I dont know about lolly pop tubes but THINK the beam is scattering &
not hitting the screen directly. On many sets @1975 this could happen
A vert out would short
DC got on the yoke
This caused the beam to shift off the screen & you would get
a dim blank foggy pix. from the scattering. When you turned it off
you would see a flash with a vert problem, either missing the
bottom or top half for a second.
73 Zeno
LFOD !