Toshiba 50A50 model

That sounds like an older model. It might not have a service mode for convergence, it might have a board in the front with all those pots on it.

In any case you need to examine the error critically and determine what is wrong. If any lines take a sharp bend, the STKs are clipping. If the lines are relatively straigh and just diverging there could be other causes. It could be a case of yoke tilt. For examle if the vertical lines of one color are to the left the top and to the right at the bottom, and the horizontal lines of that color are high on the right and low on the left, you got yoke tilt. You just give it a twist and you don't have to make any adjustments.

If the raster in error is bigger than the others, evidenced by the vertical lines at the sides and horizontal line at top and bottom fallid outside the others, the yoke may have fallen.

But if you have a severe error in a corner, do not try to adjust it, you have a defective STK.

If you could get up a good screenshot I might be able to tell exactly what is wrong with it, but that takes all the fun out of it.

JURB