Prima PS-42D8 B Service Manual page 23

Check if the socket between Y driving board and Y BUFFER is plugged well. If not, plug it well. If yes
then replace Y BUFFER (upper, lower) in respect to the upper , lower part of the dark line on the
screen.
3.There appear on the screen one or several horizontal lines that are much brighter than the remaining
horizontal lines at the edge:
Check if the socket between Y driving board and Y BUFFER is plugged well. If not, plug it well. If yes
then replace Y BUFFER (upper, lower) in respect to the upper , lower part of the dark line on the
screen.
4.There appear on the screen one vertical unlit line or a vertical entirely unlit block
a. If it's one vertical unlit line, then COF has problem.
b. If it's a vertical entirely unlit block, then first check if the connection socket between COF and
logic BUFFER has problem. If not, check if the connection socket between the logic BUFFER
and the logic board is normal. If yes, replace the logic BUFFER. Finally, if the problem still
remains when the replacement is over, then replace the logic board.
5.There appears on the screen a mono color signal and one or several vertical bright lines of other
colors:
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