The 220PT is a battery output pentode from the 1930s. With the correct anode load of 7500 Ohms this valve can deliver one Watt at 8% distortion.

The screen grid is taken to the side terminal.

The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 95 mm tall.

 
Pin Connections

B4	1	2	3	4
	a	g1	f	f

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	2.0	0.2	150	150	-9	19.0	4.0	-	2.5

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 09 June 2007 {find valves by name}