The 25A6G is an audio output pentode that was designed for single ended use in universal sets. The heater is designed for series connection across the mains supply, and the anode ratings reflect the low HT available when no mains transformer is available.
The Type 43 is identical electrically but fitted with a UX6 base cap.
The classic envelope is 43 mm in diameter and, excluding the IO base pins, is 101 mm tall.
References: Data-sheet, 1040 & 1043. Type 25A6G was first introduced in 1936.
Absolute Maximum Operating Conditions¶
Updated January 29, 2013. shape:classic construction:pinch type:pentode age:1930.1940 base:io heater:300ma pins:8 pin:1.m pin:2.h pin:3.a pin:4.g2 pin:5.g1 pin:6.- pin:7.h pin:8.k