What Happened to 15AP22 Through 15FP22?

[kx250rider]

I remember reading someplace, that a second letter in the sequence (in CRTs following bottle diameter) meant it was a better design tube. (i.e. 21YP4 vs. 21FEP4, etc)

So the string for a 21AXP22A would be:

21 ____________ AX________________________P22___________A
Bottle size_______Tube model Type_____________Phosphor type__"A" = aluminized

Charles

[WISCOJIM]

Originally Posted by kx250rider

I remember reading someplace, that a second letter in the sequence (in CRTs following bottle diameter) meant it was a better design tube. (i.e. 21YP4 vs. 21FEP4, etc)

So the string for a 21AXP22A would be:

21 ____________ AX________________________P22___________A
Bottle size_______Tube model Type_____________Phosphor type__"A" = aluminized

Charles

I knew that the "A" often referred to the aluminized bell inside the B&W CRTs, but didn't think that's what it meant for color CRTs, so I just looked it up.

The data sheets indicate the difference in the 21AXP22 and 21AXP22A is the addition of a high resistance coating inside the neck of the tube to eliminate the need for the external resistor between the CRT and the anode power supply. A high-resistance coating certainly wouldn't be made with aluminum.

http://pdf.datasheetarchive.com/inde...s-00173622.pdf

I'm also not sure the first part of what you're trying to say in your post is either clear or correct.

.

[kvflyer]

And somewhat OT, the "A" in a vacuum tube could mean controlled warmup filament, or less microphonic, or higher voltages. I guess it would be too much for us to expect some kind of order !