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Power - Pentode (NOT beam) ·Diode-Diode-Pentode

CBL31

High-sensitivity output pentode combined with two diode sections for mains-operated receiver equipment. Manufacturer data include audio output, distortion, load, and limiting ratings for the power section.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
3
Base
-
Socket code
IO
Base pins
-
Nominal heater
44 V / 200 mA

Description

High-sensitivity output pentode for AC mains-operated equipment combined with two diode sections, with published audio output, distortion, load and limiting ratings.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
IO
Base pins
-
Nominal heater voltage
44 V
Nominal heater current
200 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

3 physical sections, each with unique specifications.

Section 1

Diode

X-ray radiationInterelectrode capacitances
Max plate voltage
200 V
Max cathode current
0.8 mA

Representative of the two diode sections.

Section 2

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
33500 Ω
Transconductance
0.008 S
Max plate voltage
250 V
Max screen voltage
250 V
Max plate dissipation
9 W
Max screen dissipation
2 W
Max cathode current
70 mA

Output pentode section.

Section 3

Diode

X-ray radiationInterelectrode capacitances
Max plate voltage
200 V
Max cathode current
0.8 mA

Second diode 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

1951 Mullard Valve and Service Manual

Published operating points and test conditions from this source.

SECTION 2

Pentode

Other

  • Anode Voltage

    200 V

    ClassA

  • Screen Voltage

    200 V

    ClassA

  • Control Grid Voltage

    -8.5 V

    ClassA

  • Anode Current

    45 mA

    ClassA

  • Screen Current

    6 mA

    ClassA

  • Optimum Load

    4500 ohm

    ClassA

  • Power Output

    4 W

    ClassA

Data set 02

1963 Mullard

Published operating points and test conditions from this source.

SECTION 1

Diode

Other

  • Diode anode voltage maximum

    200 V

  • Diode anode current maximum

    0.8 mA

  • Diode grid-current test voltage maximum

    -1.3 V

    At Id=+0.3 uA

SECTION 2

Pentode

Other

  • Anode voltage

    200 V

  • Screen voltage

    200 V

  • Control-grid voltage

    -8.5 V

  • Anode current

    45 mA

  • Screen current

    6 mA

  • Load resistance

    4500 ohm

  • Output power

    4 W

  • Total distortion

    10 %

  • Cathode resistor

    167 ohm

  • Anode supply voltage maximum

    550 V

  • Plate voltage maximum

    250 V

  • Plate dissipation maximum

    9 W

  • Cathode current maximum

    70 mA

  • Screen supply voltage maximum

    550 V

  • Screen voltage maximum

    250 V

  • Screen dissipation maximum

    2 W

  • Heater-cathode voltage maximum

    125 V

Characteristic

  • Transconductance

    8000 uS

  • Plate resistance

    35000 ohm

SECTION 3

Diode

Other

  • Diode anode voltage maximum

    200 V

  • Diode anode current maximum

    0.8 mA

  • Diode grid-current test voltage maximum

    -1.3 V

    At Id=+0.3 uA