The 866 is a half wave mercury vapour rectifier on a UX4 bayonet base. The mercury on the inside of the glass obscures the electrodes.![](../pics/aaq0670a.jpg)
Here the supports for the cathode can be seen. An image of the inside was not possible, however, looking inside revealed a circular corrugated cathode supported at the ends and the centre. Above the cathode was a gap and the anode, supported only from the top cap, is a flat disc.The classic envelope is 60 mm in diameter and, excluding the UX4 base pins, is 143 mm tall.Reference: Data-sheet. Type 866 was first introduced in 1938. See also 1938 adverts. |