Do it by the book either Sams or Zenith.
Keep contrast & brite DOWN, dont want it too brite.
Keep going back to the center.
I assume its an upright chassis, check the convergence PCB for cold
solder joints.
Out of the 1000's of these that came through only maybe 2 needed
repairs for conv. But anything is possable.
Its normal for the service line not to converge, you kill the
vertical pulses the conv circuit needs.
73 Zeno