The delightful Type 717A is known as a 'little doorknob' (for the doorknob see 703A). Intended as a low-noise front-end amplifier in UHF radar receivers, the 717A achieves 4 ma/V despite its small size. Designed by Western Electric, the 717A was made in large numbers by several US manufacturers during WW2. It was a successful valve although it was soon superseded by improved (and cheaper) all-glass types.

In the John Lawrence collection are two of these valves, one is marked as a microwave triode and the other as a VHF triode.

See also VT269 under close inspection it is clearly a pentode.

The balloon envelope is 34 mm in diameter and, excluding the IO base pins, is 37 mm tall.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	s	h	k	g1	k	g2	h	a

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.175	180	120	-2	7.5	2.5	0.25M	4.0

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 09 February 2008 {find valves by name}