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Ditto on the switching power supplies and computer equipment. That stuff generates all kinds of buzzing and hash.
As for the AVC issue try to find one of the IF secondary return leads and measure the voltage there while tuned to stations of varying signal strength, and compare. It's possible that a bypass capacitor was missed, and could be leaky enough to kill the AVC voltage. Also might be a good idea to check the pentodes in the RF/IF stages to see if perhaps some wise guy subbed in a different # that might have a different cutoff characteristic. Subbing in a sharp cutoff pentode where a remote cutoff type should be can upset the whole apple cart.
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