17C9 — Sharp-Cutoff Dual Tetrode Vacuum Tube

A miniature, sharp-cutoff dual tetrode designed for VHF RF-amplifier and autodyne mixer applications in electronic equipment.

Overview

The 17C9 is a specialized miniature vacuum tube containing two independent sharp-cutoff tetrode units within a single envelope. It is designed primarily for high-frequency applications, specifically as a Very High Frequency (VHF) RF-amplifier and as an autodyne mixer. The 17C9 is electrically identical to the 6C9 except for its heater ratings, which are designed for series-string heater configurations.

Construction, Heater, and Physical Characteristics

The 17C9 is housed in a glass envelope conforming to outlines section 6B, with the modification of an added center pin on the base. Because of this unique base configuration, the tube requires a specialized miniature 10-contact socket for operation. The internal construction features a common internal shield that is connected to the cathode of Unit 2.

Heater Ratings

The heater is designed for operation from either an AC or DC supply with the following parameters:

• Heater Voltage (AC/DC): 16.8 V
• Heater Current: 0.15 A
• Peak Heater-Cathode Voltage: 100 V maximum

Pinout Configurations (Base 10F)

Two distinct pinout configurations are documented for the 10F base of the 17C9. Both configurations utilize the center pin for the Cathode of Unit 2 and the Internal Shield ($K_{TR2}, IS$):

Configuration A

• Pin 1: Grid No. 2 of Unit 1 ($G_{2TR1}$)
• Pin 2: Grid No. 1 of Unit 1 ($G_{1TR1}$)
• Pin 3: Plate of Unit 2 ($P_{TR2}$)
• Pin 4: Heater ($H$)
• Pin 5: Heater ($H$)
• Pin 6: Cathode of Unit 1 ($K_{TR1}$)
• Pin 7: Grid No. 1 of Unit 2 ($G_{1TR2}$)
• Pin 8: Grid No. 2 of Unit 2 ($G_{2TR2}$)
• Pin 9: Plate of Unit 1 ($P_{TR1}$)
• Center Pin: Cathode of Unit 2, Internal Shield ($K_{TR2}, IS$)

Configuration B

• Pin 1: Heater ($H$)
• Pin 2: Plate of Unit 2 ($P_{TR2}$)
• Pin 3: Grid No. 2 of Unit 2 ($G_{2TR2}$)
• Pin 4: Grid No. 1 of Unit 2 ($G_{1TR2}$)
• Pin 5: Heater ($H$)
• Pin 6: Cathode of Unit 1 ($K_{TR1}$)
• Pin 7: Grid No. 1 of Unit 1 ($G_{1TR1}$)
• Pin 8: Grid No. 2 of Unit 1 ($G_{2TR1}$)
• Pin 9: Plate of Unit 1 ($P_{TR1}$)
• Center Pin: Cathode of Unit 2, Internal Shield ($K_{TR2}, IS$)

Direct Interelectrode Capacitances

The internal shielding and physical separation of the two tetrode units provide low capacitive coupling. The direct interelectrode capacitances are specified as follows:

Individual Unit Capacitances

Unit-to-Unit Capacitances

• Plate of Unit 1 to Plate of Unit 2: 0.003 max pF
• Grid No. 1 of Unit 1 to Grid No. 1 of Unit 2: 0.001 max pF
• Grid No. 1 of Unit 1 to Plate of Unit 2: 0.001 max pF
• Grid No. 1 of Unit 2 to Plate of Unit 1: 0.032 max pF

Electrical Characteristics and Operating Points

Under typical Class A1 amplifier operating conditions, each tetrode unit exhibits the following characteristics:

• Plate Voltage: 125 V
• Grid-No. 2 (Screen-Grid) Voltage: 80 V
• Grid-No. 1 (Control-Grid) Voltage: -1 V
• Plate Resistance (Approximate): 0.1 MΩ
• Transconductance: 8000 µmhos
• Plate Current: 10 mA
• Grid-No. 2 Current: 1.5 mA
• Grid-No. 1 Voltage (Approximate for plate current of 20 µA): -6 V

Maximum Ratings

The maximum ratings are established under the Design-Maximum system for Class A1 amplifier operation of each unit:

• Plate Voltage: 250 V maximum
• Grid-No. 2 (Screen-Grid) Supply Voltage: 180 V maximum
• Grid-No. 2 Voltage: Subject to specific rating curves
• Cathode Current: 20 mA maximum
• Plate Dissipation (Either plate individually): 1.5 W maximum
• Plate Dissipation (Both plates, both units operating): 2.5 W maximum
• Grid-No. 2 Input (for Grid-No. 2 voltages up to 90 V): 0.5 W maximum
• Grid-No. 2 Input (for Grid-No. 2 voltages between 90 V and 180 V): Subject to specific rating curves

Technical Summary

The 17C9 is a miniature, sharp-cutoff dual tetrode designed for VHF RF-amplifier and autodyne mixer applications. It features a 16.8 V, 0.15 A heater and requires a specialized 10-contact socket. With an internal shield and low unit-to-unit capacitances, it provides excellent isolation between its two independent tetrode sections. Each unit offers a transconductance of 8000 µmhos and a plate resistance of approximately 0.1 MΩ under typical Class A1 operating conditions. The design-maximum ratings allow a plate voltage of up to 250 V and a combined plate dissipation of 2.5 W when both units are operating.