HF94 — Small Signal Pentode, B7G | Tubeofile

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HF94

Small Signal Pentode — B7G

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Mullard

↗ TDSL ↗ Radiomuseum

Known Equivalents & Substitutes

No known equivalents. If you know of any, use the ⚑ Report Issue button above.

Similar Tubes (Not Drop-In Compatible)

6AU6

American designation of EF94 — 6.3 V parallel heater, not series-string compatible

EF94

Identical electricals but 6.3 V parallel heater — not a drop-in in series-string heater circuits

XF94

600 mA series-heater variant (3.15 V) — different heater series, not interchangeable

Electrical Specifications

Section 1 — Pentode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)300V

Screen Voltage (max)Screen Voltage (max)300V

Anode Dissipation (max)Anode Dissipation (max)3.2W

Screen Dissipation (max)Screen Dissipation (max)0.65W

Cathode Current (max)Cathode Current (max)

Section 2 — Triode Strapped

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)150V

Anode Dissipation (max)Anode Dissipation (max)3W

Cathode Current (max)Cathode Current (max)20mA

Typical Operating

Anode ResistanceAnode Resistance7,500Ω

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.15A

Notes

Series-heater (150 mA) version of the EF94/6AU6. Electrically identical sections — only the heater voltage/current differs (12.6 V at 150 mA vs 6.3 V at 300 mA).
The H-prefix (150 mA series) is relatively uncommon — most series-string receivers used either 300 mA (P-prefix) or 100 mA (U-prefix) heater chains.
Suppressor grid (g3) is internally connected to cathode.
Vhk_max is 100 V DC (cathode positive relative to heater).

Pin Layout — B7G

1Control Grid

2Suppressor Grid (g3,internally connected to cathode)

3Heater

Socket-Compatible Tubes ⚠ Not electrically compatible

6BA6 EF91 EF94 XF94

20mA

Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)100V

Max Grid ResistorMax Grid Resistor1MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage250V

Screen Voltage (typical)Screen Voltage150V

Grid 1 Bias VoltageGrid 1 Bias Voltage-1V

Anode CurrentAnode Current10.8mA

Screen CurrentScreen Current3mA

Anode ResistanceAnode Resistance1,000,000Ω

TransconductanceTransconductance5.2mA/V

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance0.004pF

Input CapacitanceInput Capacitance5.5pF

Output CapacitanceOutput Capacitance5pF

TransconductanceTransconductance

4.8mA/V

Amplification Factor (μ)Amplification Factor (μ)36—

Heater

5Anode

6Screen Grid

7Cathode