Tube-number record
SB21
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BrandElectrons, Inc. of Delaware
ClassFull-wave Rectifier
BaseOctal
Construction
Primary TypeRectifier
Rectifier TypeArgon Gas Filled
EnvelopeGlass
Base MaterialUX Radio Base
Sections2
Filament / Heater
MaterialUnknown
Warm-up Time15s
Absolute Maximum Ratings
Plate Voltage500 V
Cathode Current1000 mA
Audio Performance
Key Features
- Graphite Anodes
- Argon Gas Filling
- Full-wave Rectifier
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Max ratings at low current | 175 V | — | — | — | 400 mA |
| Max ratings at standard current | 145 V | — | — | — | 1000 mA |
| Max ratings at high current | 55 V | — | — | — | 1250 mA |
Application Notes
It is preferable, but not essential, to light the filament before applying d-c. load. If omitted, each cold start at 1 ampere, 145 volts per plate consumes approximately one hour of tube life.
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