10GV8 — High-Mu Triode-Power Pentode Vacuum Tube

An indirectly heated, multi-unit miniature valve combining a high-mu triode and a power pentode in a single envelope, designed for sync-amplifier and video-output applications in television receivers.

Overview

The 10GV8 (also designated as 10GV8/LCL85) is a multi-unit miniature vacuum tube containing a high-mu triode and a power pentode within a single glass envelope. It is designed primarily for specialized television receiver applications, specifically serving as a sync-amplifier and video-output amplifier. The tube features a miniature 9-pin construction and requires a standard miniature 9-contact socket.

The 10GV8 belongs to a family of identical-structure tubes that share the same internal electrode configurations, physical dimensions, and electrical characteristics, differing only in their heater ratings and heater-cathode voltage limits. This family includes the 6GV8/ECL85, 9GV8/XCL85, and 18GV8/PCL85.

Construction, Heater, and Basing

The 10GV8 is constructed in a miniature glass envelope utilizing the 6G outline designation. It features separate, indirectly heated cathodes for the triode and pentode sections, allowing independent biasing and circuit configurations. The pentode section includes an internally connected suppressor grid (Grid No. 3) tied directly to its cathode.

Heater Specifications

The heater of the 10GV8 is designed for series or parallel AC/DC operation. The electrical specifications for the 10GV8 heater, compared alongside its sister designations, are detailed below:

Pinout and Basing Diagram

The tube utilizes the 9LY basing arrangement, which provides independent connections for almost all electrodes, ensuring minimal interaction between the high-gain triode and the power pentode sections:

• Pin 1: Triode Plate ($P_T$)
• Pin 2: Triode Grid ($G_T$)
• Pin 3: Triode Cathode ($K_T$)
• Pin 4: Heater (H)
• Pin 5: Heater (H)
• Pin 6: Pentode Cathode / Grid No. 3 ($K_P$, $G_{3P}$)
• Pin 7: Pentode Grid No. 1 ($G_{1P}$)
• Pin 8: Pentode Grid No. 2 / Screen Grid ($G_{2P}$)
• Pin 9: Pentode Plate ($P_P$)

Absolute Maximum Ratings

The absolute maximum ratings define the limiting operating conditions beyond which the serviceability and safety of the tube may be severely impaired. The triode and pentode units have distinct power and voltage capabilities:

\u002a Maximum pulse duration of 5 percent of a cycle, with a absolute maximum limit of 1 millisecond.

\u2020 This peak value must be measured using a recurrent waveform method to ensure that the average and plate dissipation ratings of the tube are not exceeded.

\u2021 Maximum pulse duration of 200 microseconds. If a larger flyback pulse is required in the circuit, this peak limit must be reduced to 100 mA with a maximum pulse duration of 400 microseconds.

Electrical Characteristics and Operating Points

The 10GV8 offers distinct electrical profiles for its triode and pentode sections under Class A amplifier conditions. The pentode section is characterized at both standard DC operating points and high-current pulsed points.

Triode Unit Characteristics

At a typical operating point, the triode unit exhibits high voltage amplification capabilities:

• Plate Voltage: 100 V
• Grid-No. 1 Voltage: -0.8 V
• Amplification Factor (\u03bc): 50
• Plate Resistance (Approx.): 7,600 \u03a9
• Transconductance ($g_m$): 6,500 \u03bcmhos
• Plate Current: 5 mA

Pentode Unit Characteristics

The pentode unit is characterized under three distinct operating conditions. The first two represent low-voltage, high-current peak states measured via recurrent waveforms, while the third represents a standard Class A operating point:

Circuit Design and Maximum Values

To prevent thermal runaway and maintain bias stability, specific limits are placed on the control grid (Grid-No. 1) circuit resistance. These values depend on the chosen biasing method:

• Triode Unit Grid-No. 1 Circuit Resistance:
  • Fixed-bias operation: 1.0 M\u03a9 max
  • Cathode-bias operation: 3.3 M\u03a9 max
• Pentode Unit Grid-No. 1 Circuit Resistance:
  • Fixed-bias operation: 1.0 M\u03a9 max
  • Cathode-bias operation: 2.2 M\u03a9 max

Technical Summary

The 10GV8 is a highly specialized high-mu triode-power pentode designed for television receiver circuitry. Operating with an 11.6 V / 0.45 A heater, it provides a compact, single-envelope solution for sync-amplifier and video-output stages. The triode section delivers a high amplification factor of 50 with a transconductance of 6,500 \u03bcmhos, while the robust pentode section is capable of handling up to 7 W of plate dissipation and peak plate pulses up to 2,000 V. By adhering to the specified grid resistance limits and pulse duty-cycle restrictions, designers can reliably utilize the 10GV8 in demanding television deflection and signal-processing environments.