19X3 — Half-Wave High-Vacuum Rectifier and Booster Diode

The 19X3 (also written as 19 X 3) is a half-wave high-vacuum rectifier and booster diode designed specifically for television damper service. Introduced by N.V. Philips' Gloeilampenfabrieken under RTMA release #1029 on October 16, 1951, the 19X3 features a coated unipotential cathode and is housed in a T6 1/2 glass envelope with a small button noval 9-pin base.

Physical Specifications and Basing

The 19X3 is designed for flexible installation and can be mounted in any position. Its physical dimensions and mechanical characteristics are as follows:

• Bulb Type: T6 1/2
• Outline Drawing: 6-4
• Maximum Overall Length: 3 1/16 inches
• Maximum Seated Height: 2 13/16 inches
• Bulb Length (excluding tip): 2 7/16 inches ± 3/32 inch
• Maximum Diameter: 7/8 inch
• Basing Designation (JETEC): 9BM

The tube utilizes a 9-pin miniature (noval) base. The pinout configuration is defined as:

Heater and Electrical Characteristics

The 19X3 is equipped with an indirectly heated, coated unipotential cathode. Its heater and basic electrical parameters include:

• Heater Voltage: 19 V
• Heater Current: 0.3 A (300 mA)
• Interelectrode Capacitance (Plate to Cathode, $C_{p-k}$): 5.5 µµF
• Tube Voltage Drop: 16 V at 180 mA D-C

Television Damper Service Ratings

In television damper service, the 19X3 operates under demanding high-voltage pulse conditions. The maximum ratings established for this service are:

• Maximum Peak Inverse Plate Voltage: 4,000 V (subject to pulse duration limits)
• Maximum Peak Plate Current: 400 mA
• Maximum Average Plate Current (D-C Output): 180 mA
• Pulse Duration Limit: The voltage pulse duration must not exceed 18% of one scanning cycle, and must be limited to a maximum of 18 microseconds.

Heater-Cathode Voltage Limits

Because the cathode is subjected to high-voltage pulses in booster service, the insulation between the heater and cathode is rated for the following maximum limits:

• Peak (Cathode Positive with respect to Heater): 650 V
• D.C. Component: 450 V
• A.C. Component: 160 V

Installation and Socketing Requirements

To ensure safe operation and prevent electrical breakdown under high peak inverse voltages, the following installation guidelines must be observed:

• Insulation: Adequate socket insulation is essential to withstand the peak inverse voltage of up to 4,000 V.
• Shielding: For noval 9-pin sockets equipped with a cylindrical center shield, the shield must be removed.
• Flash-over Prevention: It is recommended to physically remove the socket contact for Pin 6 to minimize leakage and the risk of high-voltage flash-over.
• Mounting Plate: For certain socket types, mounting the socket in an insulating plate with a minimum diameter of 1 5/8 inches may be required.
• Unused Pins: Pins 1, 2, 6, 7, and 8 are internally connected (i.c.) and must not be connected externally or used as tie points.

Plate D.C. Characteristics

The plate direct-current characteristic of the 19X3 exhibits a smooth, upward-curving diode response. Typical operating points along this curve are:

• At a plate voltage ($V_p$) of 10 V, the plate current ($I_p$) is approximately 100 mA.
• At a plate voltage ($V_p$) of 20 V, the plate current ($I_p$) is approximately 250 mA.
• At a plate voltage ($V_p$) of 30 V, the plate current ($I_p$) is approximately 440 mA.
• The characteristic curve reaches a plate current of 500 mA at approximately 33 V.

Technical Summary

The 19X3 is a 9-pin miniature (noval) booster diode and half-wave high-vacuum rectifier designed for television damper service. Operating with a 19 V, 0.3 A heater, it provides a low voltage drop of 16 V at 180 mA D-C. It is rated for a maximum peak inverse voltage of 4,000 V and a peak plate current of 400 mA, subject to strict pulse duration limits (maximum 18% of a cycle or 18 microseconds). Proper installation requires removing cylindrical center shields, ensuring robust socket insulation, and avoiding any external connections to the internally connected pins (Pins 1, 2, 6, 7, and 8) to prevent flash-over and leakage.