F2a

Name: F2a
Brand: Siemens

Beam Tetrode — StV9 — Siemens

Data: HighHigh quality — base, heater, all universal parameters present, and ≥50% of desirable parameters filled in. Safe to use for design decisions.

↗ 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)

EL12/425

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

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.

Pin Layout — StV9

1Control Grid (g1)

2Screen Grid (g2)

3Anode

References