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Power - Pentode (NOT beam) ·Pentode-Pentode

17X10

Dual-pentode television sound tube combining gated-beam FM limiter/discriminator service with a separate audio power-output pentode.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: -
Socket code: B12C
Base pins: -
Nominal heater: 16.8 V / 450 mA

Description

17X10 — Double Dissimilar Pentode

The 17X10 is a multi-section Compactron vacuum tube containing two highly dissimilar pentode sections in a single envelope. It is designed for use in television and radio receivers, where Section 1 serves as an FM limiter/discriminator (gated beam discriminator) and Section 2 serves as an audio power amplifier. The tube features a controlled heater warm-up time for series-string applications.

Mechanical Design and Basing Connection

The 17X10 is housed in a T-9 glass bulb (Compactron) with a button 12-pin base (E12-70). The physical outline is designated as 9-58 or 9-59. The tube can be operated in any mounting position.

The physical dimensions are:

Maximum Diameter: 1.188 inches
Maximum Seated Height: 2.250 inches
Maximum Overall Height: 2.625 inches

Both sections utilize coated unipotential cathodes. The tube uses the 12BT basing configuration, with the following pin assignments:

Pin 1: Grid No. 1 (Section 1) [1G1]
Pin 2: Grid No. 3 (Section 1) [1G3]
Pin 3: Grid No. 2 (Section 2) [2G2]
Pin 4: Cathode (Section 2) [2K]
Pin 5: Grid No. 1 (Section 2) [2G1]
Pin 6: Grid No. 1 (Section 1) [1G1]
Pin 7: Grid No. 2 (Section 1) [1G2]
Pin 8: Cathode, Shield (Section 1) [1K, 1S]
Pin 9: Plate (Section 2) [2P]
Pin 10: No Connection [NC]
Pin 11: Grid No. 1 (Section 2) [2G1]
Pin 12: Heater [H]

Heater Characteristics and Ratings

The heater is designed for series-string operation and features a controlled warm-up time to minimize voltage surges in series-connected heater chains.

Heater Voltage: 16.8 Volts
Heater Current (Average): 450 mA
Heater Current Limits (Design Maximum): 420 to 480 mA
Heater Warm-up Time: 11 Seconds

Heater-Cathode Voltage Limits

The maximum ratings for the voltage between the heater and cathode are:

Heater Negative with Respect to Cathode (Total DC and Peak): 200 Volts
Heater Positive with Respect to Cathode (DC): 100 Volts
Heater Positive with Respect to Cathode (Total DC and Peak): 200 Volts

Direct Interelectrode Capacitances

The direct interelectrode capacitances are measured without an external shield:

Section No. 1

Grid No. 1 to ( $h + 1k + 1g_2 + 1g_3 + IS$ ): 4.4 pF
Grid No. 3 to ( $h + 1k + 1g_1 + 1g_2 + 1p + IS$ ): 3.2 pF
Grid No. 1 to Grid No. 3: 0.005 pF

Section No. 2

Grid to Plate: 0.24 pF
Input ( $g$ to $h + 2k + 2g_2 + g_3 + 1k + IS$ ): 12.0 pF
Output ( $p$ to $h + 2k + 2g_2 + g_3 + 1k + IS$ ): 9.0 pF

Design Maximum Ratings

The maximum ratings are defined under the Design Maximum Rating System:

Section No. 1 (Limiter/Discriminator)

Plate Supply Voltage: 330 Volts
Accelerator Voltage ( $G_2$ ): 110 Volts
Peak Positive $G_1$ Voltage: 60 Volts
DC Cathode Current: 13 mA

Section No. 2 (Power Pentode)

Plate Voltage: 165 Volts
Screen Voltage: 150 Volts
Plate Dissipation: 6.5 Watts
Screen Dissipation: 1.8 Watts
DC Cathode Current: 65 mA
Grid No. 1 Circuit Resistance (Fixed Bias): 0.25 Megohms
Grid No. 1 Circuit Resistance (Cathode Bias): 0.5 Megohms

Typical Operation and Electrical Characteristics

Section No. 1: Limiter/Discriminator Service

Section 1 is designed to operate as a gated beam discriminator. Typical operating parameters are specified for three distinct circuit configurations:

Parameter	Case A (10.7 MHz)	Case B (10.7 MHz)	Case C (4.5 MHz)
Input Signal Center Frequency	10.7 MHz	10.7 MHz	4.5 MHz
Frequency Deviation	±75 kHz	±75 kHz	±25 kHz
Plate Supply Voltage	85 V	285 V	270 V
Plate Voltage	62 V	122 V	121 V
Accelerator Voltage	55 V	100 V	100 V
Cathode Bias Resistor (Variable)	200–400 Ω	200–400 Ω	200–400 Ω
Plate Load Resistor	0.085 MΩ	0.330 MΩ	0.330 MΩ
Plate Linearity Resistor	470 Ω	1500 Ω	1000 Ω
Integrating Capacitor	0.002 µF	0.001 µF	0.001 µF
Coupling Capacitor	0.25 µF	0.01 µF	0.25 µF
Minimum Signal Voltage for Limiting (rms)	1.25 V	1.25 V	1.25 V
DC Plate Current	0.25 mA	0.49 mA	0.44 mA
Accelerator Current	4.1 mA	9.8 mA	10 mA
Input Signal Level for AM Rejection Adj.	1.25 V	2.0 V	2.0 V
AM Rejection at $E_{sig}$ = 2.0 V rms	31 dB	20 dB	25 dB
AM Rejection at $E_{sig}$ = 3.0 V rms	30 dB	29 dB	30 dB
Total Harmonic Distortion	2.0%	1.6%	1.8%
Peak Audio Output Voltage	6.0 V	16.6 V	16.8 V

