We have a Dell Latitude 5420 which had a glitching display, now the display has totally died but can be viewed with via an external monitor.   I'm getting the error code of 4 amber followed by 3 white from the power LED.  I can't find any online resources which can confirm what is causing this fault/error codes.  I've ordered a replacement LCD screen replacement cable in the first instance as it is the cheaper option. 

Can anyone shine some light on what the error code is pointing to?