I have not opened the case yet. If I do without a schematic, then I may be
faced with reassembling it without a fix or leaving it apart for an undetermined
time. I would prefer a sustained effort until resolved so I will wait for a
schematic.
Since the image is perfect and undistorted in any way I would assume generally
that the power supply is not the issue. Only the image brightness is varying on
it's own with no pattern. Seems to be mostly brighter rather than darker as
images go, sometimes the changes are slow 1-3 seconds, others are more rapid.
Almost like a flickering fluorescent lamp going bad or a stream of morse code
modulating the cathode. Feels like a cold solder joint affecting the kinescope
cathode or drive. Schematic would help a lot.
