(This is jeopardy-style; I found the answer eventually, but it is not what I expected. Posting here for search etc).
I have a Dell laptop and external monitor (on DisplayPort). It was fine for ages, but recently it has started cutting out randomly, displaying "no signal". Turning the monitor off and on, or disabling and re-enabling via Windows both make it work again, but it is annoying and disruptive.
To investigate, I've disabled all the power settings / screen-saver / etc, so it shouldn't be the OS disabling it electively.
What might cause this? And how can I fix it?
Best Answer
This could simply be a cabling problem. Check that your video cable doesn't run too close to anything like a power pack, or something else that could cause interference to the signal.
OK; since I'm the OP I'll elaborate: the DisplayPort cable had slipped, and was directly next to my (powered) USB hub. Simply relocating the cable solved the problem completely. I guess with a digital signal, some kinds of interference can have a significant effect, requiring a signal reset.