12AX4

Rectifier — Octal

Known Equivalents & Substitutes

12AX4GT12AX4GTA12AX4GTB

Similar Tubes (Not Drop-In Compatible)

6AX4GTA

Identical damper diode except 6.3V heater instead of 12.6V — same PIV and current ratings

Full-wave rectifier on Noval base with 6.3V heater — similar TV rectifier service but different base and full-wave vs half-wave topology

Electrical Specifications

Rectifier

Peak Inverse VoltagePeak Inverse Voltage4,400V

DC Output Current (max)DC Output Current (max, boost rectifier)125mA

Peak Anode Current (surge)Peak Output Current750mA

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.6A

Notes

TDSL lists 12AX4GT as a different-rating variant, and 6AX4GTA as the 6.3V heater version.
The GTA and GTB suffixes indicate improved glass envelope designs with the same electrical ratings.
Half-wave damper diode — used to recover energy stored in the horizontal deflection yoke inductance and boost the B+ supply voltage.
Peak inverse voltage of 4400V handles the flyback pulse generated during horizontal retrace.
Peak output current of 750 mA; DC output current rating is 125 mA in boost rectifier service.
Heater-cathode voltage rating is critical in this application — cathode operates at high positive potential relative to chassis ground.

Pin Layout — Octal

1No Connection

2Heater

3Plate

4