The 4033A is an interesting valve with the electrodes inclined at 45 degrees and it was used in telephone repeaters. It was the professional version of the PA1. The valve was introduced in the mid 1930s but was difficult to mass produce and was blacklisted from use in military or essential commercial equipment in WW2.

The balloon envelope is 52 mm in diameter and, excluding the B5 base pins, is 103 mm tall.

 
Pin Connections

B5	1	2	3	4	5
	h	a	g1	c	h

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm	μ
	6.0	1.4	600	-20	170	1,670	9.0	15

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 February 2008 {find valves by name}