This is an elegant valve well designed for its purpose of medium power RF amplification. Within the envelope are two beam tetrodes with a maximum anode dissipation of 40w

Following the European pattern, a central flat cathode is surrounded by a split control grid (one half per valve), a common screen grid is wound next. The the tops of the beam forming plates can be seen. The anodes are finned for good heat dissipation and clearly separated from the central structures, the anodes are brought out to pin like top caps.

The heater is centre tapped to allow for 12.6 or 6.3 volt operation.

In use the designer would take care to keep the grid circuitry below the chassis with the anodes being connected to circuits remote from the input. This way undesirable feedback could be avoided.

The european design of internal capacitors for neutralisation is incorporated. Such neutralisation prevented parasitic oscillations during operation in a well designed layout.

The wide glass tube envelope is 40 mm in diameter and, excluding the B7A base pins, is 72 mm tall.

 
Pin Connections

B7A	1	2	3	4	5	6	7	tc	tc
	h	g1(2)	g2	k,bp	hct	g1	h	a	a(2)

 
Absolute Maximum Operating Conditions

Tetrode	Vh	Ah	Va	Vs	Vg	mAa	mAs	mAg	Pdriv	Pout	Pdiss	freq	f.max
	6.3	1.8	600	250	-80	200	18	7	3W	90	40W	275	486

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 21 October 2008 {find valves by name}