HK-257B
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BrandHeintz and Kaufman
ClassBeam Pentode
BaseGiant 7-pin Bayonet
Construction
Primary TypeBeam Pentode
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
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Radio Frequency Power Amplifier Class C Unmodulated | 3000V | - | - | - | 100mA |
| Radio Frequency Power Amplifier Class C Plate Modulated | 2500V | - | - | - | 100mA |
| Class A Amplifier Audio | 1000V | - | - | - | 75mA |
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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