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Power - Pentode (NOT beam) ·Pentode-Pentode

11AF9

Miniature dual-pentode television tube combining a high-current video-output section with a lower-power section for sound IF, AGC, or sync-separator service, integrating multiple television signal functions in one envelope.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: -
Socket code: -
Base pins: 10
Nominal heater: 11.6 V / 450 mA

Description

11AF9 — Dual Pentode Vacuum Tube

A miniature, dual-unit pentode vacuum tube designed for television receiver applications, featuring a high-transconductance video output pentode and a separate signal-processing pentode in a single envelope.

Overview

The 11AF9 is a multi-unit miniature vacuum tube containing two highly dissimilar pentodes designed for specific roles in television receivers. Unit No. 1 is optimized as a high-transconductance video output pentode, while Unit No. 2 is designed for signal-processing applications, including sound intermediate-frequency (IF) amplification, automatic gain control (AGC) amplification, or sync separation.

The tube is constructed with a 10-pin miniature base (basing configuration 10L) and requires a specialized miniature 10-contact socket. The 11AF9 is electrically identical to the 6AF9 except for its heater ratings, which are tailored for series-string heater chains.

Construction, Heater, and Physical Characteristics

The 11AF9 is housed in a miniature glass envelope conforming to Outlines section 6L, modified to accommodate a 10-pin base. The two pentode units are electrically independent with separate cathode connections, allowing them to operate at different bias levels. An internal shield (IS) is connected internally to minimize capacitive coupling and crosstalk between the two high-frequency pentode systems.

The heater is shared between both units and is designed for series-string operation. The heater characteristics of the 11AF9 and its sister type, the 6AF9, are compared below:

Parameter	11AF9	6AF9
Heater Voltage (AC/DC)	11.5 V	6.3 V
Heater Current	0.45 A	0.85 A
Calculated Heater Power	5.175 W	5.355 W
Peak Heater-Cathode Voltage	200 V max	200 V max

Direct Interelectrode Capacitances

To ensure stable operation in high-frequency and wideband applications, the interelectrode and inter-unit capacitances are tightly controlled. The direct interelectrode capacitances for each unit, measured without an external shield, are as follows:

Capacitance Parameter	Unit No. 1	Unit No. 2
Plate to All Other Electrodes (except Grid No. 1)	7 pF	11 pF
Grid No. 1 to All Other Electrodes (except Plate)	12 pF	10 pF
Plate to Grid No. 1	0.105 pF	0.140 pF
Grid No. 1 to Heater	—	0.140 pF

The isolation between the two pentode units is characterized by the following maximum inter-unit capacitances:

Plate of Unit No. 1 to Plate of Unit No. 2: 0.150 pF max
Grid No. 1 of Unit No. 1 to Grid No. 1 of Unit No. 2: 0.010 pF max
Plate of Unit No. 1 to Grid No. 1 of Unit No. 2: 0.100 pF max
Plate of Unit No. 2 to Grid No. 1 of Unit No. 1: 0.005 pF max

Class A1 Amplifier Maximum Ratings

The maximum ratings for the 11AF9 are established under the Design-Maximum system. These limits must not be exceeded under the worst-case operating conditions. The two units have highly asymmetrical power handling capabilities, reflecting their different intended applications:

Rating (Design-Maximum Values)	Unit No. 1 (Video Output)	Unit No. 2 (Signal Processing)
Plate Supply Voltage	550 V	550 V
Plate Voltage	250 V	250 V
Grid-No. 2 (Screen-Grid) Supply Voltage	550 V	550 V
Grid-No. 2 Voltage	250 V	250 V
Cathode Current	60 mA	15 mA
Plate Dissipation	5.1 W	1.5 W
Grid-No. 2 Input	2.5 W	0.5 W

Additionally, the maximum Grid-No. 1 circuit resistance for both units is limited to 1 megohm under typical operating conditions.

Electrical Characteristics and Operating Points

The typical operating characteristics of the two pentode units under Class A1 amplifier conditions highlight their distinct design optimizations:

Unit No. 1 (Video Output Pentode): Optimized for high transconductance and high current delivery to drive the capacitive load of a television picture tube. At a plate and screen voltage of 170 V, it exhibits an exceptionally high transconductance of 22,000 µmhos and a plate current of 30 mA.
Unit No. 2 (Sound IF / AGC / Sync Separator): Optimized for voltage amplification and signal processing. At a plate and screen voltage of 150 V, it operates at a lower plate current of 10 mA and a transconductance of 8,500 µmhos, with a higher internal plate resistance.

The typical operating parameters for both units are detailed below:

Parameter	Unit No. 1	Unit No. 2
Plate Voltage	170 V	150 V
Grid-No. 2 Voltage	170 V	150 V
Grid-No. 1 (Control-Grid) Voltage	-2.6 V	-2.1 V
Mu Factor (Grid No. 1 to Grid No. 2)	38	38
Internal Resistance	0.032 MΩ	0.16 MΩ
Transconductance	22,000 µmhos	8,500 µmhos
Plate Current	30 mA	10 mA
Grid-No. 2 Current	7.2 mA	3 mA

The grid-to-screen amplification factor (μ-factor from Grid No. 1 to Grid No. 2) is identical for both units at 38, indicating similar control grid-to-screen grid geometry, despite the significant differences in their overall plate current and transconductance capabilities.

Technical Summary

The 11AF9 is a specialized, high-performance miniature dual pentode featuring a 10-pin base and a 11.5 V, 0.45 A heater designed for series-string television receivers. By combining a high-power, high-transconductance video output pentode (Unit No. 1, with 5.1 W plate dissipation and 22,000 µmhos transconductance) and a medium-power signal-processing pentode (Unit No. 2, with 1.5 W plate dissipation and 8,500 µmhos transconductance) in a single envelope, the 11AF9 provides a compact and efficient solution for television receiver designs. Its controlled interelectrode capacitances and internal shielding ensure reliable, high-gain performance in demanding video and intermediate-frequency stages.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: -
Base pins: 10
Nominal heater voltage: 11.6 V
Nominal heater current: 450 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 32000 Ω
Transconductance: 0.022 S
Max plate voltage: 250 V
Max screen voltage: 250 V
Max plate dissipation: 5.1 W
Max screen dissipation: 2.5 W
Max cathode current: 60 mA

Video-output pentode.

Section 2

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 160000 Ω
Transconductance: 0.0085 S
Max plate voltage: 250 V
Max screen voltage: 250 V
Max plate dissipation: 1.5 W
Max screen dissipation: 0.5 W
Max cathode current: 15 mA

Sound IF, AGC amplifier, or sync-separator pentode.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

Plate to other electrodes
7 pF
Grid No.1 to other electrodes
12 pF
Plate to Grid No.1
0.105 pF

Other

Plate voltage
170 V
ClassA
Screen-grid voltage
170 V
ClassA
Control-grid voltage
-2.6 V
ClassA
Plate current
30 mA
ClassA
Screen-grid current
7.2 mA
ClassA

SECTION 2

Pentode

Capacitance

Plate to other electrodes
11 pF
Grid No.1 to other electrodes
10 pF
Plate to Grid No.1
0.14 pF

Other

Plate voltage
150 V
ClassA
Screen-grid voltage
150 V
ClassA
Control-grid voltage
-2.1 V
ClassA
Plate current
10 mA
ClassA
Screen-grid current
3 mA
ClassA