[Heathkit] SB-610 display

[Steve]

Hi all,

I posted this a few weeks ago on another reflector, got no response. 
Thought I'd try it here.

I need some advice regarding the display on my SB-610 monitor scope.

The left side of the displayed trace looks to be "normal." But, 
beginning about the center of the screen and onward to the right, the 
trace is segmented into distinct, closely spaced vertical lines. I have 
just recently noticed the vertical lines, not sure how long they've been 
there.

Any ideas as to why the right side of the display is composed of 
vertical lines while the left side is not? Is it normal?

Thanks.

Steve K8JQ