The 451U full wave rectifier is mounted on a B4 base and from the picture it can be seen that the cathodes are indirectly heated. The cathodes are connected to the heater supply, but the use of an oxide coated cathode will confer a greater emission for a given heater power than a directly heated valve.

The 451U was designed for low voltage battery charging service.

The classic envelope is 51 mm in diameter and, excluding the B4 base pins, is 124 mm tall.

 
Pin Connections

B4	1	2	3	4
	a(1)	a(2)	f	f

 
Absolute Maximum Operating Conditions

Rectifier	Vh	Ah	Va	mAa
	1.9	2.8	50	1,300

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 February 2008 {find valves by name}