01-08-2022, 11:21 AM
The 1j37b and 1j42a can also be used as the earliest ever kind of triode, the Gammatron.
Use one of g1a and g1b as the anode and the other as the grid. Tie actual anode, g2 and g3 to 0V or f-.
It won't work very well, but neither did the originals, hence the second idea was the open wire or mesh between the cathode and anode.
What you can't do with a rod tube is simulate the Tetrode for a tetrode negative resistance oscillator. You can with a real pentode on some tubes by connecting g2 to g3, or even ignoring g3 (suppressor grid). The rod tubes are NOT pentodes, just same number of grids and similar anode characteristics. Hence when triodising you connect g3 to 0V, f- or f+, never to anode and g2 as with real pentodes. The EF80 and DF97 are often triodised at VHF for mixer-oscillator use, in which case g2, g3 and anode are shorted.
In common grid mode you need a pentode where g3 has a separate pin, not connected to filament or cathode. It goes to 0V. A battery valve/rod tube CAN be used in common grid mode. The f+ and f- are fed by RF chokes from LT- & LT+ and the RF signal via caps to f- and f+. At lower frequency where a core is needed to get enough inductances you use like a 1:1 transformer with the f- and f+ DC cancelling (think of bias cancels in a push pull transformer).
Use one of g1a and g1b as the anode and the other as the grid. Tie actual anode, g2 and g3 to 0V or f-.
It won't work very well, but neither did the originals, hence the second idea was the open wire or mesh between the cathode and anode.
What you can't do with a rod tube is simulate the Tetrode for a tetrode negative resistance oscillator. You can with a real pentode on some tubes by connecting g2 to g3, or even ignoring g3 (suppressor grid). The rod tubes are NOT pentodes, just same number of grids and similar anode characteristics. Hence when triodising you connect g3 to 0V, f- or f+, never to anode and g2 as with real pentodes. The EF80 and DF97 are often triodised at VHF for mixer-oscillator use, in which case g2, g3 and anode are shorted.
In common grid mode you need a pentode where g3 has a separate pin, not connected to filament or cathode. It goes to 0V. A battery valve/rod tube CAN be used in common grid mode. The f+ and f- are fed by RF chokes from LT- & LT+ and the RF signal via caps to f- and f+. At lower frequency where a core is needed to get enough inductances you use like a 1:1 transformer with the f- and f+ DC cancelling (think of bias cancels in a push pull transformer).
