Unstable vertical hold and buzzing on sound on tv

The tv is a Contec colour tv. Picture is randomly unstable
vertically and a buzzing noise is superimposed on the sound.
This happens as soon as the tv is switched on. The symptoms are:
holding for a few seconds and then fast rolling; sometimes stopping
and holding halfway with a half inch gap separating the top and bottom
of the picture running across the centre of the screen with what I'd
call 'noise' in this gap - thousands of white flecks filling this half
inch gap (don't know if that's normal, but it looks as if it is
associated with the buzzing coming out of the speaker).

I have checked for and fixed bad connections and also replaced the
vertical sync IC without effect.

Any suggestions for further troubleshooting the faulty component very
much welcomed.

Martin

 

Martin, you might want to now focus your attention on the PS........ check
the electrolytics for high ESR and replace as needed....... also check and
replace if necessary the regulator.