Virtual Valve Museum

Virtual Valve Museum

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NT39 / CV1222 / ACT6 Air Cooled Triode (ACT)

Size This valve measures 220mm x 50mm and has a 4-pin base.

This is an external anode triode designed to be air cooled.

Filament voltage 10V
Filament current 1.65A
Max anode voltage 1500V
Max anode dissipation 75W
Amplification factor 22
Mutual conductance 5.0mA/V
Anode impedance 4200 ohms
Max frequency for 75% anode rating 37MHz


Pin Function
1 n/c
2 Filament
3 Grid
4 Filament
TC Anode

Top view
Top view of the valve, above, and an internal view, below.
Inside view

The NT39/CV1222 above has "No. 3880c 38X"
etched on the glass under the part number.
The ACT6 below carries the number 7120.

Top quarter view Bottom quarter view