Normally I got everything earthed using 3 pin mains connectors,
but last night I was in a hurry checking two new monitors,
and in the hurry I forgot to check for earth connection to the monitors !
my pi3 is connected to audio equipment via jack connector, and that stuff is correctly earthed,
so when plugging in the DVI end of the cable to monitor, I saw sparks from metal parts when inserting,
after this digital video out was fried, picture looked really bad, full of digital noise all over,
the rest of the pi works, and can be used in head-less projects, like audio players.
(No monitors was killed during this experiment)