The Type 43 is an audio output pentode that is designed for use in receivers with a series heater chain. It is electrically identical to the IO based 25A6. The valve is rated for use in low power single ended output stages.

The classic envelope is 44 mm in diameter and, excluding the UX6 base pins, is 106 mm tall.

 
Pin Connections

UX6	1	2	3	4	5	6
	h	a	g2	g1	k	h

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout	D
	25	0.3	160	120	-18	36	12	42,000	2.4	2.2W	10%

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 10 March 2008 {find valves by name}