when i boot my E6420 with AC adapter connected, the backlight doesn't come on. (i can see the screen image with a flashlight so the LCD is working).
with the computer booted, when i remove the AC, the backlight comes on at full brilliance but it flickers and flashes. (flicker--very quick dimming; flickering--very quick alternating between LCD on and totally off).
then when i reconnect AC, the screen dims to the level it would be on battery (dimmer than on AC) but still flickers--but the flashing is gone.
if i boot with AC not connected, the backlight works properly for about 10 seconds, then the backlights flashes between on and off every 1/2 second. after a couple of minutes, the frequency of the flashing on/off goes to a couple of seconds, and when it is on it flickers. so---flicker flicker flicker flash off flicker flicker flicker flash off etc.
i ran the pre-boot diagnostics. it flags the LCD cable as bad, but the display is passed as OK. I can easily replace the LCD cable, but any other ideas?
i thought maybe the DC in jack/cable was bad, but i replaced that to no avail.
thanks in advance
ken