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The 30 tube is a single triode configured as a grid leak detector. Notice the plate tied to ground. Since you say you have AVC voltage changes you can be sure the 30 is working. Can you see AVC voltage change when tuning on and off a known local radio station? Make sure C8 is .0005uf. If it's too large it will start filtering the audio.
Last edited by Kevin Kuehn; 12-21-2020 at 10:36 PM.
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