Tube-number record
28D7
0 archive entries
28D7 is a tube type in the TubeDatabase archive (class: Rugged double beam power tube). Recorded specifications: brand Sylvania, construction Beam tetrode / beam power, socket Loctal, maximum plate voltage 100 V, and maximum plate dissipation 3 W. The archive does not yet hold a photographed example of this type.
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
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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