ZA1

Marconi acorn high-frequency pentode providing useful RF gain above 50 MHz and explicitly suitable as a suppressor-grid frequency changer. Its compact construction supports early VHF receiver and measurement applications.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: -
Base pins: 7
Nominal heater: 4 V / 250 mA

Description

Marconi acorn pentode designed to maintain useful high-frequency gain above 50 Mc/s; also suitable as a suppressor-grid frequency changer or compact valve voltmeter.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: -
Base pins: 7
Nominal heater voltage: 4 V
Nominal heater current: 250 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

Pentode

X-ray radiationInterelectrode capacitances

Max plate voltage: 250 V
Max screen voltage: 100 V

Acorn pentode. Approximate-data box gives 4.0 V / 0.25 A heater and 250 V anode / 100 V screen nominal ratings; published capacitances and HF operating point retained as parameters.

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

1955 Marconi

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

Grid-Anode Capacitance
0.007 pF
Anode-AllOtherElectrodes Capacitance
3 pF
Grid-AllOtherElectrodes Capacitance
3 pF

Other

Typical Anode Voltage
250 V
HFAmplifier
Typical Screen Voltage
100 V
HFAmplifier
Typical Grid Voltage
-3 V
HFAmplifier
Typical Bias Resistance
1500 ohm
HFAmplifier

Characteristic

HF Gain Frequency Threshold
50 MHz
Datasheet states useful HF gain above 50 Mc/s
Frequency Changer Service
1 boolean
SuppressorGridInjection
Valve Voltmeter Service
1 boolean