Hi, i'm new here and sorry 4 my poor english, first of all this long flame seems to me much
out of site (? exagerate..?), too much word maybe for a very simple problem, i'm not a tech
but from the first agree with talks of J.Liebermann, the strange thing i spect from somone that
suspected the main 5v line that ususally supply the graphic/video chip, so is not (for me) a bad
idea to test the 5v line on the psu connector to the v.board since you don't found any bulged/
dirt capacitor, and if you find the v changes according to the fades then go to order caps, if not
try at least to measure on the regulator on v.board to see if exit 3,3v fixed or some like it.
I don't agree to what said, it's a luck that you have 2 equal monitor so in the last if you don't
find culprit you can swap boards and see

bye bye.