WHAT CAN YOU TELL ME ABOUT THE MAZDA VALVE NUMBERING CODE?

Well, Mazda were another manufacturer who wanted to stand out and indeed made their own version of the Octal base with a fatter spigot known as the Mazda Octal or MO base.    Their valve numbering system was a bit kooky too and needs some explanation. 

The typical Mazda valve type number was an alphanumeric affair comprising of; a numerical prefix followed by a letter which in turn was followed by a mumerical suffix.

The numerical prefix always indicated the heater voltage EXCEPT where 10, 20 & 30 were used which indicated the heater current draw in 0.1A.  A further exception was for rectifier valves whose designation started only with a letter - eg U31, UU5 etc.

The letter indicated the valve type with letters allocated as per the following table.

The numerical suffix was a sequentially assigned development number.

Here are a couple of examples: -

UU5 -  the 5th full-wave rectifier developed by Mazda.

20P1 - the 1st 200mA  heater output pentode developed by Mazda.