The 35Z4 is a half wave rectifier and was designed for television use. It would feed a 40 µF reservoir capacitor through an effective series resistance of 100Ω.
The green horizontal stripes are all that is left of the F logo of Ferranti. SeeHL22 for a clearer logo. Below the stripes is the remains of the name Ferranti with only the E being distinct.
The anode is wide and almost flat, the working area is the small cylinder at the centre.
The anode edge on.
The lower mica, the heater is thickly insulated and passes through the cathode tube four times. Heavy insulation would have the effect of slowing the heating of the cathode, in effect a time delay to allow the other valves to reach operating temperature before the HT was applied. The HT would then not rise to the peak of the mains cycle and lower rated components could be safely used.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 79 mm tall.
