How to Read CRT Tube Numbers

All picture tubes, whether monochrome or color types are identified by a specific code consisting of numbers & letters. The codes are different from each other because different tubes have different characteristics.

For example, a positive monitor colour picture tube may have the designation, M34AFA63X03 that can breakdown in to 6 parts: M/34/AFA/63/X/03

Part: Application

Computer monitor tubes start with the letter "M" while for a TV picture tube, it starts with "A".

Part: Screen diagonal measure in centimeters (cm)

The "34" means the diagonal viewing measure is a maximum of 34cm which refers to 14" tube, 36cm is 15", 41cm is 17" & so on.

Part: Relatives code

The letters "AFA" designate relatives of tubes that have similar physical & electrical characteristic. These letters are assigned alphabetically beginning with "AAA", followed by "AAB", "AAC" etc.

Part: Relatives number

The number 63 shows a specific tube within the relative’s code. A different number is assigned to tubes within the same relatives that have different neck diameters, for example a single digit would be a monochrome tube, but this two-digit number shows it is colour.

Part: Phosphor Type

The fifth symbol gives the phosphor designation. The letter X here corresponds to P22 for colour picture tubes. Colour monitor tubes can have any other single letter (excluding I, O, or W) to designate other phosphor type for various applications. For monochrome pics, the phosphor symbol is WW, corresponding to P4. Monochrome monitor tubes can also use WW or some other two-letter combination (excluding I & O).

Part 6: Integral neck parts

The sixth symbol is assigned only for tubes having integral neck parts, such as the deflection yoke. The specs are only applied to a specific tube manufacturer. The primary consideration here is winding inductance. The yoke coils have different sensitivity i.e. deflection per Amp in both horizontal & vertical.