0Z4A — Full-Wave Gas Rectifier Tube

Overview

The 0Z4A (also designated as 0Z4A/1003 or 0Z4A/CK1003) is a gas-filled, full-wave double diode employing an ionic-heated, cold cathode. It is designed primarily for use as a full-wave power rectifier in electronic equipment operating with vibrator-type power supplies. Because it utilizes a cold cathode, the 0Z4A requires no heater or filament voltage, eliminating the power consumption and circuitry associated with a heater supply.

The 0Z4A represents an upgraded version of the standard 0Z4 and 0Z4G rectifiers, offering higher peak plate current, increased maximum DC output current, and improved output voltage characteristics under typical operating conditions. Like other power-handling tubes, the 0Z4A requires adequate ventilation during operation to ensure reliable performance.

Mechanical Design, Cold Cathode, and Physical Dimensions

The 0Z4A is constructed with a metal envelope (MT-8 Metal) and a small wafer octal base. The tube is designed to be mounted in any position.

The physical dimensions of the 0Z4A are as follows:

• Maximum Overall Height: 2-5/8 inches (2.625 inches)
• Maximum Seated Height: 2.063 inches
• Maximum Diameter: 1-5/16 inches (1.3125 inches) or 1.031 inches depending on the specific manufacturing outline
• Envelope Body Height: 2-1/16 inches maximum

Because the cathode is ionic-heated, the tube does not contain a filament or heater. The cathode is heated solely by the ionic bombardment resulting from the gas discharge within the tube during conduction. This cold-cathode construction means that the tube remains completely inactive until the applied plate voltage reaches the minimum starting threshold.

Basing and Terminal Connections

The 0Z4A utilizes an octal base and is associated with the 4R and 8XA basing configurations. The tube requires a standard octal socket. The terminal connections, viewed from the bottom of the tube, are assigned as follows:

Note: Some technical layouts designate Pin 6 as having no connection, while others designate Pin 7 as having no connection; both configurations maintain compatibility with standard octal sockets.

Electrical Ratings and Operating Limits

The electrical limits of the 0Z4A are defined under the Design-Center Rating System. These ratings establish the maximum and minimum boundaries within which the tube must be operated to prevent damage or premature failure.

The minimum ratings are critical operational constraints:

• Minimum Starting Voltage: An absolute minimum peak starting voltage of 300 V per plate is required to initiate the gas discharge and establish conduction. Under no circumstances should the starting voltage fall below this value.
• Minimum DC Output Current: The tube must not be operated with less than 30 mA of cathode current. Operating below this minimum threshold fails to maintain the ionic heating of the cathode, which can cause the gas discharge to extinguish or become unstable.
• Minimum Plate Supply Impedance: A minimum of 300 ohms of total effective plate supply impedance (including the vibrator, transformer, and wiring) must be present in the circuit per plate to limit peak currents and protect the tube from excessive ion bombardment.

Typical Operation and Performance Characteristics

In typical full-wave vibrator-type power supply applications with a capacitor-input filter, the 0Z4A operates under the following conditions:

• Peak Plate Supply Voltage (Per Plate): 440 Volts (measured as the open-circuit voltage on the flat portion of the transformer voltage wave)
• Filter-Input Capacitor: 8 µF
• Total Effective Plate Supply Impedance (Per Plate): 600 Ohms (including the vibrator, transformer, and wiring)
• DC Output Current: 100 mA to 110 mA
• DC Output Voltage: 310 Volts (at the input to the filter)
• Average Dynamic Voltage Drop: 24 Volts (measured per plate at a current of 110 mA)

The low average dynamic voltage drop of 24 V is a characteristic of gas-filled rectifiers, providing high efficiency and relatively stable voltage regulation compared to high-vacuum rectifiers.

Comparison with Related Designations

The 0Z4A is part of a family of cold-cathode gas rectifiers that includes the standard 0Z4 and the glass-envelope 0Z4G. While they share the same basic operating principles and basing configurations, the 0Z4A features significantly higher performance ratings:

• Envelope Material: The 0Z4 and 0Z4A utilize a metal MT8 envelope, whereas the 0Z4G is housed in a glass T-7 envelope.
• Current Handling: The 0Z4A supports a maximum peak plate current of 330 mA and a maximum DC output current of 110 mA, compared to 270 mA peak plate current and 90 mA maximum DC output current for the standard 0Z4 and 0Z4G.
• Typical Output: Under typical operating conditions, the 0Z4A delivers a DC output of 310 V at 100–110 mA (with a 600-ohm plate supply impedance), whereas the 0Z4 and 0Z4G typically deliver 275 V at 65 mA (with an 800-ohm plate supply impedance).
• Voltage Drop Reference: The 24-volt tube drop is achieved at a full 110 mA plate current in the 0Z4A, whereas the standard 0Z4 and 0Z4G exhibit the same 24-volt drop at a lower plate current of 90 mA.

Technical Summary

The 0Z4A is an octal-based, cold-cathode, gas-filled double diode designed for full-wave rectification in vibrator-type power supplies. By utilizing an ionic-heated cathode, it eliminates the need for a heater supply, making it highly efficient for mobile or portable equipment. The tube features a maximum peak inverse voltage of 880 V, a maximum peak plate current of 330 mA, and a maximum DC output current of 110 mA. To ensure stable gas conduction, the circuit must maintain a minimum starting voltage of 300 V per plate, a minimum DC output current of 30 mA, and a minimum plate supply impedance of 300 ohms.