The TH233 is a triode heptode mixer with a 200 mA heater for use in a series heater chain in a universal or AC/DC receiver. The TH233 has the Mazda Octal base and the electrically identical TH2321 has the older B7 base.
This is a pre-war design that was still advertised in 1948 before Mazda introduced miniature all glass valves.
The classic envelope is 32 mm in diameter, and excluding the MO base pins is 89 mm tall.
References: Data-sheet, 1040 & 1043. Type TH233 was first introduced in 1939.
Absolute Maximum Operating Conditions¶
Updated November 04, 2020.