Old TV show with old repaired radio playing old programming

[wa2ise]

I remember seeing long ago a TV show which had in its plot a mystery that a repaired old radio somehow could only receive old radio broadcasts. A kid repaired the radio. Think it was a car radio that used tubes? As if this radio became a time machine of sorts, receiving broadcasts transmitted decades before... Anyway, the "punch line" of the story was that the kid used the wrong oscillator coil, and ended up with a radio that picked up a local SW station that was playing old time radio programming. And only that station. The kid seemed disappointed by this mundane explanation, now that he finds out he didn't create a magic radio...

Well, it was a TV show, not a Shakespeare play.