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Power - Triode ·Triode-Triode

33A138A

Twin power triode containing two identical sections for high-frequency RF amplification. The paired systems provide compact push-pull transmitter operation, with published output around 14 W and useful service extending to approximately 300 MHz.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
-
Socket code
MEDIUM7
Base pins
7
Nominal heater
6.3 V / 800 mA

Description

Twin triode; both sections identical; identical-section compression applied.

Socket description

Medium 7-contact transmitting-tube base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
MEDIUM7
Base pins
7
Nominal heater voltage
6.3 V
Nominal heater current
800 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

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
4700 Ω
Amplification factor
14
Max plate voltage
300 V
Max plate dissipation
5 W
Max cathode current
50 mA

Representative section for repeated identical physical sections.

Section 2

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
4700 Ω
Amplification factor
14
Max plate voltage
300 V
Max plate dissipation
5 W
Max cathode current
50 mA

Identical second physical section; duplicated from representative section per physical-section-row policy.

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

1946 Standard Telephone and Cables

Published operating points and test conditions from this source.

SECTION 1

Triode

Capacitance

  • Grid-anode capacitance

    2.7 pF

  • Grid-cathode capacitance

    6 pF

  • Anode-cathode capacitance

    0.3 pF

Other

  • Maximum frequency for ratings

    100 MHz

  • Maximum frequency of operation

    300 MHz

Data set 02

1947 Standard Valves

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Maximum frequency at full ratings

    100 MHz

  • Maximum operating frequency

    300 MHz

  • RF power output

    14 W