Later WE type with higher current rating — different maximum ratings, not a direct drop-in replacement
4274A
STC (Standard Telephones & Cables) equivalent designation for the 274A — same UX4 base and 5V/2A filament but may have slightly different ratings per STC specs
Same UX4 base but lower current rating (125 mA) and lower max voltage — predecessor generation rectifier
CV1451
British CV designation listed as normally replaceable but slightly different per radiomuseum
Electrical Specifications
Absolute Maximum
Anode Voltage (max)AC Voltage per Plate (max RMS, choke-input)550V
Rectifier
Peak Inverse VoltagePeak Inverse Voltage1,500V
Voltage Drop (typical)Tube Voltage Drop (derived from Fig. 3)80V
Max C-input Filter CapacitorMax C-input Filter Capacitor4µF
Notes
Directly heated (filament cathode) — observe heater warm-up time before applying B+ to protect the tube and filter capacitors.
Choke-input filter preferred over condenser-input filter for better regulation and longer tube life.
With choke-input filter: max 550 V RMS per plate at 200 mA, or 660 V RMS at 160 mA (maximum operating condition).
With condenser-input filter: max 450 V RMS per plate at 150 mA (maximum with 4 µF capacitor).
Input condenser should preferably not exceed 4 µF with condenser-input filter.
A less severe operating condition should be selected wherever possible — tube life at maximum conditions may be shorter.
Double the listed rectified current may be obtained by connecting the two plates together and using one tube in each side of the circuit.
Socket: Western Electric 143B or equivalent standard four-contact type.
Mounting: vertical or horizontal. If horizontal, filament planes should be vertical.
A development of Bell Telephone Laboratories, American Telephone and Telegraph Company, and Western Electric Company.
Vdrop ≈ 80V derived from WE 274A datasheet Fig. 3 (single-plate I/V curve) at 200 mA per-plate instantaneous current — corresponds to full rated 200 mA DC output with choke-input filter, where each plate conducts the full load current during its half cycle. WE does not publish Vdrop as a discrete value; it must be read off the curve. The 274A's relatively high drop (~80V vs ~58V for 5Z3/5U4) is intentional — WE designed it as a 'soft' rectifier for gradual B+ ramp-up in their amplifiers.
Pin Layout — UX4
1Anode 1 (Plate 1)
2Filament
3Anode 2 (Plate 2)
4Filament
Socket-Compatible Tubes ⚠ Not electrically compatible