The 2X2 is an EHT half wave rectifier. We also have the 2X2A variant in the museum.

The 2.5 volt heater indicates that it would be powered by a special heater winding of high insulation. Such a valve would have found application in oscilloscopes or in multiplier chains for higher voltages.

Our other National Union 2X2 has no mica support for the anode. This exhibit has a top support micas and grips the glass at four points.

Within the anode bell can be seen the coated cathode tube. This has a small diameter in relation to the bell as the emission required is low but the gap needs to be large to avoid breakdown when a high voltage is applied.

The classic envelope is 38 mm in diameter and, excluding the UX4 base pins, is 97 mm tall.

 
Pin Connections

UX4	1	2	3	4	tc
	h	-	-	h,k	a

 
Absolute Maximum Operating Conditions

Rectifier	Vh	Ah	Va	mAa
	2.5	1.75	4,500	7.5

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 10 March 2008 {find valves by name}