[ICOM] IC781 display problem

[Doug Grant]

My 781 has developed an annoying problem with the display.

Sometimes on power-up, the display is compressed to a total height of
about 3/4-inch, and jumps up and down like an old TV with vertical
hold out of adjustment.

Other times, the display is the right size, but the brightness jumps
between two levels.

Before I go digging too far, I thought I'd ask this group - has anyone
seen this before? Is is a CRT problem, power supply problem, or
something (or things) else?

73,

Doug K1DG