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I don't have this schematic but just a quick suggestion. Is this like an AA5 radio? The resistors in the couplates are probably OK if plate voltages look reasonable. You could try lifting the wire to the grid of the output tube and subbing a .01 cap between this grid and the plate of the previous tube. Ditto procedure on the grid of the first audio. Might get you by.

I have found that the Nutone web site will allow you to request diagrams. I was successful in getting what I needed, just a few months ago.

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You can also look up the diagrams of the couplates. There should be useful numbers on them.

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