5U4G is glass- shell eight- feet directly heated full-wave rectifier tube5U4G is very similar with 274B and 5Z3P, which can be replaced by each other.

Filament Voltage:
Uf...........................................................5 V
If...........................................................3 A

Maximum Ratings:
Peak Anode Reverse Voltage...................................1550 V
Peak Anode Current...........................................800 mA
Maximum Ratings:
Anode Peak Inverse Voltage...................................1500 V

Peak Anode Current...........................................750 mA

Recommended Operating Conditions:
For Capacitor Input:
Supply Voltage per Anode....................................300 - 450 V
Transformer Impedance per Arm...............................35 - 85 Ω
Capacitor Input Filter.......................................40 - 40 μF
Output DC Current...........................................245 - 220 mA
Output DC Voltage...........................................290 - 470 V

For Inductive Input:
Supply Voltage per Anode....................................550 V
Input Inductance............................................10 H
Output DC Current...........................................225 mA
Output DC Voltage...........................................440 V