The Pen25 battery output pentode from Mazda was designed for domestic broadcast receivers. The filament was to be run from accumulators and the 0.15 Amp filament current would have assisted in prolonging the accumulator life.

The British domestic radio industry was converted to war production during WW2 and, much to BVA's distress, the floodgates were opened to the import of American technology and equipment. Immediately after the war Mazda tried to turn the clock back to the 1930s and re-build a distinctive British domestic market in which Americanism would find no toe-hold. All other BVA members accepted the inevitable and set about making valves of essentially American design, supplying characteristically British types (if at all) for replacement purposes only. The Pen25 is one of Mazda's post-war anachronisms. Not only was it obsolete in concept, since it was oversized compared to the B7G types by then available for all-dry portables and there was little market for new 2V battery 'household' radios, but it was fitted with the new Mazda Octal base which made it incompatible with anything else, including the American International Octal which everyone else was using. This was the beginning of a slow decline in the fortunes of the one-time British market leader.

The filament is three inverted V's. The anode is a bright oval cylinder. The suppressor grid is an oval to match the anode, but the inner grids are nearly flat across the filament.

The classic envelope is 30 mm in diameter and, excluding the MO base pins, is 70 mm tall.

 
Pin Connections

MO	1	2	3	4	5	6	7	8
	f(-)	-	a	g2	g1	-	-	f(+)

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout	D
	2.0	0.15	120	120	-3.6	5	1	0.35M	3.0	0.4W	16%

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 10 June 2007 {find valves by name}