Circuit Application Guidelines

AM Rejection Adjustment: The variable cathode resistor must be adjusted to achieve maximum AM rejection in the output of the limiter-discriminator stage at the specified signal level (measured with 30% AM and 30% FM).
Limiting Performance: Above the specified input signal level, limiting is maintained within ±3 dB. Proper phasing requires adequate shielding between the components of the limiter grid and the quadrature grid.
Quadrature Grid Circuit: The Q of the quadrature grid circuit must be high enough to develop a minimum of 4 V (rms) signal with 2 V (rms) of the center-frequency signal applied to the limiter grid. The coil should be shunted by a minimum of 10 pF, which includes the tube input, stray, distributed, and physical capacitances.

Section No. 2: Audio Power Amplifier

Section 2 is operated as a class-A power amplifier. Typical operating parameters are:

Plate Voltage: 145 Volts
Screen Voltage: 110 Volts
Grid No. 1 Voltage: -6.0 Volts
Peak AF Grid Voltage: 6.0 Volts
Plate Resistance (Approx.): 30,000 Ohms
Transconductance: 8600 µmhos
Zero Signal Plate Current: 36 mA
Maximum Signal Plate Current: 40 mA
Zero Signal Screen Current: 3.0 mA
Maximum Signal Screen Current: 9.0 mA
Load Resistance: 3000 Ohms
Total Harmonic Distortion (Approx.): 10%
Maximum Signal Power Output: 2.1 Watts

Technical Summary

The 17X10 is a Compactron double dissimilar pentode designed for series-string television and radio receivers. It combines a gated beam discriminator (Section 1) and an audio power amplifier (Section 2) in a single T-9 envelope. The tube features a 16.8 V, 450 mA heater with an 11-second controlled warm-up time. Section 1 provides effective FM demodulation at 4.5 MHz or 10.7 MHz with up to 31 dB of AM rejection and low distortion. Section 2 provides up to 2.1 Watts of audio output power with a transconductance of 8600 µmhos, offering a compact, integrated solution for receiver design.

Socket description

Duodecar 12-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: B12C
Base pins: -
Nominal heater voltage: 16.8 V
Nominal heater current: 450 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Max plate voltage: 330 V
Max screen voltage: 110 V
Max cathode current: 13 mA

Gated-beam limiter/discriminator pentode section.

Section 2

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 30000 Ω
Transconductance: 0.0086 S
Max plate voltage: 165 V
Max screen voltage: 150 V
Max plate dissipation: 6.45 W
Max screen dissipation: 1.8 W
Max cathode current: 65 mA

Audio power pentode section.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1964 RMA EIA

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

Heater Voltage
16.8 V
SeriesHeater
Heater Current
450 mA
SeriesHeater
Heater Warm-up Time
11 s
Grid1-to-Other Electrodes Capacitance
10.1 pF
Section1
Grid3-to-Other Electrodes Capacitance
30.2 pF
Section1
Grid1-Grid3 Capacitance
0.005 pF
Section1

Other

Maximum Plate Supply Voltage
330 V
Section1
Maximum Accelerator Voltage
110 V
Section1
Maximum Peak Positive Grid1 Voltage
60 V
Section1
Maximum DC Cathode Current
13 mA
Section1
Center Frequency
10.7 MHz
LimiterDiscriminator
Frequency Deviation
75 kHz
LimiterDiscriminator; Representative
Peak Audio Output Voltage
16.8 V
LimiterDiscriminator; Representative

SECTION 2

Pentode

Other

Maximum Plate Voltage
165 V
Section2
Maximum Screen Voltage
150 V
Section2
Maximum Plate Dissipation
6.45 W
Section2
Maximum Screen Dissipation
1.8 W
Section2
Maximum DC Cathode Current
65 mA
Section2
Plate Voltage
165 V
PowerAmplifier
Screen Voltage
110 V
PowerAmplifier
Grid Voltage
-6 V
PowerAmplifier
Load Resistance
3000 ohm
PowerAmplifier
Maximum Signal Power Output
2.1 W
PowerAmplifier
Total Harmonic Distortion
16 percent
PowerAmplifier

Characteristics

Grid-Plate Capacitance
0.24 pF
Section2
Input Capacitance
12 pF
Section2
Output Capacitance
9 pF
Section2
Plate Resistance
30000 ohm
Section2
Transconductance
8600 uS
Section2