K800 to K810 result screen flashing white

[66xx66xx66]

try another firmware

[k8oonad]

Use SE Tool Lite
click on repairing tab
press 2+5 while connecting.

try this for 6 to 8 times.
if not work then try pressing c
after some time your gdfs will get in mode for repairing.
after that connect your phone pressing c. then restore the GDFS (hope u created back up before)

then restore original firmware.