19DE7 — Dissimilar Double Triode Vacuum Tube

A miniature, dissimilar double triode designed for television receiver applications, combining a medium-mu oscillator section and a high-dissipation, low-mu power amplifier section in a single envelope.

Overview

The 19DE7 is a miniature double triode of the glass-bulb type, featuring two highly dissimilar triode sections within a single T-6 1/2 envelope. It is specifically designed for service in television receivers, where Section 1 (Triode #1) operates as a medium-mu vertical deflection oscillator, and Section 2 (Triode #2) operates as a low-mu vertical deflection amplifier.

The tube is constructed with coated unipotential cathodes and is designed to be mounted in any position. In terms of electrical characteristics, the 19DE7 is identical to the 6DE7 except for its heater ratings, which are tailored for series-string heater circuits.

Mechanical Specifications and Physical Dimensions

The 19DE7 is housed in a standard T-6 1/2 glass bulb with a miniature button 9-pin base (designated as 9HF or E9-1). The physical dimensions of the tube are documented with slight variations in maximum seated height:

• Maximum Diameter: 7/8 inches (0.875 inches)
• Maximum Overall Length / Height: 2 5/8 inches (2.625 inches)
• Maximum Seated Height: 2 1/8 inches (2.125 inches) to 2.375 inches (2 3/8 inches)
• Mounting Position: Any

Heater Ratings

The heater of the 19DE7 is designed for series-string operation with a controlled warm-up time. The heater-to-cathode insulation is rated to withstand significant potential differences, which is critical in television deflection circuits where the cathode voltage of the vertical amplifier can swing substantially.

Using the nominal heater voltage of 19.4 V and the nominal heater current of 0.30 A, the calculated heater power is 19.4 V * 0.30 A = 5.82 W.

Pinout and Basing Configurations

The 19DE7 utilizes a 9-pin miniature button base (9HF). The technical records document two distinct pinout configurations for this designation. Designers must verify the specific layout of the device in use:

Configuration A

• Pin 1: Plate (Triode #1) [P1]
• Pin 2: Grid (Triode #2) [G2]
• Pin 3: Grid (Triode #2) [G2]
• Pin 4: Heater [H]
• Pin 5: Heater [H]
• Pin 6: Grid (Triode #1) [G1]
• Pin 7: Cathode (Triode #1) [K1]
• Pin 8: Plate (Triode #2) [P2]
• Pin 9: Cathode (Triode #2) [K2]

Configuration B

• Pin 1: Grid (Triode #2) [G2]
• Pin 2: Cathode (Triode #2) [K2]
• Pin 3: Grid (Triode #2) [G2]
• Pin 4: Heater [H]
• Pin 5: Heater [H]
• Pin 6: Plate (Triode #1) [P1]
• Pin 7: Grid (Triode #1) [G1]
• Pin 8: Cathode (Triode #1) [K1]
• Pin 9: Plate (Triode #2) [P2]

In both configurations, the heater connections are assigned to Pins 4 and 5, and the grid of the second triode (G2) is connected to multiple pins (Pins 2 and 3 in Configuration A, or Pins 1 and 3 in Configuration B) to facilitate circuit layout and heat dissipation.

Direct Interelectrode Capacitances

The direct interelectrode capacitances are measured without an external shield. Because the two triode sections are highly dissimilar, their capacitances differ significantly:

Electrical Characteristics and Typical Operating Points

The 19DE7 contains two electrically distinct triode systems. Triode #1 is a medium-mu, high-resistance triode optimized for low-power oscillator service, while Triode #2 is a low-mu, low-resistance power triode optimized for driving the vertical deflection coils.

Typical Class A operating conditions and characteristics for each section are as follows:

Additional Operating Points (Triode #2)

• Plate Current at Ec = -24 V DC: 10 mA
• Instantaneous Zero-Bias Plate Current (Eb = 60 V, Ec = 0): 80 mA

Maximum Ratings

The 19DE7 is rated under the Design-Center and Design-Maximum systems for vertical deflection service. The maximum ratings reflect the distinct roles and power handling capabilities of the two sections.

Special Rating Conditions

• Peak Positive Pulse Plate Voltage (Triode #2): The absolute maximum rating of 1500 V is specified 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 (or one horizontal scanning cycle, depending on the rating standard applied).
• Plate Dissipation Protection: In stages operating with grid leak bias, an adequate cathode bias resistor or other suitable protective means is required to safeguard the tube against excessive dissipation in the event that excitation is lost.

Qualitative Curve Observations

The published characteristic curves for the 19DE7 illustrate the distinct behaviors of the two triode sections:

• Section One (Triode #1) Plate Characteristics: Plotted up to a plate voltage (Eb) of 400 V and a plate current (Ib) of 40 mA. The grid voltage (Ec) curves range from 0 V to -20 V in steps of 2 V, demonstrating a linear and evenly spaced characteristic suitable for stable oscillator operation.
• Section Two (Triode #2) Plate Characteristics: Plotted up to a plate voltage (Eb) of 400 V and a plate current (Ib) of 150 mA. The grid voltage curves range from 0 V to -60 V in steps of 5 V. The curves show high current capability at low plate voltages (e.g., reaching 80 mA at zero bias and 60 V plate potential), which is essential for delivering the high peak currents required by vertical deflection output stages.

Technical Summary

The 19DE7 is a specialized, miniature dissimilar double triode designed for television vertical deflection circuits. It features a 19.4 V, 0.30 A series-string heater with a controlled 11-second warm-up time.

The tube combines a medium-mu oscillator section (Section 1: mu = 17.5, rp approx. 8750 ohms, Pd = 1.5 W) and a low-mu, high-dissipation power amplifier section (Section 2: mu = 6.0, rp approx. 925 ohms, Pd = 7.0 W) in a single 9-pin miniature envelope. This dissimilar design allows a single tube to perform both the timing generation and the power amplification functions of the vertical deflection system, minimizing component count and space in television chassis design.