10DE7 — Dissimilar Double Triode Vacuum Tube

An indirectly heated, miniature dual-section tube designed as a combined vertical-deflection oscillator and vertical-deflection amplifier in television receivers.

Overview

The 10DE7 is a miniature, dissimilar double triode containing two electrically independent and highly distinct triode sections within a single T-6 1/2 glass envelope. The two sections are optimized for entirely different roles in television deflection circuits:

• Unit No. 1 is a medium-mu triode designed to operate as a blocking oscillator in vertical-deflection circuits.
• Unit No. 2 is a low-mu, high-current triode designed to operate as a vertical-deflection amplifier.

The tube features a 9-pin miniature button base and an indirectly heated cathode system. Its heater is specifically designed for series-string television receivers, incorporating controlled warm-up characteristics to minimize voltage surges during start-up.

Physical Construction, Base, and Pinout

The 10DE7 is housed in a standard T-6 1/2 glass bulb. It utilizes a 9-pin miniature button base (designated E9-1) with a 9HF basing arrangement. The physical dimensions of the tube are as follows:

• Maximum overall height: 2.625 inches (2 5/8")
• Maximum seated height: 2.375 inches (2 3/8")
• Maximum diameter: 0.875 inches (7/8")

The tube can be mounted and operated in any position.

The pin connections, viewed from the bottom of the base, are assigned as follows:

• Pin 1: Plate (Unit No. 2)
• Pin 2: Grid (Unit No. 2)
• Pin 3: Grid (Unit No. 2)
• Pin 4: Heater
• Pin 5: Heater
• Pin 6: Plate (Unit No. 1)
• Pin 7: Grid (Unit No. 1)
• Pin 8: Cathode (Unit No. 1)
• Pin 9: Cathode (Unit No. 2)

The double connection to the grid of Unit No. 2 (Pins 2 and 3) helps reduce input impedance and provides flexibility in circuit layout.

Heater Characteristics and Thermal Control

The 10DE7 heater is designed for series-string operation in television receivers. It has controlled thermal characteristics to ensure that heater voltage surges during the warm-up cycle are minimized, provided it is operated in series with other heaters having similar controlled warm-up characteristics.

Heater-Cathode Voltage Ratings

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

• Heater negative with respect to cathode: 200 V (total DC and peak)
• Heater positive with respect to cathode: 100 V DC, with a maximum total DC and peak limit of 200 V

Electrical Characteristics and Class A Operation

Because the 10DE7 is a dissimilar double triode, the two sections exhibit highly contrasting electrical characteristics. Unit No. 1 is optimized for voltage amplification and oscillation, whereas Unit No. 2 is optimized for power amplification.

The typical Class A1 amplifier characteristics for each section are:

The relationship between transconductance, plate resistance, and amplification factor can be verified via calculation.

Calculation for Unit No. 1: $\mu \approx g_m \times r_p = 0.002\text{ S} \times 8,750\ \Omega = 17.5$

Calculation for Unit No. 2: $\mu \approx g_m \times r_p = 0.0065\text{ S} \times 925\ \Omega = 6.01$

These calculations align precisely with the published nominal amplification factors.

Vertical-Deflection Service and Maximum Ratings

The primary application of the 10DE7 is in television receivers operating under a 525-line, 30-frame system. In this service, Unit No. 1 operates as a vertical-deflection blocking oscillator, and Unit No. 2 operates as a vertical-deflection amplifier.

The maximum ratings are defined under the Design-Maximum (or Design-Center) rating systems:

Pulse and Bias Constraints

• Pulse Duration: For vertical-deflection service, the peak pulse ratings are valid only if the pulse duration does not exceed 15% of a vertical scanning cycle, which equates to a maximum of 2.5 milliseconds.
• Grid-Leak Bias Protection: When operating a stage with grid-leak bias, an adequate cathode-bias resistor or other protective means must be incorporated to safeguard the tube against excessive current in the event that excitation is lost.

Interelectrode Capacitances

The direct interelectrode capacitances of the 10DE7 are measured without an external shield. The approximate values for each section are:

The higher capacitances of Unit No. 2 reflect its larger physical electrode structure, which is necessary to support its higher current and power dissipation capabilities.

Average Plate Characteristics and Curve Interpretation

The average plate characteristics of the two sections highlight their distinct design goals:

• Unit No. 1 (Oscillator Section): The plate curves show a family of grid bias lines from $E_{[c1](/tubes/C1)} = 0\text{ V}$ down to $-20\text{ V}$. At a plate voltage of 250 V, the plate current varies smoothly from approximately 25 mA at zero bias down to zero near $-20\text{ V}$. The relatively high plate resistance is indicated by the moderate slope of the plate current lines.
• Unit No. 2 (Amplifier Section): The plate curves for this section exhibit much steeper slopes, reflecting its low plate resistance (925 \Omega). The grid bias lines span from $E_{[c1](/tubes/C1)} = 0\text{ V}$ down to $-60\text{ V}$. At a plate voltage of 150 V, the plate current can exceed 100 mA at low bias levels, demonstrating the high peak-current capability required to drive vertical-deflection coils.

Related Designations and Heater Variants

The 10DE7 belongs to a family of identical dissimilar double triodes that differ only in their heater ratings. These variants are designed to accommodate different power supply configurations:

• 6DE7: Designed for parallel heater circuits, requiring a heater voltage of 6.3 V at a current of 0.9 A (900 mA).
• 13DE7: Designed for series-string circuits, requiring a heater voltage of 13.0 V at a current of 0.45 A (450 mA), with an 11-second warm-up time.
• 19DE7: Designed for series-string circuits, requiring a heater voltage of 19.4 V at a current of 0.3 A (300 mA), with an 11-second warm-up time.

While these tubes share identical internal structures, electrical characteristics, and pinouts, they are not direct plug-in substitutions for one another unless the heater supply circuit is modified to match the specific heater voltage and current requirements.

Technical Summary

The 10DE7 is a versatile, 9-pin miniature dissimilar double triode designed for television vertical-deflection systems. It integrates a medium-mu oscillator (Unit No. 1) and a low-mu, high-current power amplifier (Unit No. 2) in a single T-6 1/2 glass envelope. With a 9.7 V, 0.6 A heater featuring controlled warm-up characteristics, it is optimized for series-string television receivers. By providing two highly specialized triode units with separate cathodes, the 10DE7 delivers an efficient, space-saving solution for generating and amplifying vertical-deflection signals.