Panasonic TC-L42D2 Technical Manual page 86

Conclusion: Exchange the A board or TC board
Source Driver
LCD Panel (Gate Driver is in Panel)
Diagnosis
In this case , many vertical lines all over screen may be caused
by the A board or TC board.
A one vertical line defect (right photo) would be the panel.
Picture Defect (6) (D Series)
Gate
Driver
LVDS DATA
Control DATA
TC board
LVDS DATA
A board
(LVDS= Low Voltage Differential Signaling)
Sample Picture
many vertical lines
many vertical lines
Panel Defect
Slide # 86