N70 white screen 1.8V good and all supply good
 

some of the bb5 posible trouble is white screen usually water damage its easy to repair, just only change or jumper smps, but this time no waTER damage no drop all supply is good, it become white screen what posible damage???????????????? :confused:

Reflow glass IC display driver...this is first possible cause of white display....change ic.

try to replace the class i.c(n4200)near to keypad conector,,,or change it....good luck/