10GF7 — Double Dissimilar Triode Vacuum Tube

An indirectly heated, double dissimilar triode of the Novar type, designed for vertical-deflection oscillator and amplifier applications in color television receivers.

Overview

The 10GF7 is a Novar-type double dissimilar triode containing two electrically independent, highly distinct triode sections within a single glass envelope. Section 1 is a high-mu triode intended for vertical-deflection oscillator service, while Section 2 is a low-mu, high-perveance triode designed for vertical-deflection amplifier service.

The tube features a nominal 9.7 V, 0.6 A heater with a controlled warm-up time for use in series-heater strings. The 10GF7A is a subsequent variant that is electrically identical to the 10GF7 but features a shorter bulb and a modified base with an exhaust tip.

Construction, Physical Dimensions, and Shorter "A" Variant

The 10GF7 and 10GF7A are constructed in a T-9 glass envelope using a 9-pin Novar button base. The physical dimensions and base designations differ between the original and the "A" suffix versions:

The 10GF7A is identical to the 10GF7 in all electrical characteristics, ratings, and pin connections, differing only in its shorter bulb and the presence of an exhaust tip on the base (E9-89 base configuration).

Heater and Basing Configuration

The 10GF7 and 10GF7A are designed for series-string heater applications. The heater has a controlled warm-up time to ensure reliable operation in series circuits.

Heater-Cathode Voltage Ratings

To prevent insulation breakdown between the heater and the independent cathodes, the following maximum voltage limits must be observed:

• Heater Negative with Respect to Cathode:
  • Total DC and Peak: 200 Volts
• Heater Positive with Respect to Cathode:
  • DC: 100 Volts
  • Total DC and Peak: 200 Volts

Pinout (9QD Basing)

The 9QD basing arrangement provides independent connections for the two triode sections, viewed from the underside of the base:

• Pin 1: Cathode, Section 1 (1K)
• Pin 2: Grid, Section 2 (2G)
• Pin 3: Cathode, Section 2 (2K)
• Pin 4: Heater (H)
• Pin 5: Heater (H)
• Pin 6: Plate, Section 2 (2P)
• Pin 7: No Connection (NC)
• Pin 8: Plate, Section 1 (1P)
• Pin 9: Grid, Section 1 (1G)

Section 1 electrodes connect to Pins 1, 8, and 9, while Section 2 electrodes connect to Pins 2, 3, and 6.

Electrical Characteristics and Typical Operation

The two triode sections of the 10GF7 are highly dissimilar, optimized for their respective roles in vertical deflection circuitry. Section 1 is a high-mu voltage amplifier, whereas Section 2 is a low-mu, high-current power amplifier.

Direct Interelectrode Capacitances (Unshielded)

The internal capacitances of each section, measured without an external shield, are:

Typical Class A Operating Points

The typical operating characteristics for each section are specified at different voltage and bias points:

Mathematical Verification of Triode Parameters

The fundamental triode relationship is defined as: $\mu = g_m \times r_p$

• Section 1 Calculation: $g_m = 1600\ \mu\text{mhos} = 0.0016\text{ S}$ $r_p = 40,000\ \Omega$ $\mu = 0.0016\text{ S} \times 40,000\ \Omega = 64$ This calculated value matches the published amplification factor of 64 exactly.

• Section 2 Calculation: $g_m = 7200\ \mu\text{mhos} = 0.0072\text{ S}$ $r_p = 750\ \Omega$ $\mu = 0.0072\text{ S} \times 750\ \Omega = 5.4$ This calculated value matches the published amplification factor of 5.4 exactly.

Instantaneous Plate Knee Values (Section 2)

For high-swing deflection service, the perveance of Section 2 is characterized at the plate knee:

• Plate Voltage ($E_b$): 60 V
• Grid Voltage ($E_c$): 0 V
• Plate Current ($I_b$): 95 mA

Design Maximum Ratings

The ratings of the 10GF7 are established under the Design Maximum Rating System. Because the two sections perform entirely different functions, their maximum ratings are specified independently:

Rating Conditions and Pulse Limits

1. Pulse Duty Cycle: For operation in a 525-line, 30-frame television system, the duty cycle of the voltage pulse must not exceed 15% of one scanning cycle.
2. Grid-Leak Bias Protection: In stages operating with grid-leak bias, an adequate cathode-bias resistor or other suitable means is required to protect the tube from excessive current in the absence of excitation.

Related Designations and Heater Variations

The 10GF7 and 10GF7A belong to a family of identical double dissimilar triodes that differ only in their heater configurations:

• 6GF7 / 6GF7A: Designed for parallel heater circuits, operating at 6.3 V with a current of 985 mA (warm-up time is not specified).
• 10GF7 / 10GF7A: Designed for series-string heater circuits, operating at 9.7 V with a current of 600 mA and a controlled 11-second warm-up time.
• 13GF7 / 13GF7A: Designed for series-string heater circuits, operating at 13.0 V with a current of 450 mA and a controlled 11-second warm-up time.

Additionally, the 10EM7 is a related dual triode with a high-mu and low-mu unit, sharing the same heater ratings (9.7 V, 600 mA, 11-second warm-up) but representing a different tube design (derived from the 6EM7).

Technical Summary

The 10GF7 and 10GF7A are Novar-type double dissimilar triodes designed for vertical deflection oscillator and amplifier service in color television receivers. Featuring a 9.7 V, 600 mA heater with an 11-second average warm-up time, they are optimized for series-string power supplies.

Section 1 provides a high-mu ($\mu = 64$) oscillator element with a plate dissipation rating of 1.5 W, while Section 2 provides a high-perveance, low-mu ($\mu = 5.4$) power amplifier capable of handling peak positive plate pulses up to 1500 V and dissipating up to 10 W. The "A" variant offers identical electrical performance in a more compact T-9 envelope with a seated height of 2.000 inches and an exhaust tip on the base.