F2A

F2A has no equivalent designation confirmed by the archive.

The F2A is a steep-slope power tetrode intended for long-distance communications (Nachrichtenweitverkehr). It is especially suitable as an output tube in single-ended, push-pull, and broadband power amplifiers, as well as for pulse circuits and control amplifiers.

Construction and Mounting

The F2A has a 9-pin long-distance communications tube base (9-Stift-Weitverkehrsröhrensockel) and fits a press-molded socket type Rel lp 29 b or a ceramic socket type Rel stv 9 a. It weighs approximately 70 g and can be mounted in any orientation. The tube has indirect heating, operable with AC or DC, with parallel supply.

Ratings

The heater voltage is 6.3 V, with a heater current of approximately 2.0 A ±0.15 A. Exceeding the permissible heater voltage variation of ±5% (absolute limits) impairs the operating behavior and service life. Maximum ratings include a screen-grid voltage of 425 V, a screen-grid dissipation of 5 W, a cathode current of 140 mA, a heater-to-cathode voltage of 120 V, a heater-to-cathode resistance of 20 kΩ, and a bulb temperature of 220 °C. The maximum grid-1 resistance is 0.3 MΩ when anode dissipation is ≤30 W, and 0.5 MΩ when anode dissipation is ≤20 W. With sine-wave continuous tone, the maximum output power must not exceed 30 W, otherwise the permissible maximum screen-grid dissipation is exceeded.

Characteristics

The grid-to-cathode capacitance is 18.5 pF ±1.5 pF, the anode-to-cathode capacitance is 13.0 pF ±1.0 pF, and the grid-to-anode capacitance is less than 0.8 pF. The transconductance is at least 12 mA/V when measured in triode connection. The grid-1 leakage current is given as at least 2 μA. In a typical operating point with anode voltage Ua = 250 V and cathode resistor Rk = 55 Ω, the anode current is 115 mA, the transconductance is 21 mA/V, the amplification factor is approximately 17, the internal anode resistance is 0.8 kΩ, and the load resistance is 1 kΩ. In a push-pull class AB operating point with anode voltage Ua = 425 V, grid-1 bias -Ug1 = 22 V, anode-to-anode load Raa = 5 kΩ, and screen-grid resistors Rg2 = 2×1.5 kΩ, the output power is 50 W with distortion k = 4%; at zero drive the anode current is 2×28 mA and screen-grid current is 2×4.5 mA, while at full drive (Ug1~ = 15 V) the anode current is 2×95 mA and screen-grid current is 2×20 mA. The datasheet includes characteristic curves labeled K 6 through K 17, covering single-ended class A, push-pull class AB, and push-pull class B operation.

Reliability

The datasheet states high reliability with a failure rate of approximately 1.5 per mille per 1000 hours. The datasheet by Siemens & Halske AG Wernerwerk für Bauelemente is referenced as RöK 3231/1.10.59.

Original manufacturer datasheets for F2A, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

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