17Y9 — Double Dissimilar Pentode

A miniature, double dissimilar pentode designed for television receiver applications, combining a high-transconductance video output pentode and a versatile signal pentode in a single envelope.

Overview

The 17Y9 is a miniature, double dissimilar pentode designed primarily for use in color television receivers. It combines two distinct pentode units with different electrical characteristics in a single envelope. Unit 1 is optimized as a high-transconductance video output pentode, while Unit 2 is designed for service as a sound intermediate-frequency (IF) amplifier, automatic gain control (AGC) amplifier, or sync separator.

The 17Y9 is electrically identical to the 6Y9/EFL200 except for its heater ratings, which are configured for series-string television receiver designs.

Heater and Physical Construction

The 17Y9 features an indirectly heated cathode system. The heater is designed for series-string operation with a nominal current of 0.3 A (300 mA). Depending on the rating system applied, the nominal heater voltage is specified as either 16.5 V or 17.0 V.

The tube is constructed in a miniature T-6 1/2 glass envelope. It utilizes a 10-pin base (basing configuration 10L) and requires a specialized miniature 10-contact socket. The physical dimensions are:

• Maximum Diameter: 0.875 inches
• Maximum Seated Height: 2.625 inches
• Maximum Overall Height: 2.875 inches

Heater-to-Cathode Voltage Ratings

The insulation between the heater and the cathodes is rated to withstand significant potential differences, which is critical in series-string heater chains:

• Heater Negative with Respect to Cathode: 200 V (Total DC and Peak)
• Heater Positive with Respect to Cathode (DC): 100 V
• Heater Positive with Respect to Cathode (Total DC and Peak): 200 V
• Peak Heater-Cathode Voltage (General): ±200 V

Pinout and Electrode Connections

The 10L basing arrangement provides separate connections for the control grids, screen grids, and plates of both units. Unit 1 features an internal shield connected to its cathode and suppressor grid (Grid No. 3). Unit 2 has its cathode and suppressor grid tied to a single pin.

Electrical Characteristics and Typical Operation

The two pentode units in the 17Y9 are highly dissimilar, tailored to their respective roles in television circuitry. Unit 1 is a high-slope, low-resistance power pentode, whereas Unit 2 is a high-resistance, medium-slope signal pentode.

The typical Class A1 amplifier characteristics for each unit are as follows:

Maximum Ratings

The maximum ratings for the 17Y9 are documented under both the Design-Maximum system and the Absolute Maximum system. Designers must adhere to these limits to ensure reliable operation.

Design-Maximum Ratings

Under the Design-Maximum system, the limits are:

Absolute Maximum Ratings

Under the Absolute Maximum system, the limits are:

Circuit-Specific Operating Examples

The 17Y9's dual-unit architecture allows it to perform multiple roles in a television chassis. The following examples illustrate typical operating conditions for various circuit configurations.

Unit 1 — Video Output Amplifier

Unit 1 is designed to deliver high peak-to-peak output voltages into a video load. The following table outlines five typical operating points:

Unit 2 — Sync Separator

When configured as a sync separator, Unit 2 operates with low plate current and reduced transconductance:

Unit 2 — AGC Amplifier

In automatic gain control (AGC) amplifier service, Unit 2 operates under the following typical conditions:

• Plate Voltage: 100–150 V
• Grid No. 2 Voltage: 60 V
• Grid No. 1 Voltage: -1.3 V
• Plate Current: 1.0 mA
• Transconductance: 2,500 µmhos

Unit 2 — IF Amplifier

When used as a sound intermediate-frequency (IF) amplifier, Unit 2 provides high gain:

Interelectrode and Inter-Unit Capacitances

Because the 17Y9 houses two high-gain pentodes in a single envelope, minimizing capacitive coupling between the units is critical for stable operation. The direct interelectrode capacitances, measured without an external shield, are detailed below:

Unit 1 Capacitances

• Plate to All Other Elements (except Grid No. 1): 7 pF
• Grid No. 1 to All Other Elements (except Plate): 12 pF
• Plate to Grid No. 1: 0.095 pF

Unit 2 Capacitances

• Plate to All Other Elements (except Grid No. 1): 11 pF
• Grid No. 1 to All Other Elements (except Plate): 10 pF
• Plate to Grid No. 1: 0.140 pF
• Grid No. 1 to Heater: 0.100 pF (or <0.100 pF)

Inter-Unit Capacitances

• Plate to Plate: 0.150 pF (or <0.150 pF)
• Grid to Grid: 0.010 pF (or <0.010 pF)
• Plate (Unit 1) to Grid No. 1 (Unit 2): 0.100 pF (or <0.100 pF)
• Plate (Unit 2) to Grid No. 1 (Unit 1): 0.005 pF (or <0.005 pF)

Technical Summary

The 17Y9 is a highly specialized double dissimilar pentode designed for television receiver applications. It features a 16.5 V / 17.0 V, 0.3 A heater suitable for series-string power supplies, housed in a T-6 1/2 miniature envelope with a 10-pin base (10L).

Unit 1 serves as a high-transconductance (21,000 µmhos) video output pentode capable of dissipating up to 5.8 W (absolute maximum) and delivering large peak-to-peak output swings. Unit 2 is a versatile signal pentode with a transconductance of 8,500 µmhos and a plate dissipation rating of up to 1.75 W (absolute maximum), making it ideal for IF amplification, AGC amplification, or sync separation.

With its low inter-unit capacitances and independent electrode connections, the 17Y9 provides a compact, dual-stage solution that reduces component count and chassis space in television designs.