The Z90 produced by M-OV is another manufacturers implementation of the EF50. The design was used by many devices used by the UK government and subject to a CV specification and many valve makers produced valves to the specification. Government procurement could not rely on a sole supplier.

Post war the EF50 design was used in television receiver designs for the restarted television service, thus commercial production was valuable for the valve makers.

The screening can has helical scratches and this suggests that the valve has been used with a screw locking base as developed by the RAF. See EF50 for a picture of the base.

The plain aluminium can carries the Osram logo of M-OV on the reverse.

The wide metal tube envelope is 33 mm in diameter and, excluding the B9A base pins, is 59 mm tall.

References: Datasheet & ¹⁰⁴³.

 
Pin Connections

B9G	1	2	3	4	5	6	7	8	9
	h	g2	a	g3	s	k	g1	s	h

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	250	-2	10	3	1.0M	6.5

Thanks to Frank Philipse for supplying the above PDF datasheet