The type S217, is a low cost battery vari-mu RF pentode imported during the late 1930s as a replacement valve in 2V battery radios. Triotron was an Austrian firm and was at this time probably partly owned by Philips.
The ratings and pin connections match the Mullard VP2.
The performance figures are good and would enable the S217 to replace any of several BVA types with reasonable efficiency. However, all such valves were obsolescent by the late 1930s.
It has the gold external metallisation that was so popular at the in the 1930s.
The classic envelope is 42 mm in diameter and, excluding the B7 base pins, is 110 mm tall.
References: 4024 & 1043. Type S217 was first introduced in 1935. See also 1935 adverts.
Absolute Maximum Operating Conditions¶
Updated January 06, 2022.