Virtual Valve Museum

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STC CV28 / 3J/121E air cooled triode

SIze This valve measures 340x90mm overall (50mm across the copper anode), not including the connection straps.

The data for this valve says that a CV28 with no cooling fins is a CV1994. However, this valve is labelled as faulty and it is likely that the fins were never fitted due to this.

Filament voltage (1) 15.6V
Filament current 22A
Max anode voltage 10kV
Max anode dissipation (2) 800W
Mutual conductance (3) 3.1mA/V
Anode impedance (3) 12.5k ohms
Amplification factor (3) 40
Max total emission:
Less than 30MHz 10kV/400mA
up to 30MHz 5kV/400mA
up to 60MHz 4kV/400mA
Cin nom 23.2pF
Cout nom 1.6pF
Ca, g1 nom 15.9pF

(1) Valves are marked with the filament voltage which may differ from valve to valve

(2) With forced air cooling this figure can be 1.1kW

(3) At Va=5kV, Ia=200mA

Connections: The longer strap leads are the filament.


Inside view Label Label