Westinghouse H22T155

[ohohyodafarted]

The fact that you had beautiful purity in the beginning lends credence to fact that the shadow mask was in the proper alignment when you started working on the set.

Unless the shadow mask got permanently magnetized the purity should have stayed very good provided the mask did not warp.

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.