I have an old Toshiba TV, model CM905C, with vertical fold over at the
top during warm-up only. The top of the screen has 6-8 lines fold over,
that gradually creep up and disappear behind the mask 8-10 minutes after
power on. Turning the power off, waiting for a while, then on again,
starts the same process over. I have checked voltages from the AC power
supply to the horizontal and vertical sections and found them to be
stable during and after warm-up. I have bridged various electrolytics in
and around the horizontal and vertical sections with no affect or change
in symptoms. I do not have a circuit schematic, so would welcome any
suggestions on how to isolate the fault. The picture is otherwise great,
good colour, good contrast, good focus. My concern is that something is
about to breakdown and I would prefer to fix it now. Thanks in advance
for any suggestions.

Wally