[old_tv_nut]

Forget the HV, but is the horizontal running on the workbench? It has to be running in order to get a burst gate pulse. No burst gate, nothing gets to the phase detector, so impossible to tell what's wrong or not.

Also, is the scope set for DC coupling? The variation you are looking for is slow, same rate as the color changing a few times per second, so with your high speed scope setting and DC coupling, you would expect the trace to go up and down a few times a second, in sync with the color phase changing. If the scope is set to AC coupling, you won't see such a slow variation at all.

One more thing - if the color is changing rapidly, the voltmeter may not respond in time, that's why the scope is preferred.