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These set are know for "silver mica disease" in the IF transformers - odd though that it appeared suddenly. The usual symptom is loud static crashes, but sometimes just no reception. The IF transformers have two capacitors for primary and secondary on a single mica disc. The B+ voltage will cause silver whiskers to grow across the gap (like electroplating) if there's any moisture present. When it gets close enough, voltage arcs across the gap and burns a little of the silver away, all of this over and over again...
The fix for this is to take the transformer apart and remove the mica disc, and put new capacitors on the terminals outside. If you have a capacitor tester with variable voltage, you can test this before digging in by testing for leakage between windings - obviously it has to stand at least 160V, since that's what it sees in the radio.
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