A.K.A. snivets. The ones I remember were straight vert lines that
squiggle. Sometimes the lines are broken. Cheap horz output
tubes usually the guilty party.
On yours be sure the hoz out is not running hot first. Trouble is
the line can be from anything in the hoz, blanking, or power supply.
Also can be picking up other garbage in the house.
73 Zeno
LFOD !