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Power - TV Horizontal Output (sweep) ·BeamPower

12GT5

Beam-power horizontal-output tube for CRT television line-deflection circuits, handling approximately 6.5 kV positive plate pulses and substantial cathode current.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
B9E
Base pins
9
Nominal heater
12.6 V / 600 mA

Description

12GT5 — Beam Power Pentode

The 12GT5 and its variant, the 12GT5A, are Novar-type beam power pentodes designed primarily for use as horizontal deflection amplifiers in television receivers. These tubes are characterized by their high peak plate current capabilities, high plate dissipation ratings, and a 12.6-volt heater designed for series or parallel heater strings.

Overview and Variant Differences

The 12GT5 and 12GT5A are electrical equivalents to the 6.3-volt heater types 6GT5 and 6GT5A, respectively, differing only in their heater ratings. The 12GT5 series features a Novar T-12 construction with a 9-pin button base.

The primary distinction between the 12GT5 and the 12GT5A lies in their physical dimensions and base construction:

  • 12GT5: Utilizes a Novar Button 9-pin E9-76 base and has a maximum seated height of 3.050 inches and a maximum overall height of 3.410 inches.
  • 12GT5A: Utilizes a Novar Button 9-pin E9-88 base featuring an exhaust tip on the base. It has a shorter bulb design, with a maximum seated height of 2.500 inches and a maximum overall height of 2.880 inches.

Both variants share a maximum diameter of 1.562 inches and use the 9NZ basing configuration.

Construction, Basing, and Interelectrode Capacitances

The 12GT5 and 12GT5A are housed in a T-12 glass envelope. The 9NZ basing arrangement provides the following pin connections, viewed from the bottom of the tube:

PinConnection
Pin 1Cathode (K)
Pin 2Grid No. 1 (G1)
Pin 3Grid No. 2 (G2)
Pin 4Heater (H)
Pin 5Heater (H)
Pin 6Grid No. 1 (G1)
Pin 7Grid No. 2 (G2)
Pin 8Internal Connection (IC) — Do Not Use
Pin 9Plate (P)

The direct interelectrode capacitances of the unshielded tube are:

  • Grid No. 1 to Plate: 0.26 pF
  • Input (g1 to h + k + g2 + g3): 15 pF
  • Output (p to h + k + g2 + g3): 6.5 pF

Heater Specifications and Operating Limits

The heater is designed for operation from either an AC or DC supply. The heater characteristics and limits are as follows:

Heater ParameterValue
Heater Voltage12.6 V
Heater Current0.600 ± 0.040 A
Average Warm-up Time11 seconds

Heater-Cathode Voltage Ratings

To prevent insulation breakdown, the voltage difference between the heater and cathode must be kept within the following limits:

  • Heater Negative with Respect to Cathode: 200 V (Total DC and Peak)
  • Heater Positive with Respect to Cathode: 100 V DC (100 V maximum continuous DC, 200 V maximum Total DC and Peak)

Horizontal Deflection Amplifier Ratings

Under the Design Maximum Rating System, the maximum ratings for horizontal deflection amplifier service are:

ParameterMaximum Rating
DC Plate Supply Voltage (Boost + DC Power Supply)770 V
Peak Positive Plate Voltage6500 V
Peak Negative Plate Voltage1500 V
Grid No. 2 (Screen Grid) Voltage220 V
Negative Grid No. 1 (Control Grid) Voltage-55 V
Peak Negative Grid No. 1 Voltage330 V
Plate Dissipation17.5 W
Grid No. 2 Input3.5 W
Average Cathode Current175 mA
Peak Cathode Current550 mA
Grid No. 1 Circuit Resistance1.0 MΩ
Bulb Temperature (at hottest point)240 °C

For operation in a 525-line, 30-frame television system, the duty cycle of the horizontal voltage pulse must not exceed 15% of one horizontal scanning cycle. Additionally, when operating in stages utilizing grid leak bias, an adequate cathode bias resistor or other protective means must be employed to safeguard the tube in the event that excitation is lost.

Electrical Characteristics and Typical Operation

At a typical Class A operating point, the electrical characteristics of the 12GT5 and 12GT5A are:

  • Plate Voltage: 250 V
  • Grid No. 2 Voltage: 150 V
  • Grid No. 1 Voltage: -22.5 V
  • Plate Current: 70 mA
  • Grid No. 2 Current: 2.1 mA
  • Transconductance: 7100 µmhos
  • Plate Resistance: 15,000 Ω
  • Amplification Factor (Triode Connected): 4.4 (measured with 150 V on the plate and Grid No. 2, and -22.5 V on Grid No. 1)
  • Grid No. 1 Cutoff Voltage: -42 V (approximate value for a plate current of 1 mA)

Instantaneous Plate Knee Values

The tube is capable of delivering high peak currents at low plate voltages, as demonstrated by the following instantaneous knee values:

  • Plate Voltage (Eb): 60 V
  • Grid No. 2 Voltage (Ec2): 150 V
  • Grid No. 1 Voltage (Ec1): 0 V
  • Plate Current (Ib): 390 mA
  • Grid No. 2 Current (Ic2): 32 mA

Technical Summary

The 12GT5 and 12GT5A are high-performance Novar beam power pentodes designed for horizontal deflection amplifier service. Operating with a 12.6 V, 0.600 A heater with a controlled 11-second warm-up time, they are well-suited for series-string television designs. The 12GT5 features a standard Novar T-12 envelope, while the 12GT5A offers a more compact physical profile with an exhaust tip on the base. Both variants provide robust electrical ratings, including a peak positive plate voltage limit of 6500 V, a plate dissipation rating of 17.5 W, and the ability to deliver high peak currents at low plate voltages.

Socket description

Novar 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B9E
Base pins
9
Nominal heater voltage
12.6 V
Nominal heater current
600 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

1 physical section, each with unique specifications.

Section 1

Beam Power

X-ray radiationInterelectrode capacitances
Plate resistance
15000 Ω
Transconductance
0.0071 S
Amplification factor
4.4
Max plate voltage
770 V
Max screen voltage
220 V
Max plate dissipation
17.5 W
Max screen dissipation
3.5 W
Max cathode current
175 mA

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

1971 RCA HB3 Binder 5 of 7

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Other

  • Heater voltage

    12.6 V

  • Heater current

    600 mA

  • Maximum DC plate voltage

    770 V

    HorizontalDeflection

  • Peak positive-pulse plate voltage

    6500 V

    HorizontalDeflection

  • Maximum screen voltage

    220 V

    HorizontalDeflection

  • Average cathode current

    175 mA

    HorizontalDeflection

  • Plate dissipation

    17.5 W

  • Heater warm-up time

    11 s

    ControlledWarmup

Characteristic

  • Plate voltage

    250 V

    ClassA

  • Screen voltage

    150 V

    ClassA

  • Plate current

    70 mA

    ClassA

  • Plate resistance

    15000 ohm

    ClassA

  • Transconductance

    7100 uS

    ClassA

Capacitance

  • Grid-to-plate capacitance

    0.26 pF