Скачать с ютуб BC 375 transmitter using a 6L6 tube instead of the VT 25 в хорошем качестве

BC 375 transmitter using a 6L6 tube instead of the VT 25

This is the BC-375 world-war 2 transmitter, which was used in the American "flying fortresses" during WWII. The BC-375 transmitter normally uses the VT-25 tube (10Y) as a microphone pre-amplifier that drives the push-pull power amplifier, which on its turn plate-modulates the RF power amplifier. Problem is; these VT-25 tubes have become ridiculously expensive on the used market, because of these audio nutcases who have been driving up the prices for the VT-25 like mad men. I see used VT-25 tubes go for as much as $200. As I am not willing to pay that ($200 actually bought me FOUR of the large VT-4C tubes that you also see in this video), I had to come up with an alternative. One important criterion for the alternative was that mods to the transmitter are NOT allowed. So I am now using a 6L6 audio penthode that I wired for triode mode (and also wired for directly heated); this means the 6L6 screen grid is tied to the anode (the "plate"), and the 6L6 cathode tied to one of the filament terminals (which is then the ground pin in the BC-375). I added a 5 ohm 5 watt resistor in series with the filament, so that the 6L6 tube "sees" the specified 6.3V filament voltage from the 7.5V that the VT-25 normally gets. As you can see in the video - it works PERFECT! Modulation sounds as good as with a VT-25, maybe even better than that!