The last issue that needed attention was the lack of sufficient width in the raster. This is an unusual problem, since most sets I work on have too much overscan, and it takes some creativity to get the raster down to the correct size for the CRT mask. I think the manufacturers figured out pretty early that customers seldom complain about overscan, but will surely complain if the raster doesn't quite fill the screen. Perhaps the 621TS was engineered before manufacturers came to that conclusion.
No setting of the horizontal drive, linearity, and width controls would give me a big enough raster. Just a tiny bit too small -- not off by a mile. I checked all the components in the horizontal deflection system, and replaced some out of tolerance resistors, but there was no improvement.
What worked in the end was to change the tap on the big damper resistor in the HV cage. RCA specifically provided extra taps on this resistor for adjustment of horizontal linearity. I found that the lower resistnace tap reduced the size of the raster, and the high resistance tap increased the size of the raster. The linearity coil needs a little touch up after changing that tap, but overall, with proper adjustments, the high resistance tap gives a slightly larger raster.
This is the resistor in question:
After optimal adjustment, the overall raster linearity, both vertical and horizontal, is pretty good:
Not perfect, but pretty good for a tube TV. Many later models cannot do this well. The only ones that routinely beat this are DuMonts.
So we'll consider this set done.