The 5B/254M miniature beam tetrode has the same ratings as the classic 807. The difference in size between the 807 and this valve shows the extent to which valve technology matured during WW2 and the effect of the introduction of the pressed glass base. This particular base was the earliest to be developed with eight equi-spaced pins and an external metal collar to hide the envelope seal and provide a locating spigot.

The valve is also very similar to the STC 5B/251M and electrically identical to the 5B/255M. The latter has the anode connected at the base and one less connection to the cathode.

The wide glass tube envelope is 30 mm in diameter and, excluding the B8B base pins, is 85 mm tall.

 
Pin Connections

B8B	1	2	3	4	5	6	7	8	tc
	h	k,bp	g2	k,bp	g1	g1	k,bp	h	a

 
Absolute Maximum Operating Conditions

Beam Tetrode	Vh	Ah	Va	Vs	Vg	mAa	mAs	Pdriv	Pdiss	Pout	freq
	6.3	0.9	600	250	-45	100	8	0.3W	25W	40W	60MHz

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 July 2007 {find valves by name}