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Voltage Dual Pentode ·Pentode-Pentode

4GS8

Sharp-cutoff twin pentode designed as combined television sync separator, sync clipper, and automatic-gain-control amplifier.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
-
Socket code
B9A
Base pins
9
Nominal heater
4.2 V / 450 mA

Description

Sharp-cutoff twin pentode used as combined sync separator, sync clipper, and AGC amplifier in television receivers.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B9A
Base pins
9
Nominal heater voltage
4.2 V
Nominal heater current
450 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
Yes

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
Transconductance
0.0012 S
Max plate voltage
300 V
Max screen voltage
150 V
Max plate dissipation
1.1 W
Max screen dissipation
0.75 W
Max cathode current
12 mA

Tung-Sol and Sylvania 4GS8 dual pentode for TV sync separator/clipper and AGC duties; separate plates and grid-3 electrodes, with shared screen and control structures; first physical pentode section. Heater 4.2 V, 450 mA series-string service, controlled warm-up approximately 11 s. Per-section maximum plate 300 V, plate dissipation 1.1 W; shared screen grid max 150 V, screen dissipation 0.75 W, DC cathode current max 12 mA. For separately tested section in manufacturer arrangement, grid-4-to-plate transconductance about 1200 µmhos (0.0012 S); this is a GRID-SPECIFIC conductance, not interchangeable with grid-3 response on second physical section. Typical plate 100 V and screen 67.5 V, other section grounded during separate measurements. Capacitive coupling between sections and 9LW/9FG basing variants noted.

Section 2

Pentode

X-ray radiationInterelectrode capacitances
Transconductance
0.00027 S
Max plate voltage
300 V
Max screen voltage
150 V
Max plate dissipation
1.1 W
Max screen dissipation
0.75 W
Max cathode current
12 mA

Second physical pentode section in 4GS8 shared-grid double-pentode used for television sync separator/clipper and AGC amplification. Unlike first section's grid-4 conductance, this section's grid-3-to-plate transconductance about 270 µmhos (0.00027 S) under Tung-Sol section-isolated test conditions (100 V plate, 67.5 V screen, opposing plate and grid 3 grounded). This is a GRID-SPECIFIC measurement. Common ratings include each section plate max 300 V and dissipation 1.1 W, shared screen voltage max 150 V and dissipation 0.75 W, DC cathode current max 12 mA. Heater 4.2 V, 450 mA for controlled-warm-up series string, about 11 s.

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

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristic

  • Grid4Transconductance

    1200 uS

    Section1

SECTION 2

Pentode

Characteristic

  • Grid3 Transconductance

    270 uS

    Section2

Data set 02

1966 Tung Sol Electronic Tubes 1 of 4

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • GRID #} TO PLATE (EACH SECTION)

    2 ΜΜF

    Capacitances | GRID #} TO PLATE (EACH SECTION) 2.0 µµf

  • GRID #

    6 ΜΜF

    Capacitances | GRID #1 TO ALL 6.0 µµf

  • GRID #} (EACH SECTION) TO ALL

    3.8 ΜΜF

    Capacitances | GRID #} (EACH SECTION) TO ALL 3.8 µµf

  • PLATE (EACH SECTION) TO ALL

    3.2 ΜΜF

    Capacitances | PLATE (EACH SECTION) TO ALL 3.2 µµf

  • GRID #

    0.015 ΜΜF

    Capacitances | GRID #3 (SECTION 2) (MAX.) 0.015 µµf

Other

  • HEATER VOLTAGE

    4.2 V

    Maximum Ratings | HEATER VOLTAGE 4.2 VOLTS

  • MAXIMUM PLATE DISSIPATION (EACH SECTION)

    1.1 W

    Maximum Ratings | MAXIMUM PLATE DISSIPATION (EACH SECTION) 1.1 WATTS

  • MAXIMUM GRID #

    0.75 W

    Maximum Ratings | MAXIMUM GRID #2 DISSIPATION 0.75 wATTs

  • MAXIMUM DC CATHODE CURRENT

    12 mA

    Maximum Ratings | MAXIMUM DC CATHODE CURRENT 12 MA.

  • MAXIMUM GR ID #f CIRCUIT RESISTANCE O

    5 Mohm

    Maximum Ratings | MAXIMUM GR ID #f CIRCUIT RESISTANCE O.5 MEGOHM

  • MAXIMUM GRID #

    5 Mohm

    Maximum Ratings | MAXIMUM GRID #3 CIRCUITRESISTANCE (EACH SECTION) O.5 MEGOHM

  • HEATER WARM— UP TIME (AP PROX.) *

    11 s

    Maximum Ratings | HEATER WARM— UP TIME (AP PROX.) * 11.0 SECONDS

  • HEATER VOLTAGE lj

    2 V

    Typical Operating Conditions | HEATER VOLTAGE lj.2 VOLTS

  • PLATE VOLTAGE (EACH SECTION)

    100 V

    Typical Operating Conditions | PLATE VOLTAGE (EACH SECTION) 100 100 VOLTS

  • GRID #

    67.5 V

    Typical Operating Conditions | GRID #2 VOLTAGE 67.5 67.5 voLTs

  • PLATE CURRENT (EACH SECTION)

    2 mA

    Typical Operating Conditions | PLATE CURRENT (EACH SECTION) 2.0 MA.

