17CK3 — Half-Wave Vacuum Rectifier

A Novar-type half-wave vacuum rectifier designed for damper service in the horizontal-deflection circuits of television receivers.

Overview

The 17CK3 is a specialized damper heater-cathode diode housed in a T-9 glass envelope with a 9-pin Novar button base. It is primarily employed in the horizontal-deflection circuitry of black-and-white television receivers. The 17CK3 is electrically identical to the 6CK3 except for its heater ratings, which are designed for series-string heater circuits.

Construction, Physical Dimensions, and Basing

The 17CK3 features a T-9 glass bulb construction with an exhaust tip located on the base. It uses a Novar Button 9-Pin base (E9-89) with a 9HP basing diagram.

The physical dimensions of the tube are:

• Maximum Diameter: 1.188 inches
• Maximum Seated Height: 2.625 inches
• Maximum Overall Height: 3.005 inches

Socket Connections and Installation

The tube is designed to be mounted in a Novar 9-contact socket. To ensure reliable operation under high-voltage conditions, specific installation guidelines must be followed:

• Unused Terminals: Pins 1, 3, 6, and 8 must not be used as tie points for any auxiliary wiring.
• Arc-Over Prevention: It is recommended to remove the socket tabs associated with these unused pins to reduce the risk of arc-over and minimize electrical leakage.
• Ventilation and Temperature: The tube requires adequate ventilation during operation. The maximum allowable bulb temperature at its hottest point is 220 °C.

Heater and Cathode Characteristics

The 17CK3 is equipped with an indirectly heated, coated cathode. The heater is designed with a controlled warm-up time to ensure reliable operation in series-connected heater strings.

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the unshielded tube are approximately:

• Plate to Cathode and Heater: 6.5 pF
• Cathode to Plate and Heater: 9.0 pF
• Heater to Cathode: 3.0 pF

Damper Service Ratings and Operating Conditions

The 17CK3 is rated under the Design-Maximum System for operation as a damper tube in a standard 525-line, 30-frame television scanning system. In this service, the tube is subjected to high-voltage pulses during the horizontal retrace period.

Design-Maximum Ratings

These ratings represent the limiting values that should not be exceeded under any normal operating conditions:

• Peak Inverse Plate Voltage: 5200 V (provided the pulse duration does not exceed 15% of one horizontal scanning cycle, or 10 microseconds)
• Peak Plate Current (Steady State): 1200 mA
• Average Plate Current (DC): 250 mA
• Plate Dissipation: 6.5 W

Heater-Cathode Voltage Limits

Because the cathode of a damper tube experiences high pulse voltages relative to ground (and thus relative to the heater), the heater-cathode insulation must withstand severe electrical stress. The design-maximum limits are categorized by polarity:

• Heater Negative with Respect to Cathode:
  • DC Limit: 900 V
  • Total DC and Peak Limit: 5200 V
• Heater Positive with Respect to Cathode:
  • DC Limit: 100 V
  • Total DC and Peak Limit: 300 V

Electrical Characteristics

The forward conduction efficiency of the diode is characterized by its instantaneous tube voltage drop. When conducting a plate current of 350 mA, the instantaneous tube voltage drop is 16 V.

Technical Summary

The 17CK3 is a Novar-base, half-wave vacuum rectifier designed for television damper service. Operating with a 16.8 V, 0.450 A heater, it is electrically identical to the 6CK3 except for its heater ratings. It is capable of handling peak inverse plate voltages up to 5200 V and peak currents up to 1200 mA under pulsed conditions in a 525-line, 30-frame system. Its physical design utilizes a T-9 glass envelope with a 9-pin Novar button base, requiring careful socket wiring and adequate ventilation to maintain the bulb temperature below 220 °C.