Quote:
Originally Posted by Kevin Kuehn
Since your set has AVC why not monitor that voltage to get a handle on what's going on? You'll want to use a VTVM, a scope, or a digital volt meter connected to the bottom side of R3(2meg). When the set is working does your AVC voltage seem to work normally with and without a signal tuned in? AVC voltage normally will be negative with a strong signal and become more positive as you de-tune the station. If the local oscillator isn't running you loose AVC action. If AVC voltage continues to respond to tuning then when the audio fades, then most likely you have an issue in the audio sections. When the radio is working correctly you can also align the IF's to the most negative voltage on the AVC line. There's really no need to rely on listening to an audio tone through the speaker.
Edit R3 not R4
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I did check the voltage at the AVC line resistor (R3) and it does respond like its supposed to but the audio is not very loud unless I use my signal generator's "HI" output connection, and then it comes out at a more "normal" volume level.
I have attributed that fact to what I believe is a faulty 1C6 Tube, because the oscillator seems to be "running" but not very well, and both 1A4 tubes respond with a hum when I touch their grid caps but nothing when I touch the grid cap on the 1C6, I get no hum out of it.
So I'm thinking I'm on the right track and just about have this thing going.