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Rectifier - Half Wave ·Rectifier

258B

Air-cooled directly heated half-wave mercury-vapor rectifier for substantial high-voltage supplies. Rated for approximately 7.5 kV peak inverse voltage and 375 mA nominal output with a low forward drop.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
UX4
Base pins
4
Nominal heater
2.5 V / 7.5 A

Description

Air-cooled half-wave mercury-vapor rectifier with an oxide-coated filament, rated for 7500 V peak inverse anode voltage.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
UX4
Base pins
4
Nominal heater voltage
2.5 V
Nominal heater current
7.5 A
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

Rectifier

X-ray radiationInterelectrode capacitances
Rectifier peak inverse voltage
7500 V
Rectifier nominal output current
375 mA
Rectifier peak forward current
2.5 A
Rectifier forward voltage drop
15 V
Rectifier warm-up time
15 s

Maximum average anode current 0.64 A; later combined 249B/258B bulletin used.

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

1940 Taylor Tubes

Published operating points and test conditions from this source.

SECTION 1

Rectifier

Other

  • Peak inverse voltage

    10000 V

    CondensedMercuryTemperature=20-60C

  • Peak inverse voltage

    5000 V

    CondensedMercuryTemperature=20-70C

  • RMS AC input voltage

    3530 V

    SinglePhaseFullWaveTwoTubes

  • Maximum DC output voltage

    3180 V

    SinglePhaseFullWaveTwoTubes

  • Maximum DC output current

    750 mA

    SinglePhaseFullWaveTwoTubes

  • RMS AC input voltage

    7060 V

    SinglePhaseBridgeFourTubes

  • Maximum DC output voltage

    6360 V

    SinglePhaseBridgeFourTubes

  • Maximum DC output current

    750 mA

    SinglePhaseBridgeFourTubes

  • RMS AC input voltage

    4080 V

    ThreePhaseHalfWaveThreeTubes

  • Maximum DC output voltage

    4780 V

    ThreePhaseHalfWaveThreeTubes

  • Maximum DC output current

    1.12 A

    ThreePhaseHalfWaveThreeTubes

  • RMS AC input voltage

    4080 V

    ThreePhaseParallelDoubleYSixTubes

  • Maximum DC output voltage

    4780 V

    ThreePhaseParallelDoubleYSixTubes

  • Maximum DC output current

    2.25 A

    ThreePhaseParallelDoubleYSixTubes

  • RMS AC input voltage

    4080 V

    ThreePhaseFullWaveSixTubes

  • Maximum DC output voltage

    9560 V

    ThreePhaseFullWaveSixTubes

  • Maximum DC output current

    1.12 A

    ThreePhaseFullWaveSixTubes

Data set 02

1956 Western Electric Tubes

Published operating points and test conditions from this source.

SECTION 1

Rectifier

Other

  • Filament Voltage

    2.5 V

  • Filament Current

    7.5 A

  • Peak Inverse Anode Voltage

    7500 V

  • Maximum Peak Anode Current

    2.5 A

    InPhase

  • Maximum Average Anode Current

    640 mA

    InPhase

  • Maximum Averaging Time

    5 s

Characteristic

  • Condensed Mercury Temperature Range

    20-70 °C

Data set 03

2026 Western Electric 200s

Published operating points and test conditions from this source.

SECTION 1

Rectifier

Other

  • MaximumAverageAnodeCurrent

    640 mA

  • Maximum Peak Inverse Anode Voltage

    7500 V

    AmbientTemperature=0to50C

  • RequiredHeatingTime

    15 s

  • LoadCurrent

    640 mA

    SinglePhaseHalfWave;LoadPotential=2300V

Characteristic

  • AnodeCathodeVoltageDrop

    15 V

    Approximate