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
in the second sentence, i meant to say:
flickering--very quick alternating between backlight fully on and then dim but not off; flashing--quickly alternating between backlight fully on and fully off
Attach an external monitor -- if it displays OK, no flickering -- chances are it's the display panel that needs to be replaced. If it flickers as well, it's the GPU -- meaning a replacement mainboard is needed.
Reseat the LCD cable and check.
If you know the right part# of the system configuration - you can find the LCD cable here - http://bit.ly/2d31ie1
If not, then as advised by ejn63, either the LCD assembly or the motherboard needs to be replaced.
Also, please click my DELL-username and write me a private conversation with the service tag and your contact details(Name and Email) for case records.
Let us know if you have any other queries.
graphics work properly on an external monitor.
i will re-seat the LCD cable but i did that yesterday when i replaced the DC-in jack thinking that might have been the problem, since plugging and unplugging the power supply affects the screen's flashing/flickering behavior.
can you confirm that the inverter is built into the display panel? i would not want to buy a new panel only to find out that the inverter is built into the motherboard.
These systems do not use CCFL backlit screens -- there is no inverter (the backlight is LED and built into the display panel).
No one can guarantee you that it's the screen that's faulty - but it's the next part to replace. If it does not solve the problem, it's a video chip issue and the mainboard would need replacement.
thanks for confirming that there is no inverter.
both the vga and HDMI output are flawless, mirroring the display while the display is doing its flashing/flickering/dimming thing. i conclude that it's not the gpu.
i think i will try an LCD cable before replacing the display. $4 vs $50 so worth the gamble IMHO.