Cathode is brought out to two pins (pins 1 and 3) to reduce input impedance degradation at high frequencies. For input impedance measurements and optimal RF performance, both cathode pins must be connected to the input return; output circuit should connect to the other cathode pin.
Fixed bias is not recommended by Tesla datasheet. When using grid leak resistor of 0.2 MΩ, it is insufficient to develop the required negative bias — cathode bias resistor is needed.
Suppressor grid (g3) is brought out to a separate pin (pin 9) and is internally connected in the standard Noval base arrangement. Must be connected to cathode externally.
When used as video amplifier, gain between control grid input and cathode ray tube input should not exceed 25 to prevent microphonic effects.
Rg_max depends on bias method: 0.5 MΩ for fixed bias, 1 MΩ for cathode (self) bias.
Triode-strapped data sourced from Tom Schlangen 'Pentodes Strapped as Triodes' (2009 measured data table), not from the manufacturer datasheet.
Pin Layout — Noval
1Cathode
2Control Grid (g1)
3Cathode
Socket-Compatible Tubes ⚠ Not electrically compatible