The PX4 is one of the classic audio power triode valves and was first introduced in 1928. The filament is a single wire formed vertically within the anode cavity into four inverted V's. The grid is a single wire formed between two vertical notched rods 1.5 mm in diameter. The grid zig-zags around the filament.

The electrode system is only about 5 mm from front to back, but is 30 mm wide and 45 mm high. The classic envelope has a maximum diameter of 48 mm and excluding the B4 base pins, is 120 mm long. See also PX4

 
Pin Connections

B4	1	2	3	4
	a	g	f	f

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm	rk	rl	Pout	D
	4.0	1.0	300	-50.0	50.0	830	6.0	1000	3500	4.5	4.0

Thanks to Frank Philipse for supplying the above datasheet

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