Electrically equivalent power pentode on Magnoval base — identical characteristics but anode on top cap instead of base pin 1, not pin-compatible
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Anode Voltage (max)400V
Screen Voltage (max)Screen Voltage (max)175V
Anode Dissipation (max)Anode Dissipation (max)10W
Cathode Current (max)Cathode Current (max, normal life)70mA
Typical Operating
Anode Voltage (typical)Anode Voltage200V
Screen Voltage (typical)Screen Voltage175V
Grid 1 Bias VoltageGrid 1 Bias Voltage-55V
Anode CurrentAnode Current50mA
Screen CurrentScreen Current
Heater
Heater VoltageHeater Voltage6.3V
Heater CurrentHeater Current0.6A
Notes
The Mullard datasheet provides two sets of absolute maximum ratings: normal life (Va_max=200V, Ik_max=70mA) and reduced life (Ik_max=100mA, bulb temp 220°C vs 180°C normal).
Despite being classified as a pentode, internal inspection reveals beam-forming plates within the anode cavity. The screen grid is formed from parallel fine wires; the control grid is a frame-grid construction extremely close to the cathode.
The typical operating point (Va=200V, Vg2=175V, Vg1=-55V) yields Ia=50mA with Ig2=5.5mA and gm=45mA/V — an unusually high transconductance for a power pentode.
Widely used in Tektronix oscilloscopes as the Y-amplifier final stage driving CRT deflection plates.
Va_max of 400V applies to the absolute maximum rating; the typical operating condition uses Va=200V.
Pins 2 and 6 are both suppressor grid (g3) connections, internally connected to cathode. Pins 7 and 9 are both cathode connections.