The UR1 is a half wave power rectifier on a continental Ct8 base and dates from 1934. The data manuals from 1950 only list the UR1C on a British B5 base. The Ct8 was not popular in the UK in spite of achieving good sales in Europe.
The anode is made of mesh and the cathode is quite long compared to sensibly equivalent valves such as the 1D5.
The series resistance has to be a minimum of 125 Ohms for this rectifier and the reservoir capacitor should not exceed 32 µF.
Mullard replaced this rectifier in 1939 with the CY1 (Ct8) and CY31 (IO).
Side view.
The dome carries the Mullard name and the Type designation. The cathode tube is reduced to a spike for passing through the top mica.
A clearer view of the dome etching.
The classic envelope is 42 mm in diameter and, excluding the Ct8 base pins, is 98 mm tall.
References: Data-sheet & 1043. Type UR1 was first introduced in 1934. See also1934 adverts.
