Normally replaceable-slightly different:
3AX81 Different maximum ratings:
AC128; AC153; AC188; AC193
First Source (s)
Mar.1957 : Valvo-Berichte
-: Solid State /
PNP germanium alloy transistor intended as driver / small power amplifier / universal purpose; all-glass body with heat sink. Red dot indicates collector.
Also made by Philips and related manufacturing plants. Text in other languages (may differ)