06-09-2023, 06:18 PM
OK, no such luck.
Here's why. The tubes a 100mA and the summary of the volts is 20+20+50+60 is 150V. Which makes 120V insufficient. It will probably work, but not well, as the filament power will drop almost twice (150/110 square) or a bit les than twice but still a lot at 120V.
The resistances are thereby 1.5K plus 700 Ohm is 2.2K, which makes exactly 100mA at 220V.
Without the autotransformer I cannot bring the voltage up to 150V for the filaments.
I of course could do this: use 50+60 and a small resistance, and parallel that with 20+20 and a capacitor. But this is a lot of rerouting and I do not like rerouting things like it.
Thinking....thinking.....
I need overall impedance of 1,200 Ohm. The tubes are 400 Ohms together. I need 1.13K equiv. cap in series with two tubes with 20V filaments. This makes for 2.34uF cap.
Here's why. The tubes a 100mA and the summary of the volts is 20+20+50+60 is 150V. Which makes 120V insufficient. It will probably work, but not well, as the filament power will drop almost twice (150/110 square) or a bit les than twice but still a lot at 120V.
The resistances are thereby 1.5K plus 700 Ohm is 2.2K, which makes exactly 100mA at 220V.
Without the autotransformer I cannot bring the voltage up to 150V for the filaments.
I of course could do this: use 50+60 and a small resistance, and parallel that with 20+20 and a capacitor. But this is a lot of rerouting and I do not like rerouting things like it.
Thinking....thinking.....
I need overall impedance of 1,200 Ohm. The tubes are 400 Ohms together. I need 1.13K equiv. cap in series with two tubes with 20V filaments. This makes for 2.34uF cap.
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.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
