang out a little less than 10 ohms, and seemed about right. I didn't check C23 or C24. I am getting no feed through of a modulated IF signal when I inject it at the antenna input, or even if I inject it at the green wire side of C22, or the other diode plate for that matter. It is not demodulating it and converting it to audio. I wonder, could the problem be with C22, C23, or C24? Any ideas? Yes, I have even swapped out the 6Q7G just to be sure it wasn't the tube. Any help or suggestions will be appreciated.
[Image: https://64.media.tumblr.com/c42db0749b4a...0af14f.jpg]
[Image: https://64.media.tumblr.com/67df47595e3c...5a2d90.jpg]
I have checked C22 with my capacitance checker, which shows it well within tolerance, at least at low voltage. Yesterday I took apart the 2nd IF, removed the can to ring out the windings, and found R21 lurking inside. R21 checked out to be approximately correct for 51K. The windings also rang out a little less than 10 ohms, and seemed about right. I didn't check C23 or C24. I am getting no feed through of a modulated IF signal when I inject it at the antenna input, or even if I inject it at the green wire side of C22, or the other diode plate for that matter. It is not demodulating it and converting it to audio. I wonder, could the problem be with C22, C23, or C24? Any ideas? Yes, I have even swapped out the 6Q7G just to be sure it wasn't the tube. Any help or suggestions will be appreciated.