17KV6 — Beam Power Tube
The 17KV6 is a Novar-type beam power tube designed primarily for high-voltage pulse- or shunt-regulator applications in color television receivers.
Overview
The 17KV6 is a specialized beam power tube constructed in a Novar envelope. It is designed to handle high-voltage pulses and serve as a shunt regulator in color television receivers, specifically within 525-line, 30-frame scanning systems.
Electrically, the 17KV6 is identical to the 6KV6 except for its heater characteristics and ratings. It features a robust cathode structure, high peak current capabilities, and high-voltage insulation to withstand the demanding conditions of television deflection and regulation circuitry.
Construction, Heater, and Physical Characteristics
The 17KV6 is housed in a glass envelope conforming to outline section 31D. It utilizes a 9-contact Novar base, which requires a specialized Novar socket. The physical design is optimized to manage high thermal loads, with a maximum allowable bulb temperature of 240 °C at its hottest point.
The tube features an indirectly heated cathode with a controlled warm-up time, making it suitable for series-string heater arrangements.
Pinout and Base Connections
The 17KV6 utilizes the 9QU pin terminal diagram. The 9-pin Novar base provides separate connections for the internal electrodes, including dual connections for Grid No. 2 to assist in heat dissipation and low-impedance RF grounding.
The pin assignments, viewed from the bottom of the tube base, are as follows:
Electrical Characteristics and Class A1 Operation
The 17KV6 can be operated as a Class A1 amplifier. The tube's characteristics vary significantly depending on the applied electrode potentials. Two distinct operating points illustrate its behavior under static and pulsed conditions:
Operating Point A (Zero-Bias, Pulsed Measurement)
This point represents a high-current state measured via a recurrent waveform to prevent thermal damage:
- Plate Voltage: 100 V
- Grid-No. 3 Voltage: 0 V
- Grid-No. 2 Voltage: 140 V
- Grid-No. 1 Voltage: 0 V
- Plate Current: 580 mA
- Grid-No. 2 Current: 24 mA
Operating Point B (Typical Static Bias)
This point represents a typical biased operating condition:
- Plate Voltage: 140 V
- Grid-No. 3 Voltage: 0 V
- Grid-No. 2 Voltage: 140 V
- Grid-No. 1 Voltage: -24.6 V
- Plate Current: 80 mA
- Grid-No. 2 Current: 2.4 mA
- Plate Resistance (Approximate): 6,000 Ω
- Transconductance: 9,500 µmhos
- Triode Amplification Factor: 4 (measured with Grid No. 3 connected to cathode, and Grid No. 2 connected to plate at the socket)
- Grid-No. 1 Cutoff Voltage: -42 V (for a plate current of 1 mA)
High-Voltage Pulse and Shunt Regulator Service
The primary application of the 17KV6 is as a high-voltage pulse or shunt regulator in television receivers. Under these conditions, the tube is subjected to extreme peak voltages and must be operated within strict design-maximum ratings to ensure reliability.
Design-Maximum Ratings (525-Line, 30-Frame System)
- DC Plate Supply Voltage (at zero plate current): 770 V
- Peak Positive-Pulse Plate Voltage: 6,500 V (for a pulse duration not exceeding 15% of a horizontal scanning cycle, or a maximum of 10 µs)
- Peak Negative-Pulse Plate Voltage: 1,500 V
- DC Grid-No. 3 Voltage: 75 V
- DC Grid-No. 2 Voltage: 220 V
- DC Grid-No. 1 Voltage (Negative-bias value): 75 V
- Peak Negative-Pulse Grid-No. 1 Voltage: 330 V
- Peak Cathode Current: 950 mA
- Average Cathode Current: 275 mA
- Grid-No. 2 Input Power: 3.5 W
- Plate Dissipation: 20 W continuous (up to 24 W is temporarily permissible for a maximum duration of 10 seconds, provided the maximum envelope temperature is not exceeded and adequate circuit precautions are implemented to protect the tube in the event of a loss of Grid-No. 1 bias)
Maximum Circuit Values
- Grid-No. 1-Circuit Resistance: 1.0 MΩ (for grid-No. 1-resistor-bias operation)
Interelectrode Capacitances
The direct interelectrode capacitances of the 17KV6, measured without an external shield, are approximately:
- Grid No. 1 to Plate: 1.2 pF
- Input Capacitance (Grid No. 1 to Cathode, Heater, Grid No. 2, and Grid No. 3): 22 pF
- Output Capacitance (Plate to Cathode, Heater, Grid No. 2, and Grid No. 3): 9 pF
These capacitances reflect the physical geometry of the beam power structure, where the screen grid (Grid No. 2) and beam-forming plates (Grid No. 3) provide electrostatic shielding between the control grid and the plate, keeping the direct grid-to-plate capacitance relatively low.
Technical Summary
The 17KV6 is a high-performance, Novar-based beam power tube designed for demanding high-voltage shunt regulator and pulse applications. Operating with a 16.8 V, 0.6 A heater, it is optimized for series-string television chassis. The tube is characterized by its ability to withstand peak positive plate pulses up to 6,500 V and peak cathode currents up to 950 mA. With a continuous plate dissipation rating of 20 W (extendable to 24 W under transient conditions) and a robust transconductance of 9,500 µmhos at typical operating points, the 17KV6 provides the high-current capability and voltage tolerance required for stable high-voltage regulation in color television systems.
