17KV6A — Beam Power Tube

The 17KV6A is a Novar-type beam power tube (also classified as a beam power pentode) designed primarily for high-voltage pulse- or shunt-regulator applications in color television receivers. It features a T-12 glass envelope with a 9-pin button base. The tube is electrically identical to the 6KV6A and 22KV6A except for its heater ratings, which are optimized for series-string heater chains requiring a nominal 16.8 V, 0.6 A supply with a controlled warm-up time.

Construction, Mechanical Data, and Basing

The 17KV6A utilizes a Novar T-12 construction with an exhaust tip located on the bottom of the envelope. It requires a standard 9-contact socket to accommodate its button 9-pin base (E9-88). The physical dimensions of the tube are:

• Maximum Diameter: 1.562 inches
• Maximum Seated Height: 3.000 inches
• Maximum Overall Height: 3.380 inches
• Outline Designation: 12-96 or 31D

The tube conforms to the 9QU basing diagram, which assigns the internal electrodes to the following pin connections:

Heater and Cathode Ratings

The heater of the 17KV6A is designed for series-string or parallel operation, with a controlled warm-up characteristic to minimize voltage surges in series-connected heater strings.

• Heater Voltage (AC or DC): 16.8 V
• Heater Current: 0.6 A (600 ± 40 mA)
• Average Heater Warm-up Time: 11 seconds

Heater-Cathode Voltage Limits

To prevent insulation breakdown between the heater and the cathode, the following maximum voltage limits must be observed:

• Heater Negative with Respect to Cathode (Total DC and Peak): 500 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 Heater-Cathode Voltage: 100 V max.

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the 17KV6A, measured without an external shield, are approximately:

• Grid No. 1 to Plate: 0.6 pF
• Input ($G_1$ to $K, G_3, G_2, H$): 22 pF
• Output ($P$ to $K, G_3, G_2, H$): 9.0 pF

Electrical Characteristics and Typical Operation

The 17KV6A can be operated under different conditions. The published typical characteristics are divided into two distinct operating points:

Condition A (High-Current Low-Voltage State)

To prevent exceeding the maximum dissipation ratings during testing or operation at zero bias, measurements under this condition are performed using a recurrent waveform:

• DC Plate Voltage: 100 V
• DC Grid No. 3 Voltage: 0 V
• DC Grid No. 2 Voltage: 140 V
• DC Grid No. 1 Voltage: 0 V
• DC Plate Current: 440 mA
• DC Grid No. 2 Current: 30 mA

Condition B (Linear Amplifier State)

Under standard static conditions, the typical characteristics are:

• DC Plate Voltage: 140 V
• DC Grid No. 3 Voltage: 0 V
• DC Grid No. 2 Voltage: 140 V
• DC Grid No. 1 Voltage: -24.5 V
• Triode Amplification Factor: 4 (measured with Grid No. 3 connected to cathode, and Grid No. 2 connected to plate at the socket)
• Plate Resistance (Approx.): 6,000 to 10,000 $\Omega$
• Transconductance: 6,000 to 10,000 $\mu$mhos
• DC Plate Current: 40 mA
• DC Grid No. 2 Current: 2.4 mA
• Grid No. 1 Cutoff Voltage (for $I_b = 1$ mA): -42 V

The plate resistance and transconductance values exhibit ranges in the manufacturer specifications, with plate resistance documented at approximately 6,000 to 10,000 $\Omega$ and transconductance at 6,000 to 10,000 $\mu$mhos depending on the specific reference.

High-Voltage-Pulse Shunt Regulator Service

The primary application of the 17KV6A is as a shunt regulator in color television receivers operating in a standard 525-line, 30-frame system. Under the Design-Maximum Rating System, the absolute maximum ratings for this service are:

• DC Plate Supply Voltage ($I_b = 0$ mA): 900 V max.
• Peak Positive-Pulse Plate Voltage: 6,500 V max.
• Peak Negative-Pulse Plate Voltage: 1,500 V max.
• Peak Positive-Pulse Grid No. 2 Voltage: 600 V max.
• DC Grid No. 3 Voltage: 75 V max.
• DC Grid No. 2 Voltage: 220 V max.
• DC Grid No. 1 Voltage (Negative-bias value): 250 V max.
• Peak Negative-Pulse Grid No. 1 Voltage: 330 V max.
• Peak Cathode Current: 950 mA max.
• Average Cathode Current: 275 mA max. (measured with a DC meter)
• Grid No. 2 Input: 2.0 W max.
• Plate Dissipation: 28 W max.
• Envelope Temperature (at hottest point): 240 °C max.

Operating Notes and Safety Precautions

• Pulse Duration Limits: The peak positive-pulse plate voltage rating of 6,500 V is only applicable when the pulse duration does not exceed 15% of one horizontal scanning cycle (which corresponds to 10 $\mu$s in a 525-line, 30-frame system).
• Short-Term Plate Dissipation: Plate dissipation limits are rated at 28 W maximum, though some specifications permit short-term excursions up to 32 W, while others restrict short-term operation (up to 10 seconds) to 24 W, provided the maximum envelope temperature is not exceeded.
• Grid Bias Protection: Adequate circuit precautions must be taken to protect the tube from excessive current and damage in the event of a loss of Grid No. 1 bias.
• Grid No. 1 Circuit Resistance: For resistor-bias operation, the maximum allowable Grid No. 1 circuit resistance is 1.0 M$\Omega$.

Related Designations

The 17KV6A is part of a family of identical beam power tubes designed for different heater configurations. The 6KV6A is the 6.3 V heater equivalent, while the 22KV6A is the 22.4 V (or similar) heater equivalent. These tubes share identical mechanical dimensions, basing configurations, and electrical ratings, differing only in their heater voltage and current requirements.

Technical Summary

The 17KV6A is a high-performance Novar beam power tube designed for demanding high-voltage shunt regulator and pulse applications in color television receivers. Featuring a robust 28 W plate dissipation rating, a peak positive-pulse plate voltage capability of 6,500 V, and a high peak cathode current limit of 950 mA, it is well-suited for high-stress television circuitry. Its 16.8 V, 0.6 A heater with an 11-second warm-up time makes it ideal for series-string heater designs.