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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 WWII. It was a successful valve although it was soon superseded by improved (and cheaper) all-glass types.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 VT-269 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.

References: Private Communication.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.