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Tube Database (7,341 tube types · 1,270 archive entries)

Pre (2,630 tube types), Other (2,603 tube types), Power (1,292 tube types), Rectifier (816 tube types)
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Tube-number record

HK-257B

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BrandHeintz and Kaufman
ClassBeam Pentode
Base7-pin (non-miniature)

Construction

Primary TypeBeam tetrode / beam power
EnvelopeNonex Glass
Base MaterialGiant 7-pin Bayonet
SectionsSingle

Filament / Heater

MaterialThoriated Tungsten

Absolute Maximum Ratings

Plate Voltage4000 V
Plate Dissipation75 W
Grid 2 Voltage750 V
Grid 1 Voltage-500 V
Cathode Current150 mA

Audio Performance

Key Features
  • Radiation cooled
  • Tantalum plate and grid elements
  • No neutralization required
  • Very high frequency performance
  • Instant band switching capability

Typical Operation

ModePlate VGm (µmhos)Rp (Ω)µPlate mA
Radio Frequency Power Amplifier Class C Unmodulated3000 V———100 mA
Radio Frequency Power Amplifier Class C Plate Modulated2500 V———100 mA
Class A Amplifier Audio1000 V———75 mA

Application Notes

Always provide sufficient fixed bias or cathode bias to limit the plate current. Plate current depends on screen voltage. Apply screen voltage or excitation after or at the same time as plate voltage. Output and input circuits must be completely separated to prevent self-oscillation.

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