Cetron 3B28

This tube is a Cetron 3B28. It is a 4 pin, half wave rectifier tube.

3B28
Half-Wave Rectifier

Pinout

Mechanical Data

Bulb .......................................... Special
Base Type ..................................... 4-Pin
Maximum Overall Height ........................ 6.150 In.
Maximum Seated Height ......................... 5.530 In.
Maximum Diameter .............................. 2.063 In.
EIA Base ...................................... 4P

Electrical Data

Filament Voltage .............................. 2.5 V
Filament Current .............................. 5.0 A

Maximum Ratings (Design Center Values)

Diode
Peak Inverse Plate Voltage .................... 10000 V

Characteristics and Typical Operation

Gas
Output Current ................................ 250 mA

Info taken from here