The U4020 is a half wave rectifier designed for 200 mA series connected heaters as found in AC/DC radio receivers.

The reservoir capacitor can be 16 µF with an effective minimum series resistance of 47 Ohms.

The narrowness of the anode compared to its width can be seen. The cathode tube fits into a small cylindrical cavity formed by the anode plates. The side wings are for effective radiation of heat.

The dome carries all of the identification. The arrangement of micas allows the electrodes to be a push fit to the shaped envelope.

Close-up of the anode.

The anode in front elevation. The supporting rods can be seen to pass between the plates. The cathode tube is uncoated outside the anode. The heater can be seen as a number of folded sections passing through the cathode.

The classic envelope is 42 mm in diameter and, excluding the B5 base pins, is 99 mm tall.

 
Pin Connections

B5	1	2	3	4	5
	a	-	h	h	k

 
Absolute Maximum Operating Conditions

Rectifier	Vh	Ah	Va	mAa
	40.0	0.2	250	120

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 21 October 2008 {find valves by name}