Help with Sony trinitron monitor

Recently picked up 3 silicon graphics CRTs, two of them only have serial out/13w3 but one has VGA 15w out and as I test it, the image is no bueno.

Any idea what might be causing the problems? I’m not scared to open it, I’ve been repairing devices for a while, I understand there’s gotta be extreme care due to the high voltage but I’ve done my fair amount of fooling with electronics. Just want to see if anyone’s got a solid idea to tackle those things first. Thanks!