The "Speaker" is not a conventional speaker. There is no magnet core, but a vibrator coil that picks up the frequency and produces the sound. The replacements you can find are simple magnet core speakers and work poorly.
The tubes are all the same inside and frequently to not work. You are correct, there is a simple point contact generator. Many times the tube must be gently cut open and the guts slipped out and the points cleaned.
Gandy
