17JQ6 — Beam Power Tube with Integral Diode
The 17JQ6 is a miniature beam power tube featuring an integral diode internally connected to grid No. 3. It is designed primarily for feedback-stabilized vertical-deflection-amplifier applications in color and black-and-white television receivers operating on 525-line, 30-frame scanning systems.
Overview and Family Relationships
The 17JQ6 belongs to a family of electrically similar beam power tubes. It is identical to the 6JQ6, 12JQ6, and 25JQ6 except for its specific heater ratings. The tube's design incorporates an integral diode plate connected internally to the suppressor grid (grid No. 3), making it uniquely suited for specialized vertical-deflection circuitry where feedback stabilization is required.
Construction, Pinout, and Heater Ratings
The 17JQ6 is housed in a miniature glass envelope requiring a standard miniature 9-contact socket. The physical outline corresponds to section 6G, and the electrical connections are defined by the 9RA pinout diagram.
Pin Connection Diagram (9RA)
The nine pins of the base are connected as follows:
- Pin 1: Plate (P)
- Pin 2: Internal Connection (IC) — Do not use
- Pin 3: Grid No. 2 (Screen Grid) (G2)
- Pin 4: Heater (H)
- Pin 5: Heater (H)
- Pin 6: Grid No. 3 and Diode Plate (G3, PD)
- Pin 7: Grid No. 1 (Control Grid) (G1)
- Pin 8: Grid No. 1 (Control Grid) (G1)
- Pin 9: Cathode (K)
Heater Specifications
The heater is designed for operation in series or parallel heater chains:
- Heater Voltage (AC or DC): 16.8 V to 17.0 V
- Heater Current: 0.45 A (with a tolerance of ±0.030 A)
- Average Warm-up Time: 11 seconds
- Heater-Cathode Voltage:
- Peak value: ±200 V maximum
- Average value: 100 V maximum
Direct Interelectrode Capacitances
The direct interelectrode capacitances of the 17JQ6, measured without an external shield, are:
- Grid No. 1 to Plate: 0.32 pF
- Grid No. 1 to Cathode, Heater, Grid No. 2, Grid No. 3, and Diode Plate: 13 pF
- Plate to Cathode, Heater, Grid No. 2, Grid No. 3, and Diode Plate: 6 pF
Electrical Characteristics and Class A1 Operation
The 17JQ6 can be characterized under Class A1 amplifier conditions. Because of the high currents drawn at low bias levels, certain characteristics must be measured using recurrent waveform methods to prevent exceeding the tube's maximum ratings.
Class A1 Operating Points
The electrical characteristics are documented under two distinct operating points:
*Measured using a recurrent waveform method to avoid exceeding maximum ratings.
**Measured with Grid No. 3 and the diode plate connected to the cathode, and Grid No. 2 connected to the plate at the socket.
Under the 140 V operating condition, the Grid-No. 1 voltage required to reduce the plate current to 1 mA is -37 V.
Integral Diode Characteristics
The integral diode, which shares its connection with grid No. 3, exhibits the following typical characteristic:
- Instantaneous Diode-Plate-to-Cathode Voltage Drop: 5 V at an instantaneous diode-plate current of 2 mA.
Vertical-Deflection Amplifier Service and Ratings
In television receivers utilizing a 525-line, 30-frame system, the 17JQ6 operates under demanding pulsed conditions. The following maximum ratings are Design-Maximum values, except where noted:
- DC Plate Voltage: 425 V
- Peak Positive-Pulse Plate Voltage (Absolute-Maximum Value): 2,000 V (The pulse duration must not exceed 15% of a vertical scanning cycle, or 2.5 ms)
- DC Grid-No. 3 and Diode-Plate Voltage: +10 V / -150 V
- DC Grid-No. 2 Voltage: 330 V
- Peak Negative-Pulse Grid-No. 1 Voltage: 150 V
- Average Cathode Current: 70 mA
- Peak Cathode Current: 250 mA
- Average Diode-Plate (and Grid-No. 3) Current: 1 mA
- Plate Dissipation: 10 W
- Grid-No. 2 Input: 2 W
- Bulb Temperature (at hottest point): 240 °C
Maximum Circuit Values
- Grid-No. 1-Circuit Resistance: 2.2 MΩ maximum for both fixed-bias (or resistor-bias) and cathode-bias operation.
Qualitative Curve Observations
The published characteristic curves for the 17JQ6 illustrate the behavior of the tube under various voltage and current conditions:
- Plate and Grid-No. 2 Current vs. Plate Voltage (at Grid-No. 2 Voltage of 140 V): At a Grid-No. 1 voltage of 0 V, the plate current rises sharply as plate voltage increases from 0 V up to approximately 50 V. At this point, it forms a distinct knee and transitions into a flatter, more gradual upward slope. The Grid-No. 2 current peaks sharply at very low plate voltages and drops to a low, stable level once the plate voltage rises above the 50 V knee.
- Plate Current vs. Plate Voltage (at Grid-No. 1 Voltage of 0 V): When plotted across a family of Grid-No. 2 voltages ranging from 60 V to 140 V, higher screen-grid voltages shift the entire plate current curve upward, raising the overall saturation current level.
- The curves are provided for Grid-No. 1 voltages ranging from 0 V down to -30 V.
Technical Summary
The 17JQ6 is a miniature, 9-pin beam power tube with an integral diode connected to grid No. 3, specifically designed for feedback-stabilized vertical-deflection-amplifier service in television receivers. It features a 16.8 V to 17.0 V heater drawing 0.45 A, a maximum plate dissipation of 10 W, and a peak positive-pulse plate voltage rating of 2,000 V. Under typical Class A1 conditions, it exhibits a transconductance of 4,200 µmhos and a plate resistance of approximately 10,500 Ω.
