I will be happy to assist you with this question.
On the newer CRT models-after 1995 or so,there is no more vertical hold adjustment available!
There is a crystal oscillator for the horizontal frequency,then inside of the jungle chip,this frequency is divided multiple times until reaches 60 Hz.This 60 Hz frequency will be used as a vertical hold frequency!
Then the pulse from the flyback transformer is used to sync the oscillator inside of the jungle chip(croma IC).
If you do have a vertical jitter,or picture is rolling,the problem it will be the jungle chip IC(croma IC) -IC601 on the board or the circuitry around it.
This IC is a surface mounted IC,requires highly skilled and trained tech to replace it-
64 pins on about 1 square inch IC.
The only adjustments available in the service menu are for vertical size and position-no hold!-picture should be "hold " automatically.
I hope this helps,