Smaller half-wave mercury-vapor rectifier (250 mA avg, 5000 V PIV); same Jumbo 4-pin bayonet base family
Electrical Specifications
Rectifier
Peak Inverse VoltagePeak Inverse Anode Voltage (max, 20-60°C)10,000V
Voltage Drop (typical)Peak Tube Voltage Drop (approx)10V
DC Output Current (max)Average Anode Current (max)1,250mA
Peak Anode Current (surge)Peak Anode Current (max)5,000mA
Heater
Heater VoltageFilament Voltage5V
Heater CurrentFilament Current7.5A
Notes
Mercury-vapor tube — must be operated within a condensed-mercury temperature range of 20°C to 60°C for full 10 kV PIV rating. At 20°C to 70°C range, PIV is derated to 5000 V.
Operation at 40°C +/- 5°C is recommended for optimal performance.
Filament must be applied for at least 30 seconds before applying anode voltage to allow mercury vapor pressure to stabilize.
Filament voltage range: 4.75 to 5.25 V. Average filament current is 7.5 A, maximum 8 A.
Peak tube voltage drop is approximately 10 V — very low and essentially constant across the operating current range, which is the key advantage of mercury-vapor rectifiers.
Uses Medium-Metal-Shell Jumbo 4-Pin Bayonet Base (JETEC No.A4-29) with medium top cap (JETEC No.C1-5). Not interchangeable with UX4-based tubes.
T-18 bulb envelope. Total weight approximately 7 oz.
Shields and RF filter circuits should be provided if subjected to extraneous high-frequency fields, as these can cause breakdown effects in mercury vapor.
Fault current for 0.1 second duration: 50 mA max (at 20-70°C range). This limits the tube's ability to survive short-circuit conditions.
The 872 (without 'A' suffix) is an earlier version with different ratings — not a direct equivalent.
In half-wave single-phase service (Fig. 1 in datasheet): max transformer secondary 7000 V RMS (at 20-40°C) or 5500 V RMS (at 20-60°C), approx DC output 3200/1600 V at 1.25 A.