17JG6A — Beam Power Pentode

The 17JG6A is a novar-type beam power tube designed primarily for use as a horizontal-deflection amplifier in low-B+ black-and-white television receivers operating under 525-line, 30-frame systems. It is electrically identical to the 6JG6A and 22JG6A except for its heater ratings and characteristics.

Mechanical Construction, Basing, and Pinout

The 17JG6A features a glass T-12 envelope with a button 9-pin (E9-88) base, requiring a standard novar 9-contact socket. The physical dimensions of the tube are as follows:

• Maximum Diameter: 1.563 inches
• Maximum Seated Height: 2.750 inches
• Maximum Overall Height: 3.125 inches

The tube utilizes the 9QU basing diagram. There are minor variations in documentation regarding the assignments of Pin 1 and Pin 2; they are variously listed with Grid No. 1 and Grid No. 2 swapped. The pin connections are defined as:

Heater Ratings and Interelectrode Capacitances

The heater is designed for series or parallel AC/DC operation with the following specifications:

• Heater Voltage: 16.8 V
• Heater Current: 0.6 A (600 mA, with a tolerance of ±0.040 A)
• Average Warm-up Time: 11 seconds

Heater-Cathode Voltage Limits

• Peak Value: ±200 V max
• Heater Negative with Respect to Cathode (Total DC and Peak): 200 V max
• Heater Positive with Respect to Cathode (DC): 100 V max
• Heater Positive with Respect to Cathode (Total DC and Peak): 200 V max
• Average Value: 100 V max

Direct Interelectrode Capacitances (Unshielded)

• Grid No. 1 to Plate: 0.7 pF
• Input (Grid No. 1 to Cathode, Heater, Grid No. 2, and Grid No. 3): 22 pF
• Output (Plate to Cathode, Heater, Grid No. 2, and Grid No. 3): 9 pF (or 9.0 pF)

Electrical Characteristics and Operating Points

The 17JG6A can be operated in either triode or pentode configurations. Under Class A1 amplifier conditions, the typical operating points are:

Triode Connection

When Grid No. 2 is connected to the plate at the socket:

• Plate Voltage: 125 V
• Grid No. 3 (Suppressor Grid): Connected to cathode at socket
• Grid No. 1 (Control Grid) Voltage: -20 V
• Amplification Factor: 4.1

Pentode Connection

• Condition A (Instantaneous Plate Knee Values):
  • Plate Voltage: 50 V
  • Grid No. 3: Connected to cathode at socket
  • Grid No. 2 Voltage: 125 V
  • Grid No. 1 Voltage: 0 V
  • Plate Current: 525 mA (measured via recurrent waveform to avoid exceeding maximum ratings)
  • Grid No. 2 Current: 32 mA (measured via recurrent waveform)
• Condition B (Typical Operation):
  • Plate Voltage: 130 V
  • Grid No. 3: Connected to cathode at socket
  • Grid No. 2 Voltage: 125 V
  • Grid No. 1 Voltage: -20 V
  • Plate Resistance (Approx.): 12,000 Ω
  • Transconductance: 10,000 µmhos
  • Plate Current: 80 mA
  • Grid No. 2 Current: 2.5 mA
  • Grid No. 1 Voltage for Plate Current of 1 mA (or 10 mA in some specifications): approx. -40 V

Horizontal-Deflection Service and Maximum Ratings

For horizontal-deflection amplifier service in a 525-line, 30-frame television system, the 17JG6A is rated under the Design-Maximum Rating System.

Design-Maximum Ratings

• DC Plate Supply Voltage (Boost + DC Power Supply): 770 V max
• Peak Positive-Pulse Plate Voltage: 6500 V max (pulse duration must not exceed 15% of one horizontal scanning cycle, or 10 µs)
• Peak Negative-Pulse Plate Voltage: 1500 V max
• DC Grid-No. 3 Voltage: 75 V max (a positive voltage, typically 30 V, may be applied to reduce "snivets" interference in VHF/UHF receivers)
• DC Grid-No. 2 Voltage: 220 V max
• DC Grid-No. 1 Voltage (Negative-bias value): -55 V max
• Peak Negative-Pulse Grid-No. 1 Voltage: 330 V max
• Peak Cathode Current: 950 mA max
• Average Cathode Current: 275 mA max
• Plate Dissipation: 17 W max (a bias resistor or other protective means is required to protect the tube in the absence of excitation)
• Grid-No. 2 Input (Dissipation): 3.5 W max
• Bulb Temperature (at hottest point): 220 °C to 240 °C max

Maximum Circuit Values

• Grid-No. 1-Circuit Resistance (for grid-No. 1-resistor-bias operation in horizontal deflection): 2.2 MΩ max
• Grid-No. 1-Circuit Resistance (other applications):
  • Fixed-bias operation: 0.25 MΩ max
  • Cathode-bias operation: 1.0 MΩ max

Qualitative Curve Analysis

The average plate characteristics of the 17JG6A are referenced to the type 6JF6.

• Plate Characteristics (Grid No. 3 to Cathode, $E_{c2} = 125\text{ V}$): Plate current ($I_b$) rises rapidly below 50 V plate voltage, leveling off to a flat knee. At $E_{[c1](/tubes/C1)} = 0\text{ V}$, peak plate current reaches approximately 900 mA. Grid-No. 2 current ($I_{c2}$) peaks sharply at low plate voltages (up to ~100 mA at $E_b = 0\text{ V}$) and falls off rapidly as plate voltage increases.
• Plate Characteristics (Grid No. 3 to Cathode, $E_{[c1](/tubes/C1)} = 0\text{ V}$): Plate current curves for various screen voltages ($E_{c2}$ from 50 V to 175 V) show a strong, proportional upward shift in plate current capacity with higher screen voltages, exceeding 1000 mA at $E_{c2} = 175\text{ V}$.

Technical Summary

The 17JG6A is a high-performance, novar-based beam power pentode designed for demanding horizontal-deflection amplifier applications. Featuring a 16.8 V, 0.6 A heater with a controlled 11-second warm-up time, it is optimized for series-string television receivers. The tube is capable of handling peak positive-pulse plate voltages up to 6500 V and peak cathode currents up to 950 mA. With a plate dissipation rating of 17 W and high transconductance of 10,000 µmhos, the 17JG6A provides robust and efficient operation in low-B+ television chassis.