07-13-2022, 10:03 AM
Rod
No. That is yes, I know this technique, but there are cons:
1. If I were to use DC on all tubes, we haved 6 tubes at 1.75A each. This makes it about 10A RMS. This said, I will need a bridge rectifier as the winding is not centertapped double voltage. 4 diodes, each dissipating roughly half that current times Vf which (Schottky could be used as the voltage is low) is about 0.4 - 0.6V. Lots of heat.
2. The voltage will be dropped by 2xVf. That is about 1V. Considering the filament voltage is 2.5V it is too much.
3. Yes I could bring DC to 47 tube only. Less current, but still a lot of reduction of the Filament voltage.
4. In either case a decent size capacitor is needed to filter the DC as the current is large.
5. Last but most important: I try to stick to original circuitry, except for cases where there is little choice, like dropping the voltage in AC/DC radios and using a capacitor to do that instead of huge resistors or curtain-burnere cords.
All in all, even though possible in theory, the early radios with low voltage / large current filament tubes are not the easiest to use DC for filaments.
No. That is yes, I know this technique, but there are cons:
1. If I were to use DC on all tubes, we haved 6 tubes at 1.75A each. This makes it about 10A RMS. This said, I will need a bridge rectifier as the winding is not centertapped double voltage. 4 diodes, each dissipating roughly half that current times Vf which (Schottky could be used as the voltage is low) is about 0.4 - 0.6V. Lots of heat.
2. The voltage will be dropped by 2xVf. That is about 1V. Considering the filament voltage is 2.5V it is too much.
3. Yes I could bring DC to 47 tube only. Less current, but still a lot of reduction of the Filament voltage.
4. In either case a decent size capacitor is needed to filter the DC as the current is large.
5. Last but most important: I try to stick to original circuitry, except for cases where there is little choice, like dropping the voltage in AC/DC radios and using a capacitor to do that instead of huge resistors or curtain-burnere cords.
All in all, even though possible in theory, the early radios with low voltage / large current filament tubes are not the easiest to use DC for filaments.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
