16GY5 — Compactron Beam Power Pentode

The 16GY5 is a compactron beam-power pentode designed specifically for use as a horizontal-deflection amplifier in television receivers. It is part of a family of structurally identical tubes that includes the 6GY5 and 21GY5, differing only in their heater ratings and characteristics. The 16GY5 requires a duodecar 12-contact socket for operation.

Physical and Heater Characteristics

The 16GY5 features a compactron T-12 glass envelope construction with a button 12-pin base (E12-74 designation) and a C1-3 top cap. Its physical dimensions are:

• Maximum Diameter: 1.563 inches
• Maximum Seated Height: 3.250 inches
• Maximum Overall Height: 3.625 inches

The tube utilizes a coated unipotential cathode. The heater is designed for series-string television receiver applications and can be operated on either AC or DC.

The average heater warm-up time of 11 seconds is defined as the time required for the voltage across the heater to reach 80 percent of its nominal (bogey) value when starting from a circuit where four times the bogey heater voltage is applied in series with a resistance equal to three times the bogey heater voltage divided by the bogey heater current.

Heater-Cathode Voltage Ratings

To ensure reliable operation and prevent insulation breakdown, the voltage between the heater and cathode must be kept within the following limits:

• Heater Negative with Respect to Cathode: 200 V maximum (total DC and peak)
• Heater Positive with Respect to Cathode: 100 V maximum DC, 200 V maximum (total DC and peak)

Heater Power Calculation

Using the nominal ratings for the 16GY5 heater:

• Input: Heater Voltage ($V_f$) = 15.8 V, Heater Current ($I_f$) = 0.6 A
• Calculation: 15.8 V × 0.6 A = 9.48 W of nominal heater power.

Pinout and Basing

The 16GY5 utilizes the 12DR duodecar basing arrangement. The connections, viewed from the bottom of the tube, are allocated as follows:

Multiple pins are internally connected to the same electrodes (such as Grid No. 1, Grid No. 2, and the Cathode/Grid No. 3 assembly) to facilitate low-inductance wiring and flexible circuit layouts.

Electrical Characteristics and Operating Points

The 16GY5 exhibits high transconductance and low plate resistance under typical Class A1 amplifier operating conditions.

Direct Interelectrode Capacitances

The unshielded capacitances of the 16GY5 are:

• Grid No. 1 to Plate: 0.7 pF
• Input (g1 to h + k + g3): 22 pF
• Output (p to h + k + g2 + g3): 9 pF

Typical Class A1 Operating Points

The tube can be operated in either a standard pentode configuration or a triode configuration (where Grid No. 2 is tied directly to the plate).

At the instantaneous plate knee point where the plate voltage is 60 V, Grid No. 2 is at 130 V, and Grid No. 1 is at 0 V, the plate current reaches 410 mA, while the Grid No. 2 current is between 24 mA and 26 mA. This high-current capability at low plate voltages is a critical characteristic for horizontal-deflection service.

Horizontal-Deflection Service Ratings

When used as a horizontal-deflection amplifier in a 525-line, 30-frame television system, the 16GY5 must be operated within strict Design-Maximum limits to prevent thermal and electrical breakdown.

Maximum Ratings

• DC Plate Supply Voltage (Boost + DC Power Supply): 770 V
• Peak Positive-Pulse Plate Voltage: 6500 V (The pulse duration must not exceed 15% of one horizontal scanning cycle, equivalent to 10 microseconds)
• Peak Negative-Pulse Plate Voltage: 1500 V
• DC Grid No. 2 (Screen Grid) Voltage: 220 V
• Grid No. 2 Dissipation: 3.5 W
• DC Grid No. 1 (Control Grid) Voltage: -55 V
• Peak Negative-Pulse Grid No. 1 Voltage: 330 V
• Plate Dissipation: 18 W
• Peak Cathode Current: 800 mA
• Average Cathode Current: 230 mA
• Bulb Temperature (at hottest point): 220 °C
• Maximum Grid No. 1 Circuit Resistance: 1.0 Megohm

In stages operating with grid-leak bias, an adequate cathode-bias resistor or other protective means must be employed to safeguard the tube against excessive dissipation in the event that excitation is lost.

Technical Summary

The 16GY5 is a high-performance, duodecar-based compactron beam power pentode optimized for horizontal-deflection amplifier service in television receivers. Featuring a 15.8 V, 0.6 A heater with controlled warm-up characteristics, it is designed for integration into series-string heater circuits. The tube's physical design incorporates a T-12 envelope, a 12DR pinout configuration, and a top-cap plate connection to handle high peak positive-pulse voltages up to 6500 V. With a peak cathode current capability of 800 mA and a plate dissipation rating of 18 W, the 16GY5 delivers the robust current-handling capacity required for demanding television deflection systems.