Same function (full-wave rectifier, 6.3V heater, 70mA) but B7G miniature base — not pin-compatible with Octal
Electrical Specifications
Absolute Maximum
Anode Voltage (max)AC Voltage per Plate (max RMS)325V
Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)450V
Rectifier
Peak Inverse VoltagePeak Inverse Voltage1,250V
Voltage Drop (typical)Voltage Drop (at 70 mA)22V
Notes
Indirectly heated (unipotential cathode on pin 8, separate from heater on pins 2 and 7). Unlike directly-heated rectifiers such as 5U4G or 5Y3, the 6X5 can share a common 6.3 V heater winding with signal tubes because heater-to-cathode insulation is rated at 450 Vdc.
Maximum DC output current is only 70 mA — significantly lower than 5-volt rectifiers like 5U4G (225 mA) or 5V4 (175 mA). Verify total B+ current draw before substituting.
The 6X5 was historically prone to internal short circuits between heater and cathode, especially early production units. Later GT and GT/G versions improved reliability. Use a fuse or current-limiting resistor in the B+ line as a precaution.
5852 (Bendix) is a ruggedized military-grade version — electrically identical but built for extended life.
6Z5P (Russian) and 6C5S (Russian) are functional equivalents but may have slightly different internal construction. Pin-compatible.
Brans lists 6AX5GT as equivalent; it has slightly different heater warm-up characteristics but same electrical ratings and Octal pinout.