Re: Screen flashing
It was clearly an honest and reasonnablke mistake. That's part of the reason I did not make any joke. People we interacted daily had some sort of verbal, non-official, "checklist" before calling for help, and checking plug was on it. The doctor did not think to check to connection bertween PC and screen (he did check the power cord).
The reason I'm still thinking of it as funny is because of his face when I looked at the back of the screen, checked the plug, put it back and said "done". While I was happy to get this problem quickly finished, he was the one feeling stupid.
On a side note, if I had not found a problem with the plugs/cord/connexion, my second option would have been to get him a spare screen and tell him to call hotline in the morning. I had zero knowledge in cathodic screen inner wortking, except that this was dangerous, I knew just enough to known I was out of my field.