RCA B&W TV KCS113A horizontal nonlinearity problem

[wa2ise]

This is my RCA B&W set from 1958, in Sam's folder 398 folder 3. Have it working well, *except* for a somewhat visible vertically oriented bighter bar up and down the middle of the screen. Caused by a small area of non-linearity in the horizontal deflection. The deflection slows down some, allowing more electrons to hit that section of phosper in the middle than in other areas (for a constant flat video image). On the back page of the folder, there is an adjustment for removing this "white line" by adjusting the Horizontal drive trim cap. This reduces it some but not eliminates it before the horizontal losses lock.

The set has been totally recapped. Any ideas? It's not too bad, but would like to improve it further.