1007 — Full-Wave Gaseous Rectifier

The 1007 is a full-wave gaseous rectifier tube designed for power rectification applications. It is characterized by its highly versatile design, which allows it to operate either as a directly heated (hot-cathode) rectifier or as a cold-cathode rectifier. The tube features an oxide-coated filament and a gaseous atmosphere, and it is housed in a glass envelope with an octal base.

Construction, Physical Dimensions, and Basing

The 1007 is constructed with an oxide-coated filament and two anodes enclosed in a gaseous atmosphere. The tube is housed in an MT-8 glass bulb (also designated as an M.21-0.1 envelope) and utilizes a small wafer octal 5-pin base. Although the base is physically an octal type, three of the standard eight pin positions are omitted, leaving five active pins.

The physical dimensions of the device are as follows:

• Maximum Overall Length: 2 5/8 inches (approximately 66.8 mm, including pins)
• Maximum Seated Height: 2 1/16 inches
• Maximum Diameter: 1 5/16 inches (approximately 33.5 mm)

The basing arrangement is designated as 5AQ-1-0 or 5.0-LA. When looking at the bottom of the base (with the pins facing the observer), the pin connections are assigned as follows:

The tube is designed to be mounted in any position.

Heater and Cathode Modes

The 1007 can be operated in two distinct cathode modes depending on whether the filament is energized:

1. Hot-Cathode (Directly Heated) Mode: The filament is supplied with a nominal voltage of 1.0 V (with an allowable tolerance of ±10%). Under this condition, the nominal heater current is 1.2 A.
   • Filament Power Calculation: Using the nominal voltage and current, the calculated power consumption of the filament is: $\text{Power} = 1.0\text{ V} \times 1.2\text{ A} = 1.2\text{ W}$
2. Cold-Cathode Mode: The filament is left unheated (0 V supply voltage, drawing 0 A of current). In this mode, the tube relies entirely on the gaseous ionization initiated by the anode voltage to establish conduction, functioning as a cold-cathode glow-discharge rectifier.

Electrical Characteristics and Single-Tube Operation

When operating as a single-tube full-wave rectifier with a condenser-input filter (typically utilizing an 8 µF input capacitor), the electrical characteristics of the 1007 depend heavily on the chosen cathode mode.

Hot-Cathode Operation (1.0 V Filament)

When the filament is heated, the tube exhibits a lower starting voltage and is capable of operating down to zero load current:

• Minimum Peak Starting Voltage: 150 V to 170 V is required to initiate conduction.
• Minimum D-C Output Current: 0 mA (no minimum load current is required to maintain conduction).
• Maximum D-C Output Current: 110 mA to 120 mA.
• Maximum Peak Anode Current: 330 mA (with some ratings permitting up to 1.0 A peak).
• Maximum Peak Inverse Voltage: 980 V to 1,080 V.
• Maximum Peak Anode Voltage: 490 V.

Cold-Cathode Operation (0 V Filament)

When operated with an unheated filament, the tube requires a higher voltage to initiate the gas discharge, and a minimum load current must be maintained to prevent the discharge from extinguishing:

• Minimum Peak Starting Voltage: 340 V is required to start conduction.
• Minimum D-C Output Current: 30 mA must be maintained through the tube during operation.
• Maximum D-C Output Current: 110 mA to 120 mA.
• Maximum Peak Anode Current: 330 mA (with some ratings permitting up to 1.0 A peak).
• Maximum Peak Inverse Voltage: 980 V to 1,080 V.
• Maximum Peak Anode Voltage: 490 V.

Internal Voltage Drop

Regardless of the cathode mode, the tube exhibits a low and relatively constant internal voltage drop during conduction, which is characteristic of gaseous rectifiers. The average dynamic voltage drop is 24 V, with a specified maximum internal voltage drop of 35 V.

Parallel Multi-Tube Operation

For applications requiring different current or voltage capabilities, two 1007 tubes can be operated in parallel. In parallel configurations, a balancing network is required to ensure that both tubes ionize and share the load current. This network typically consists of a 1 MΩ resistor connected across the anodes of each tube, along with a series capacitor ($C_1$). The value of $C_1$ and the overall circuit regulation must be carefully selected to guarantee that both tubes start reliably.

The operating parameters for two-tube parallel configurations with a condenser-input filter are defined as follows:

Hot-Cathode Parallel Operation (1.0 V Filament)

• Minimum Peak Starting Voltage: 170 V
• Minimum D-C Output Current: 0 mA per tube
• Maximum D-C Output Current: 85 mA per tube
• Maximum Peak Anode Current: 510 mA per tube
• Maximum Peak Inverse Voltage: 1200 V
• Maximum Peak Anode Voltage: 600 V
• Average Dynamic Voltage Drop: 24 V

Cold-Cathode Parallel Operation (0 V Filament)

• Minimum Peak Starting Voltage: 340 V
• Minimum D-C Output Current: 30 mA per tube (required to maintain conduction in both tubes)
• Maximum D-C Output Current: 85 mA per tube
• Maximum Peak Anode Current: 510 mA per tube
• Maximum Peak Inverse Voltage: 1200 V
• Maximum Peak Anode Voltage: 600 V
• Average Dynamic Voltage Drop: 24 V

Environmental and Temperature Ratings

The 1007 is rated for operation across a wide environmental temperature range. The allowable operating temperature limits for the tube are:

• Minimum Operating Temperature: -55 °C
• Maximum Operating Temperature: +70 °C

These temperature limits ensure reliable gas ionization and stable electrical characteristics under varying environmental conditions.

Technical Summary

The 1007 is an octal-based, full-wave gaseous rectifier tube capable of operating in both directly heated (hot-cathode) and cold-cathode modes. When operated with a 1.0 V, 1.2 A filament supply, it provides a low starting voltage of 150 V to 170 V and can operate down to zero load current. In cold-cathode mode (0 V filament), it eliminates the need for a filament supply but requires a higher starting voltage of 340 V and a minimum load current of 30 mA to maintain conduction.

Depending on the circuit configuration (single-tube or two-tube parallel) and the cathode mode, the tube supports maximum D-C output currents ranging from 85 mA to 120 mA per tube, peak anode currents up to 510 mA (or 1.0 A peak under specific ratings), and peak inverse voltages up to 1200 V. With a low average dynamic voltage drop of 24 V to 35 V and an operating temperature range of -55 °C to +70 °C, the 1007 offers a highly adaptable solution for full-wave power rectification.