25AX4

Rectifier — Octal

Tung-Sol

Known Equivalents & Substitutes

25AX4GT

Similar Tubes (Not Drop-In Compatible)

12AX4GTA

Same damper diode family but 12.6V heater — not a drop-in due to different heater voltage

17AX4GT

Same damper diode family but 16.8V heater — not a drop-in due to different heater voltage

Identical function and pinout but 6.3V/1.2A heater — not a drop-in due to different heater voltage (parallel vs series string)

Electrical Specifications

Absolute Maximum

Heater-to-Cathode Voltage (max)Peak Heater-Cathode Voltage (heater negative)4,000V

Rectifier

Peak Inverse VoltagePeak Inverse Plate Voltage4,000V

Voltage Drop (typical)Tube Voltage Drop (at 250 mA)32V

DC Output Current (max)DC Output Current (max)125mA

Notes

Tung-Sol tentative data, May 1, 1954, Plate #3766. Short intermediate-shell 6-pin Octal, glass bulb, JEDEC 4CG basing.
Coated unipotential cathode. Any mounting position.
Maximum peak heater-cathode voltage: heater negative 4000V, heater positive 100V. Applicable where duty cycle of voltage pulse does not exceed 15% of one scanning cycle and duration is limited to 10 microseconds.
Maximum transient peak plate current of 3.0A applies to hot switching where transient duration does not exceed 0.2 seconds.
Tube voltage drop at 250 mA DC output: 32V.
Heater-to-cathode capacitance: 7.5 pF (without external shield).

Pin Layout — Octal

2No Connection

3Cathode

5Plate (Anode)

7Heater

8

References