F2a — Beam Tetrode | Tubeofile

F2a

Beam Tetrode

Siemens

Known Equivalents & Substitutes

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

Similar Tubes (Not Drop-In Compatible)

Similar power pentode with different ratings — listed as similar by Radiomuseum

F2a11

Electrically identical — different socket (9-pin Weitverkehrsröhrensockel instead of Stahlröhrensockel)

Electrical Specifications

Section 1 — Beam Tetrode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)600V

Screen Voltage (max)Screen Voltage (max)425V

Anode Dissipation (max)Anode Dissipation (max)30W

Screen Dissipation (max)Screen Dissipation (max)5W

Cathode Current (max)Cathode Current (max)140mA

Heater-to-Cathode Voltage (max)Heater-Cathode Voltage (max)120V

Max Grid ResistorMax Grid Resistor0.3MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)250V

Screen Voltage (typical)Screen Voltage (typical)250V

Grid 1 Bias VoltageGrid 1 Bias Voltage (self-bias via Rk)-6.3V

Anode CurrentAnode Current100mA

Screen CurrentScreen Current

Output

Output PowerOutput Power10W

Load ImpedanceLoad Impedance2,200Ω

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance0.8pF

Input CapacitanceInput Capacitance18.5pF

Output CapacitanceOutput Capacitance13pF

Section 2 — Triode-Strapped

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)600V

Anode Dissipation (max)Anode Dissipation (max)30W

Cathode Current (max)Cathode Current (max)140mA

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)250V

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current2A

Notes

Base is EU-Telephone 9-pin Stahlröhrensockel (steel tube socket) — not a standard base in the catalog.
F2a11 uses 9-Stift-Weitverkehrsröhrensockel (9-pin telecommunications socket) — electrically identical.
Q(a+g2) combined dissipation max 30W — same as Pa_max, meaning total power budget is shared between anode and screen.
Rg1 max depends on anode dissipation: 0.3 MΩ at Pa ≤ 30W, 0.5 MΩ at Pa ≤ 20W.
Max bulb temperature 220°C.
End-of-life criteria: Ia ≤ 65 mA, S ≤ 12 mA/V, -Ig1 ≥ 2 µA (measured in triode connection at standard Kenndaten conditions).
Single-ended Class A pentode at Va=Vg2=250V, Ra=2.2kΩ, Rk=60Ω: Pout ≈ 10W at 10% THD.
Push-pull AB cathode-biased at Va=Vg2=250V, Raa=5kΩ, Rk=2×140Ω: Pout ≈ 20W.

References