Quote:
Originally Posted by ohohyodafarted
I recall reading that in the very early days of designing the shadow mask tube, mask warping was an issue. Evidently if the mask heats it can distort, throwing off the purity alignment. Someone even suggested that the amount of current the mask is absorbing might even heat the mask enough to cause warping. If you have ever heated a piece of sheet metal beyond the point of elasticity, you will find that it will have warped when it cools.
This was the first non-round color tube. Due to the fact that it was not round the forces in the shadow mask are not uniformly distributed and perhaps they did not have all the mechanical bugs worked out of the mask design yet.
WE will probably never know why the purity went to heck, but it sure looked real good at the start of the restoration.
|
It should be remembered that the funnel to faceplate panel seal (with shadow mask in place) was made by some mystery process that likely involved higher temperatures than the FRIT process that was used on later color CRTS. I believe that it was very possible that the (electro seal?) process involved also could have contributed to the instability of the shadow mask observed. The usual cream-colored frit is not apparent on my CRT:
http://www.videokarma.org/attachment...6&d=1271460550
Westinghouse yields of this CRT were reported to have been low, process times were long... they likely lost money on every set they sold with the 22EP22.
jr