6BX4

The 6BX4 is a miniature seven-pin full-wave vacuum rectifier with two anodes and a common cathode. It converts AC to DC in power supplies, rather than amplifying signals. Ateliers Belvu describes a unipotential-cathode type and cites RETMA release 1249 dated 30 October 1953: a specific document date, not the introduction year of every specimen. Indirect heating needs 6.3 V, 0.6 A AC or DC; Mazda-Belvu specifies parallel supply. Any mounting position is allowed.

Maximum rectified DC output is 90 mA, while peak plate current is 270 mA: different quantities, not equivalent output-current ratings. Peak inverse voltage differs by sheet: Ateliers Belvu gives design-center 1350 V, Mazda-Belvu January 1968 gives 1500 V under its average-limit system. Peak heater-cathode limit is 500 V, explicitly either polarity in Ateliers Belvu. These must not be substituted for DC load voltage, which also depends on transformer and filter.

Filter choice changes conditions. The Ateliers Belvu capacitor-input example gives 50 µF, minimum effective supply resistance per anode 300 Ω, total AC supply 700 V RMS and output 90 mA. Its choke-input example gives minimum 8 H, supply 970 V RMS and the same DC current; separate configurations. Mazda-Belvu specifies input capacitance up to 50 µF or input inductance at least 8 H, with 90 mA. Its table gives rectified voltage at filter input with capacitor from 400 V at half-load 45 mA to 360 V at full-load 90 mA; with choke, respectively 385 to 375 V. These are results under tabulated conditions, not guaranteed voltages for every supply.

The base is B7G, described as 7C10 by Mazda-Belvu. Both sources assign 1 and 6 to the two anodes, 3 and 4 heater, 7 cathode. However, 2 and 5 are no connection in RETMA/Ateliers Belvu, internal connections in Mazda-Belvu. They must not be universally treated as spare tie points. The sources also reverse the numerical names of the anodes, while pins 1 and 6 remain separate anodes.

Mazda-Belvu specifies A19-4 envelope, maximum diameter 19 mm, maximum glass height including tip above the pin plane 60.3 mm and pin projection up to 7.14 mm. Earlier Ateliers Belvu uses inches and T5½: maximum diameter ¾ inch, 19.05 mm, and base-to-bulb-shoulder height excluding tip 2 ±3/32 inches, 50.8 ±2.38125 mm. Dimensions remain separated by measured part and version. Mazda-Belvu also lists 6X4 in its heading: a correspondence stated by that document, to be read alongside its data and connections. Documentation: Ateliers Belvu, 6BX4 Full-Wave High-Vacuum Rectifier, data, curves and outline reproducing RETMA release 1249, 30 October 1953; Mazda-Belvu/CIFTE, 6BX4–6X4 Diode biplaque, January 1968.