Using a ceramic disc cap for C700 creates the risk of discovering a "microphonic" capacitor. Not in the sense of picking up noise, but emitting a 'buzz' in step with your voice level heard inside the radio. Tram used the plastic film cap because it won't make any noise. The ceramic dielectric in most disc caps can become a tiny piezoelectric loudspeaker, vibrating with the amplitude of the RF passing through it, making noise from your voice audio.
Never did figure out how to predict which disc caps had this bad habit. Just learned to use a film cap like the factory did, but with a higher breakdown-voltage rating. They stay quiet.
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