117Z6GT — High-Vacuum Rectifier and Voltage Doubler

An indirectly heated, dual-section high-vacuum rectifier and voltage doubler designed for transformerless power supply applications operating directly from AC power lines.

Overview

The 117Z6GT (also designated as 117Z6-GT) is an indirectly heated, high-vacuum twin rectifier and voltage doubler tube. It features a heater rated at the full nominal line voltage of 117 volts, allowing the tube to be operated directly from standard AC mains without the need for a power transformer or a series dropping resistor. This design is highly advantageous for compact, lightweight, and cost-effective power supply circuits in radio receivers and electronic instruments.

The tube contains two independent rectifier sections within a single glass envelope. While they share a common heater, their cathodes and plates are electrically isolated from one another and connected to separate base pins. This independent dual-diode construction allows the 117Z6GT to be configured in several ways, including as a half-wave voltage doubler, a full-wave rectifier, or a half-wave rectifier with parallel-connected sections.

Heater and Electrical Characteristics

The heater of the 117Z6GT is designed for direct line-voltage operation. Its primary electrical characteristics and ratings are:

• Heater Voltage: 117 V
• Heater Current: 0.075 A (75 mA)
• Calculated Heater Power: 117 V × 0.075 A = 8.775 W (calculated from nominal ratings)
• Cathode Type: Coated unipotential (indirectly heated)

Under typical operating conditions, the tube exhibits a low internal voltage drop. Specifically, the tube voltage drop is 15.5 V per section when conducting a direct current of 120 mA. This low internal resistance helps maintain efficient power conversion and stable output voltage regulation under load.

Base Configuration and Physical Outline

The 117Z6GT is housed in a glass envelope designated by the 9-11 outline drawing and utilizes an octal base with a 7Q pinout configuration. The 7Q base diagram provides independent connections for the two diode sections, arranged as follows (viewed from the bottom of the base):

This physical layout ensures adequate electrical isolation between the high-voltage plates and cathodes. The independent cathode connections are essential for voltage doubler applications, where the two cathodes must operate at different DC potentials relative to each other and the heater.

Operating Ratings and Rectifier/Doubler Service

The 117Z6GT is rated for service as a rectifier or voltage doubler. To ensure reliable operation and prevent premature tube failure, circuit designs must respect the maximum electrical ratings established for each individual diode section:

In a standard half-wave voltage doubler circuit, the two sections operate in series-like configurations across the AC line to deliver a DC output voltage approximately double the peak value of the input AC voltage. The maximum RMS supply voltage rating of 235 V per plate provides a substantial safety margin when operating from standard 117 V mains. When the two sections are operated in parallel for half-wave rectifier service, the total maximum D-C output current can be calculated as 2 × 60 mA = 120 mA, provided the current is equally shared between the sections.

Technical Comparison with Related 117-Volt Tubes

The 117Z6GT belongs to a family of tubes designed with 117-volt heaters, but it occupies a unique position due to its dual-section rectifier-only construction. Comparing its characteristics with other 117-volt tubes highlights these design differences:

• Heater Current and Power: The 117Z6GT draws 0.075 A, which is higher than the single-section half-wave rectifiers 117Z3 and 117Z4-GT (both drawing 0.04 A), but lower than the multi-unit rectifier/beam power amplifier tubes such as the 117L7/M7-GT, 117N7-GT, and 117P7-GT (all drawing 0.09 A).
• Voltage Drop: The 117Z6GT has a tube voltage drop of 15.5 V at 120 mA per section. In comparison, the single-section 117Z3 and 117Z4-GT exhibit a higher drop of 22.5 V at 180 mA, while the rectifier sections of the 117L7/M7-GT, 117N7-GT, and 117P7-GT have a drop of 16 V at 150 mA.
• Rectifier Capabilities: Unlike the 117Z3 and 117Z4-GT, which are dedicated single-section half-wave rectifiers with a maximum D-C output current of 90 mA and a peak inverse voltage of 330 V or 350 V, the 117Z6GT provides two independent sections. This dual-section design allows for a much higher peak inverse voltage rating of 700 V per section and enables voltage doubling, which is not possible with a single-section rectifier.

Technical Summary

The 117Z6GT is a versatile, high-vacuum rectifier and voltage doubler featuring a 117 V, 0.075 A heater and an octal 7Q base. With its two independent diode sections, it offers a maximum peak inverse voltage of 700 V, a maximum RMS supply voltage of 235 V per plate, and a maximum D-C output current of 60 mA per plate (with a peak current limit of 360 mA per plate). Its low internal voltage drop of 15.5 V at 120 mA per section makes it an efficient choice for transformerless power supplies, voltage doublers, and full-wave rectifiers in line-operated consumer and industrial electronics.