| Type | Substitutes | Base Diagram |
|---|---|---|
| 31 |  | |
| Web References | 31 (RCA) @ Franks Electron Tubes 31 (RCA (HB3)) @ Franks Electron Tubes 31 (Sylvania) @ Franks Electron Tubes 31 (Tung-Sol) @ Franks Electron Tubes 31 @ RadioMuseum.org | |
| Bulb | ST-12 |
| Base | Small 4 Pin |
| Basing | 4D |
| Filament Voltage | 2.0 | Volts |
| Filament Current | 0.130 | Amps |
| Plate Voltage | 135 | 180 | Volts |
| Grid Voltage | -22.5 | -30.0 | Volts |
| Plate Current | 8.0 | 12.3 | Ma |
| Plate Resistance | 4100 | 3600 | Ohms |
| Amplification Factor | 3.8 | 3.8 | x |
| Transconductance | 925 | 1050 | �mhos |
| Load Resistance | 7000 | 5700 | Ohms |
| Undistorted Power Output | 0.185 | 0.375 | Watt |