The U151 is a wire-ended EHT rectifier with a 6.3 V 90 mA heater which is normally fed from a well-insulated winding on the line output transformer of a television receiver. This is the original design of TV EHT rectifier, which in 1948 made the AC/DC technique possible in the television set. Previous EHT rectifiers worked to a few kV but for magnetically deflected television displays much higher acceleration was required and thus higher EHT.
The oxide coated cathode tube is just visible within the anode bell.
A better view of the envelope lettering.
The thin glass tube envelope is 14 mm in diameter and, excluding the base wires is 53 mm tall.
References: Data-sheet & 1040. Type U151 was first introduced in 1952. See also1952 adverts.
