17GE5 — Beam Power Pentode

The 17GE5 is a Compactron beam power pentode designed primarily for use as a horizontal-deflection amplifier in television receivers, particularly color television sets. It features a coated unipotential cathode and is electrically identical to the 6GE5 and 12GE5 vacuum tubes, differing only in its heater ratings.

Construction, Physical Dimensions, and Pinout Configurations

The 17GE5 is constructed in a Compactron T-12 glass envelope with a 12-pin button base (E12-74) or duodecar 12-contact socket. The physical dimensions of the tube are as follows:

• Maximum Diameter: 1.563 inches
• Maximum Seated Height: 2.500 inches
• Maximum Overall Height: 2.875 inches
• Outline Designation: 12-56 (Outlines section 15A)

Pinout Variations (Basing Diagram 12BJ)

The technical literature documents three distinct pinout configurations under the 12BJ basing diagram. Designers and technicians must verify the specific pin connections of the physical device being used:

Note: Internal connections (IC) must not be used for circuit tie points.

Heater and Cathode Characteristics

The 17GE5 incorporates an indirectly heated, coated unipotential cathode. The heater is designed for series-string or parallel operation with the following specifications:

• Heater Voltage (AC or DC): 15.8 V or 16.8 V (with 16.8 V specified as the bogey value at 0.45 A)
• Heater Current: 0.45 A (with a tolerance of ±0.03 A)
• Average Heater Warm-up Time: 11 seconds
  • Warm-up measurement condition: The time required for the heater voltage to reach 80% of its bogey value when a voltage equal to four times the bogey voltage (67.2 V) is applied to the heater in series with a resistance equal to three times the bogey voltage divided by the bogey current (112 Ω).
• Heater-Cathode Voltage Limits:
  • Heater Negative with Respect to Cathode: 200 V maximum (total DC and peak)
  • Heater Positive with Respect to Cathode: 100 V DC maximum (or 200 V maximum total DC and peak)

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the 17GE5, measured without an external shield, are:

• Grid No. 1 to Plate: 0.34 pF
• Input (G1 to all other electrodes except Plate): 16 pF
• Output (Plate to all other electrodes except G1): 7 pF

Electrical Characteristics and Class A1 Operation

The 17GE5 can be operated under Class A1 amplifier conditions in either pentode or triode configurations. The typical operating points and characteristics are detailed below:

Pentode Connection Characteristics

• Low-Voltage Knee Point:
  • Plate Voltage: 60 V
  • Grid-No. 2 Voltage: 150 V
  • Grid-No. 1 Voltage: 0 V
  • Plate Current: 345 mA (measured using a recurrent waveform method to prevent exceeding maximum ratings)
  • Grid-No. 2 Current: 27 mA (measured using a recurrent waveform method)
• High-Voltage Point (Condition A):
  • Plate Voltage: 250 V
  • Grid-No. 2 Voltage: 150 V
  • Grid-No. 1 Voltage: -22.5 V to -22.6 V
  • Plate Current: 55 mA to 65 mA
  • Grid-No. 2 Current: 1.8 mA
  • Plate Resistance (Approximate): 18,000 Ω
  • Transconductance: 7,300 µmhos
  • Grid-No. 1 Voltage for Plate Current of 1.0 mA (Approximate): -42 V
• High-Voltage Cutoff Point (Condition B):
  • Plate Voltage: 5,000 V
  • Grid-No. 2 Voltage: 150 V
  • Grid-No. 1 Voltage for Plate Current of 1.0 mA (Approximate): -100 V

Triode Connection Characteristics

When Grid No. 2 is connected directly to the plate, the tube exhibits the following characteristics:

• Plate Voltage: 150 V
• Grid-No. 2 Voltage: 150 V
• Grid-No. 1 Voltage: 0 V or -22.5 V
• Amplification Factor (μ): 4.4

Horizontal-Deflection Service and Ratings

The 17GE5 is rated under the Design-Maximum Rating System for operation in television receivers utilizing a standard 525-line, 30-frame scanning system.

Design-Maximum Ratings

• DC Plate Supply Voltage (Boost + DC Power Supply): 770 V
• Peak Positive-Pulse Plate Voltage: 5,500 V to 6,500 V
  • Duty Cycle Restriction: The pulse duration must not exceed 15% of one horizontal scanning cycle (equivalent to a maximum of 10 µs).
• Peak Negative-Pulse Plate Voltage: 1,500 V
• DC Grid-No. 2 Voltage: 220 V
• Peak Negative-Pulse Grid-No. 1 Voltage: 330 V
• DC Grid-No. 1 Voltage: -55 V
• Peak Cathode Current: 550 mA
• Average Cathode Current: 175 mA
• Plate Dissipation: 17.5 W
• Grid-No. 2 Input / Dissipation: 3.5 W
• Bulb Temperature (at hottest point): 200 °C to 220 °C

Circuit Design Constraints

• Grid-No. 1 Circuit Resistance: 1.0 MΩ maximum.
• Tube Protection: In stages operating with grid-leak bias, an adequate cathode bias resistor or other protective means is required to safeguard the tube against excessive plate dissipation in the absence of drive/excitation.

Technical Summary

The 17GE5 is a high-performance Compactron beam power pentode designed for horizontal-deflection amplifier service in television receivers. It features a 15.8 V / 16.8 V heater drawing 0.45 A, with a controlled 11-second warm-up time. The tube is capable of handling high peak positive-pulse plate voltages up to 6,500 V and peak cathode currents of 550 mA. With a plate dissipation rating of 17.5 W and a transconductance of 7,300 µmhos under typical Class A1 conditions, the 17GE5 provides robust performance in demanding television deflection circuits. It is identical to the 6GE5 and 12GE5 except for its heater characteristics.