IBM 5155 analogue display fault

[Jules Richardson]

Just picked up an IBM 5155 luggable which was working up until the point
the chap switched it on to show me it working, when it promptly
broke :-)

On switch on it gives a narrow horizontal band of amber about 1.5" high;
after a couple of seconds the whole screen changes to flickering amber
with brighter zig-zag flyback lines visible.

Just thought I'd quickly ask in case there's component foo that's a
common failure in these machines (I haven't even pulled the case to look
for an obvious failure yet, let alone do anything else)

ta

Jules