10AL11 — Dissimilar Double Pentode Compactron

The 10AL11 is a multi-unit vacuum tube of the compactron design, combining two dissimilar pentode sections within a single T-9 glass envelope. It features a sharp-cutoff, dual-control pentode (Section 2) and a high-power pentode (Section 1). This device is primarily designed for television receiver applications, where the dual-control pentode serves as an FM detector and the power pentode operates as an audio-frequency output amplifier.

Construction, Heater, and Pinout

The 10AL11 is constructed in a T-9 glass bulb with a 12-pin button duodecar base (E12-70 outline, JEDEC 9-58). The tube features coated unipotential cathodes and can be operated in any mounting position.

The heater is designed for series-string or parallel operation with a nominal voltage of 9.8 V and a current of 0.6 A (600 mA), with a controlled warm-up time of 11 seconds. The heater current limits are specified at 600 ± 40 mA. The heater-to-cathode voltage ratings are:

• Heater positive with respect to cathode: 100 V maximum DC component, 200 V maximum total DC and peak.
• Heater negative with respect to cathode: 200 V maximum total DC and peak.

The JEDEC 12BU basing diagram defines the pin connections as follows:

• Pin 1: Heater (H)
• Pin 2: Cathode, Section 2 (2K)
• Pin 3: Grid No. 1, Section 2 (2G1)
• Pin 4: Grid No. 3, Section 2 (2G3)
• Pin 5: Internal Shield (IS)
• Pin 6: Plate, Section 2 (2P)
• Pin 7: Grid No. 2, Section 2 (2G2)
• Pin 8: Grid No. 1, Section 1 (1G1)
• Pin 9: Cathode and Grid No. 3, Section 1 (1K, 1G3)
• Pin 10: Grid No. 2, Section 1 (1G2)
• Pin 11: Plate, Section 1 (1P)
• Pin 12: Heater (H)

Section 1: Beam Power Unit (Power Pentode)

Section 1 is a power pentode designed for Class A1 audio amplification. It is capable of delivering moderate power output with low distortion when driven by typical audio-frequency signals.

Maximum Ratings (Design-Maximum Values)

• Plate Voltage: 275 V
• Grid No. 2 (Screen-Grid) Voltage: 275 V
• Plate Dissipation: 10 W
• Grid No. 2 Input: 2 W

Typical Operation (Class A1 Amplifier)

At a typical operating point, the power pentode exhibits the following characteristics:

• Plate Voltage: 250 V
• Grid No. 2 Voltage: 250 V
• Grid No. 1 (Control-Grid) Voltage: -8 V
• Peak AF Grid No. 1 Voltage: 8 V
• Zero-Signal Plate Current: 35 mA
• Maximum-Signal Plate Current: 39 mA
• Zero-Signal Grid No. 2 Current: 2.5 mA
• Maximum-Signal Grid No. 2 Current: 7 mA
• Plate Resistance (Approx.): 0.1 MΩ
• Transconductance: 6500 µmhos
• Load Resistance: 5000 Ω
• Total Harmonic Distortion: 10%
• Maximum-Signal Power Output: 4.2 W

Maximum Circuit Values

• Grid No. 1 Circuit Resistance (Fixed Bias): 0.25 MΩ
• Grid No. 1 Circuit Resistance (Cathode Bias): 0.5 MΩ

Section 2: Pentode Unit (Dual-Control Pentode)

Section 2 is a sharp-cutoff, dual-control pentode designed for FM detector service. It features independent control grids (Grid No. 1 and Grid No. 3) that allow dual-signal modulation or gated detection.

Maximum Ratings (Design-Maximum Values)

• Plate Voltage: 330 V
• Grid No. 3 (Suppressor-Grid) Voltage: 28 V
• Grid No. 2 Supply Voltage: 330 V
• Grid No. 1 Voltage (Positive DC): 0 V
• Plate Dissipation: 1.7 W
• Grid No. 2 Input:
  • For Grid No. 2 voltages up to 165 V: 1.1 W
  • For Grid No. 2 voltages between 165 V and 330 V: Must be limited in accordance with the Grid No. 2 rating chart (decreasing to 0 W at 330 V).

Characteristics and Typical Operation (Class A1)

• Plate Supply Voltage: 150 V
• Grid No. 3 Voltage: 0 V
• Grid No. 2 Supply Voltage: 100 V
• Cathode-Bias Resistor: 560 Ω
• Plate Resistance (Approx.): 0.15 MΩ
• Grid No. 1 to Plate Transconductance: 1000 µmhos
• Grid No. 3 to Plate Transconductance: 400 µmhos
• Plate Current: 1.3 mA
• Grid No. 2 Current: 2.1 mA
• Grid No. 1 Voltage (Approx.) for Plate Current of 30 µA: -4.5 V
• Grid No. 3 Voltage (Approx.) for Plate Current of 50 µA: -4.5 V

Interelectrode Capacitances

The direct interelectrode capacitances of the 10AL11 are specified separately for each section, along with the capacitive coupling between the two plates.

Related Designations

The 10AL11 belongs to a family of identical compactrons that differ only in their heater configurations:

• 6AL11: Designed for a 6.3 V, 0.9 A heater supply.
• 12AL11: Designed for a 12.6 V, 0.45 A heater supply with an 11-second warm-up time.

All other physical dimensions, pinouts, capacitances, and electrical ratings remain identical across these three designations.

Technical Summary

The 10AL11 is a versatile duodecar-based compactron containing a high-power pentode and a dual-control sharp-cutoff pentode. By integrating these two distinct functions into a single T-9 envelope, it simplifies the design of FM detection and audio output stages in television receivers. Operating with a 9.8 V, 0.6 A heater, the device provides robust performance, offering up to 4.2 W of audio output from Section 1 and precise dual-control detection capabilities from Section 2.