Tube-number record
QB 3/500
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QB 3/500 is a tube type in the TubeDatabase archive (class: Transmitting Screen-Grid Tube). Recorded specifications: brand Philips, construction Tetrode, maximum plate voltage 3000 V, and maximum plate dissipation 350 W. The archive does not yet hold a photographed example of this type.
BrandPhilips
ClassTransmitting Screen-Grid Tube
Construction
Primary TypeTetrode
EnvelopeGlass
Sections1
Filament / Heater
MaterialTungsten
Absolute Maximum Ratings
Plate Voltage3000 V
Plate Dissipation350 W
Grid 2 Voltage800 V
Audio Performance
Key Features
- No neutralizing required
- Short wave HF amplifier
- Low excitation power
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Telegraphy (HF Amplifier) | 3000 V | 2200 | — | 7.5 | 135 mA |
| Telegraphy (HF Amplifier) | 3000 V | — | — | 7.5 | — |
| Telegraphy (HF Amplifier) | 3000 V | — | — | 7.5 | — |
Application Notes
Specifically designed for HF amplifier use, especially on short waves. The screen grid allows operation without neutralization. Compatible with QB 2/75 or TC 1/75 as driver stages.
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