The U22 is an EHT rectifier, probably designed for oscilloscope type applications. The ratings of 5,200 volts and 1 mA define it for small screen CRT service.

The series resistance of the feed circuit has to be at least 50,000 Ohms and the reservoir capacitor is specified as 0.1 &mu:F at most. In the 1960s I built an oscilloscope power supply and the 5000 Volt 0.1 μF capacitors were in aluminium tube cases about 25 mm diameter and 130 mm tall. The top was an insulated cone with a central connector. The case was the second connection.

Internally the valve has a wide bell anode that shields the cathode at its centre. The enclosed construction is to minimize the emission of X-rays.

The oxide coated cathode is threaded by the heater. They are connected together at the anode end. Note the rigid cathode support wire.

The wide glass tube envelope is 27 mm in diameter and, excluding the MO base pins, is 79 mm tall.

 
Pin Connections

MO	1	2	3	4	5	6	7	8	tc
	h,k	ic	ic	ic	ic	ic	ic	h	a

 
Absolute Maximum Operating Conditions

Rectifier	Vh	Ah	Va	mAa
	2.0	2.0	5200	1.0

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}