The R18 is a high performance single rectifier with an anode voltage of 625 Volts. At these voltages a full wave rectifier configuration is easier to implement with two valves rather than a pair of valves in a single envelope.

The rated reservoir capacitor is 24 µF and to limit surges the circuit series resistance needs to be at least 250 Ohms.

See also The Mullard EY84 which is very similar.

The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 74 mm tall.

References: Datasheet & ¹⁰⁴⁰.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9	tc
	ic	ic	k	h	h	ic	ic	ic	ic	a

 
Absolute Maximum Operating Conditions^¶

Rectifier	Vh	Ah	Va	mAa
	6.3	1.15	625	125

Thanks to Frank Philipse for supplying the above PDF datasheet