Tube-number record
285A
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BrandWestern Electric
ClassPentode
BaseSpecial / none
Filament2 V @ 1.6 mA
Construction
Primary TypePentode
EnvelopeGlass
Base MaterialMedium, five-pin base with bayonet pin
SectionsSingle
Filament / Heater
Heater NotesDesigned to operate on a voltage basis; AC or DC.
Absolute Maximum Ratings
Plate Voltage250 V
Grid 2 Voltage200 V
Cathode Current12.5 mA
H-C Voltage90 V
Audio Performance
Power Output1.85 W
Key Features
- Low-power suppressor-grid pentode
- Indirectly heated cathode
- Suppressor-grid permanently connected to cathode
- Small metal cap control-grid terminal
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Recommended 1 | 135 V | 860 | 140000 | 120 | 7.5 mA |
| Recommended 2 | 180 V | 880 | 153000 | 135 | 8.8 mA |
| Maximum Operating Condition | 250 V | 1020 | 137000 | 140 | 12.4 mA |
Application Notes
Audio-frequency amplifier where power outputs of approximately one watt or less are required.
Datasheets
Datasheet: 285A.pdf
Download PDFLoading datasheet...
Datasheets courtesy of Frank Philipse via Frank's Electron Tube Data Sheets.
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