10-02-2015, 10:27 PM
OK, here is a silly question. Troubleshooting for section 2 says to use an audio signal. Just to be sure, are you using an audio signal or an audio-modulated RF signal?
If you don't get any audio out of test point A, try walking your probe past C207, the volume control, and C210. At some point you'll get a signal, because you already know you get strong output from the 7C6 grid at point D. Then you'll have a good idea what was wrong between points A and D.
Ditto if you walk the audio signal from point A up to the IF transformer. If you are supposed to hear audio injected at point A, then you should hear it if it's injected anywhere along that path.
Is there a particular problem you are trying to solve? If you hear audio injected at point D, then you know the AF path works from the speaker back to that point regardless of your indication at point B, so I wouldn't sweat that for now. What do you hear when you turn the radio on and try to get a station, or if you put modulated RF on the grid of the IF tubes?
If you don't get any audio out of test point A, try walking your probe past C207, the volume control, and C210. At some point you'll get a signal, because you already know you get strong output from the 7C6 grid at point D. Then you'll have a good idea what was wrong between points A and D.
Ditto if you walk the audio signal from point A up to the IF transformer. If you are supposed to hear audio injected at point A, then you should hear it if it's injected anywhere along that path.
Is there a particular problem you are trying to solve? If you hear audio injected at point D, then you know the AF path works from the speaker back to that point regardless of your indication at point B, so I wouldn't sweat that for now. What do you hear when you turn the radio on and try to get a station, or if you put modulated RF on the grid of the IF tubes?
John Honeycutt
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