Data: MediumMedium quality — at least 60% of universal parameters and pins are present, but some key data is missing. Verify specific values against datasheets before critical use.
Later general-purpose DHT amplifier/detector triode on the same UX4 base and 5V/0.25A filament, but hard vacuum (not vapor type) with lower mu (≈8) and rated for Class A amplifier service up to 135V
UX-200
Original argon-filled predecessor (type 200); the 00A replaced it using cesium vapor and a reduced-current thoriated filament
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Plate Voltage (max)45V
Typical Operating
Anode Voltage (typical)Plate Voltage (detector)45V
Grid 1 Bias VoltageGrid Voltage (detector)0V
Anode CurrentPlate Current1.5mA
Notes
Vapor/soft detector — the envelope is not a hard vacuum. A small amount of cesium vapor (reported; earlier type 200 used argon) enhances grid-leak detection sensitivity but makes the tube unsuitable for amplifier service. Do not substitute for a hard-vacuum triode such as the 01A without understanding this difference.
Intended for grid-leak detection only. Typical operation: plate 45 V (maximum), grid return to (−) filament, grid leak 2 or 3 MΩ, grid condenser 0.00025 µF (250 pF).
No explicit Pa_max on the RCA datasheet — maximum plate voltage is 45 V and at 1.5 mA detector current the dissipation is ≈0.07 W, well below any practical limit.
Filament is thoriated tungsten, directly heated, 5.0 V DC at 0.25 A. Historically one of the earliest widely used American detector triodes; descended from the original UV-200 of 1920 and introduced as UX-200-A when RCA adopted the UX4 bayonet base in 1925.
Pin Layout — UX4
1Filament +
2Plate
3Grid
4Filament -
Socket-Compatible Tubes ⚠ Not electrically compatible