5B/251M @ The Valve Museum

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5B/251M

Sensibly equivalent^¶ to:

5B/254M CV428

See also:

Beam Tetrodes and the 807 - STC 5B/254M, 5B/255M, 5B/257/M & 5B/258M Advert - STC 5B/254M, 5B/255M, 5B/257/M & 5B/258M Advert

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STC G8LSD Valve Collection

The 5B/251M construction dates this valve at the commencement of the process that ended with the all glass miniature valves by the late 1940s. The pins are short and set into a glass disc base and are placed equi-spaced around the pin circle circumference. The seal is concealed within the spigot. The grids are made of thin wire on the usual notched rods. The cathode tube is flattened to an oval, the valve is a beam tetrode. The anode is brought out to the top cap.

In use other members of this series are power valves for audio or transmitter RF to the HF bands. The 5B/254M is a miniature version of the 807.

The wide glass tube envelope is 28 mm in diameter and, excluding the B8B base pins 85 mm tall.

References: Data-sheet & ¹⁰⁴⁰.

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 PDF datasheet.

Updated February 18, 2013.

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