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Voltage Dual Pentode ·Pentode-Pentode

4MK8

Sharp-cutoff twin pentode for television sync separation, clipping, AGC, and low-level color-demodulator circuits.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
9F6
Socket code
B9A
Base pins
9
Nominal heater
4.2 V / 450 mA

Description

Sharp-cutoff twin pentode used in television sync-separator, clipper, AGC and low-level color-demodulator circuits. Extracted from the supplied RCA Receiving Tube Manual excerpt.

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
9F6
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
No

9F6 - 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
0.0011 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
32 mA

Identical twin pentode sections compressed to one section row; values apply to each unit.

Section 2

Pentode

X-ray radiationInterelectrode capacitances
Transconductance
0.0011 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
32 mA

Second physical pentode section; identical twin 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

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • Grid No.3 to plate capacitance

    2 pF

    EachSection

  • Grid No.1 to all electrodes capacitance

    6 pF

    EachSection

  • Grid No.3 to all electrodes capacitance

    3.6 pF

    EachSection

  • Plate to all electrodes capacitance

    3 pF

    EachSection

  • Inter-section grid No.3 capacitance

    0.015 pF

    Max

Other

  • Plate voltage

    100 V

    ClassA

  • Screen-grid voltage

    67.5 V

    ClassA

  • Plate current

    2 mA

    ClassA

  • Cathode current

    8.5 mA

    BothUnitsOperating

  • Screen-grid current

    4.4 mA

    BothUnitsOperating