Michael Black has brought this to us :
On Sat, 31 Aug 2013, John G wrote:

William Sommerwerck explained on 30/08/2013 :
As far as I know, no monitor can be damaged by yanking the input signal.
So the "burp" while switching shouldn't be a problem.

The only way that I know of that a monitor can be damaged is if it's a
multi-sync model, and it's driven at a scan rate above its highest spec'd
rate. Other than that...

I know this is OLD History but-
The early text only green IBM PC monitors needed a sync pulse from the CPU
or they would "self destruct"
The monitor was powered from the CPU power switch so that it cold not be
left on alone.
Of course that is really long ago history. ^^

That sounds more like legend. I had a couple of Ball Brother open frame
small monitors that I used back then, for my OSI Superboard and then my Radio
Shack Color Computer. They needed a horizontal sync signal to generate the
horizontal ramp (and the very high voltage), but if there was no horizontal
sync signal, nothing bad could happen.

Michael

It is not legend.
I was very specific about which Monitor it was, text only green IBM PC
monitors ie the 5151.
I was in IBM Computer Support at the time. :-?

--
John G