Samsung PS-42VPS42V4SXXEU picture fault (red fog)

[fix2003]

this set get a red fog apear from the bottom full width  comes and goes
sometimes flashes
sometime only 30mm high. some time nearly full height of screen (see picture)
tv program can be seen behind this red fog
if i scart out to second tv the set has perfect picture

not done much with Plasma where do i look ???