Pen4VB

Power Pentode — B7G

Mullard

Known Equivalents & Substitutes

Similar Tubes (Not Drop-In Compatible)

AC2/Pen

Radiomuseum lists as normally replaceable — similar power pentode

N41

Radiomuseum lists as normally replaceable alternative

PT4

Radiomuseum lists as normally replaceable — similar Mullard power pentode

Electrical Specifications

Typical Operating

Anode Voltage (typical)Plate Voltage250V

Grid 1 Bias VoltageGrid Voltage-5.8V

Screen VoltageScreen Voltage100V

TransconductanceTransconductance10mA/V

Cathode Resistor (self-bias)Self-Bias Cathode Resistor

Heater

Heater VoltageHeater Voltage4V

Heater CurrentHeater Current1.95A

Notes

Unusually high transconductance (gm = 10 mA/V) for a 1930s power pentode.
Self-bias: 145 ohms cathode resistor needed for -5.8V bias at Va=250V, Vg2=100V.
Uses the old British 7-pin base (M7A) — not to be confused with the later B7G miniature base.
Brans Vademecum table Vc lists PenA4 and UCL82 as equivalents, though UCL82 is a triode-pentode compound tube and not a true equivalent.
Production era: primarily 1931-1937 per Radiomuseum documentation.

Pin Layout — B7G

1Anode

2Screen Grid (g2)

3Control Grid (g1)

4