  • GRID #

    3.6 mA

    Typical Operating Conditions | GRID #2 CURRENT 6.0 3.6 MA..

  • CATHODE CURRENT

    7.7 mA

    Typical Operating Conditions | CATHODE CURRENT 6.1 7.7 MA.

  • PLATE CURRENT

    2 mA

    Typical Operating Conditions | PLATE CURRENT 2.0 MA.

  • GRID #

    270 ΜMHOS

    Typical Operating Conditions | GRID #3 TRANSCONDUCTANCE 270 µMHOS

  • GRID #

    1200 ΜMHOS

    Typical Operating Conditions | GRID #1 TRANSCO ND UCTANCE 1200 µMHOS

Data set 03

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Tube Voltage Drop for plate current of

    140 mA

    Published in approved 4GS8 target entry; Section1

  • Tube Voltage Drop for plate current of 140 mA

    12 V

    Published in approved 4GS8 target entry; Section1

  • Heater Voltage (ac/dc) 3.15 4.2

    6.3 V

    Published in approved 4GS8 target entry; Section1

  • Heater Current 0.6 0.45

    300 mA

    Published in approved 4GS8 target entry; Section1

  • Heater Warm-up Time (Average) 11

    11 seconds

    Published in approved 4GS8 target entry; Section1

  • Plate Voltage (Each Unit)

    300 V

    Published in approved 4GS8 target entry; Section1

  • Peak positive value

    50 V

    Published in approved 4GS8 target entry; Section1

  • DC negative value

    50 V

    Published in approved 4GS8 target entry; Section1

  • DC positive value

    3 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.2 (Screen-Grid) Voltage

    150 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.l (Control-Grid) Voltage, Negative bias value

    50 V

    Published in approved 4GS8 target entry; Section1

  • Cathode Current

    12 mA

    Published in approved 4GS8 target entry; Section1

  • Plate Dissipation (Each Unit)

    1.1 W

    Published in approved 4GS8 target entry; Section1

  • Grid-No.2 Input

    0.75 W

    Published in approved 4GS8 target entry; Section1

  • Plate Voltage (Each Unit) 100

    100 V

    Published in approved 4GS8 target entry; Section1

  • Plate Current

    2.2 mA

    Published in approved 4GS8 target entry; Section1

  • 100 aA —

    -4.6 V

    Published in approved 4GS8 target entry; Section1

  • 100 M —

    -2.3 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.3-Circuit Resistance (Each Unit)

    0.5 MΩ

    Published in approved 4GS8 target entry; Section1

  • Grid-No.l-Circuit Resistance

    0.5 MΩ

    Published in approved 4GS8 target entry; Section1

  • ORID-No

    3 V

    Published in approved 4GS8 target entry; Section1

  • GRID-No

    2 V

    Published in approved 4GS8 target entry; Section1

  • Heater Voltage (ac/dc) 6.3

    12.6 V

    Published in approved 4GS8 target entry; Section1

  • Heater Current 0.9

    450 mA

    Published in approved 4GS8 target entry; Section1

  • Heater Warm-up Time

    11 seconds

    Published in approved 4GS8 target entry; Section1

  • DC Plate Voltage

    300 V

    Published in approved 4GS8 target entry; Section1

  • Positive-bias value

    25 V

    Published in approved 4GS8 target entry; Section1

  • Negative-bias value

    100 V

    Published in approved 4GS8 target entry; Section1

Capacitance

  • Grid No. 3 to Plate (Each Unit)

    1.9 pF

    Published in approved 4GS8 target entry; Section1

  • Grid No.l to All Other Electrodes

    6 pF

    Published in approved 4GS8 target entry; Section1

  • Grid No.3 to All Other Electrodes (Each Unit)

    3.6 pF

    Published in approved 4GS8 target entry; Section1

  • Plate to All Other Electrodes (Each Unit)

    3 pF

    Published in approved 4GS8 target entry; Section1

  • Grid No.l to Plate

    0.1 pF

    Published in approved 4GS8 target entry; Section1

  • Internal Shield

    7 pF

    Published in approved 4GS8 target entry; Section1

  • Grid No.3 to All Other Electrodes

    8.5 pF

    Published in approved 4GS8 target entry; Section1

  • Grid No.l to Grid No.3

    0.08 pF

    Published in approved 4GS8 target entry; Section1

Characteristic

  • Grid-No-3 Voltage (Each Unit) —10

    0 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.2 Voltage 67.6

    67.5 V

    Published in approved 4GS8 target entry; Section1

  • Plate Current (Each Unit)

    2.2 mA

    Published in approved 4GS8 target entry; Section1

  • Grid-No.2 Current 6.5

    3.3 mA

    Published in approved 4GS8 target entry; Section1

  • Cathode Current 6.6

    7.8 mA

    Published in approved 4GS8 target entry; Section1

  • Plate Voltage 100

    100 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.3 Voltage 0

    0 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.2 Voltage 67.5

    67.5 V

    Published in approved 4GS8 target entry; Section1

  • Grid-No.3 Transconductance

    180 µS

    Published in approved 4GS8 target entry; Section1