DuMont 12JP4 CRT observations

[Tom Albrecht]

Looking at two different DuMont 12JP4 CRTs I have, there are some obvious differences in the envelope construction. I'm curious how prevalent the two styles are. In some ways it's surprising that two tubes with such differences have the same number, without even a suffix change.



The one on the left is from a DuMont RA-103 Doghouse, and the one on the right is from a Crosely 9-407 (RA-103 clone).

Note that the original etched DuMont labels are more or less identical. Here's the tube without the bulge (the one on the left above):



Here's the one with the bulge (the one on the right in the image above):



Not only do the two tubes have slightly different overall length, but the yoke position between the two is slightly different, which is clearer to see via the red reference lines I added to the picture. Both the Crosley and DuMont chassis (which look identical to me) have two sets of mounting holes for the yoke, which I suspect is to allow for the slightly different lengths and yoke positions of these two tubes:



You can see in the above picture that the yoke could be moved forward to a new sets of mounting holes that is visible, in addition to being able to slide the yoke back and forth a little for each set of holes.

I think the one on the right is a Pyrex tube, while the one on the left may be soft glass. The one on the left is heavier, and appears to have somewhat thicker glass, at least on the front face.

Which of these two types do the rest of you see in your DuMont and DuMont clone sets?