3DB3 Tube — Datasheet Summary

(Half‑Wave Vacuum Rectifier for Color TV High‑Voltage Supplies)

The 3DB3 is a heater‑cathode high‑voltage rectifier diode designed for generating the 25–30 kV needed by CRT anodes in color televisions. It includes X‑radiation shielding and was engineered to meet strict safety limits.

Key Electrical Characteristics

(All values from manufacturer datasheet)

Heater

• Voltage: 3.15 V AC or DC

• Current: 0.245 A

Interelectrode Capacitance

• Plate → (Heater + Cathode + Shield): 1.5 pF

Voltage & Current Ratings

• Maximum inverse plate voltage: 38,000 V

• Average DC output voltage: 30,000 V

• Instantaneous voltage drop at 7 mA: 60 V

X‑Radiation Control

• Built‑in shielding

• Additional design controls to reduce X‑ray output

Mechanical & Construction Data

• Envelope: T‑9 glass

• Base: Octal 8‑pin (B8‑118 or B8‑251)

• Top cap: Small JEDEC C1‑49/C1‑50

• Operating position: Any

• Max diameter: 1.188 in (30.17 mm)

• Overall length: 3.812 in (96.82 mm)

Typical Application

The 3DB3 was used exclusively in color television receivers as the high‑voltage rectifier feeding the CRT anode. It rectified the flyback transformer’s high‑voltage pulses into a steady DC supply.