Tube-number record
28D7
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BrandSylvania
ClassRugged double beam power tube
BaseLoctal
Filament28 V @ 400 mA
Construction
Primary TypeBeam tetrode / beam power
EnvelopeGlass
Sections2
Filament / Heater
Heater NotesAbs. Max. 30 Volts, Design Center 28 Volts
Absolute Maximum Ratings
Plate Voltage100 V
Plate Dissipation3 W
Grid 2 Voltage67.5 V
H-C Voltage100 V
Audio Performance
Typical THD10%
Power Output0.1 W
Key Features
- Rugged double beam power tube
- Lockin base
- Designed for airplane or mobile service
- High shock and vibration resistance
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Class A1 Amplifier (Each Section, Fixed Bias) | 28 V | 3400 | 4200 | — | 12.5 mA |
| Push-Pull Resistance Coupled Class A1 (Both Sections, Fixed Bias) | 28 V | — | — | — | 25 mA |
| Parallel Resistance Coupled Class A1 (Both Sections, Fixed Bias) | 28 V | — | — |
Application Notes
The two sections may be operated separately, connected in parallel, or in a push-pull circuit. Designed for low voltage (28V) operation in mobile equipment.
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