Connecting a monitor with the power on

[Daniel Prince]

I am having a problem with my monitor turning itself off. Sometimes
it will turn itself back on. (I know that it is not a screen saver
because I do not use the blank screen saver and the power LED goes
out.)

It would be much easier for me to figure out what is wrong if I
could connect and disconnect the monitor cable without turning my
computer and monitor off but I do not know if this is safe. Is it
safe, or do I have to power everything down first? Thank you in
advance for all replies.

 

[Guest]

I am having a problem with my monitor turning itself off. Sometimes
it will turn itself back on. (I know that it is not a screen saver
because I do not use the blank screen saver and the power LED goes
out.)

It would be much easier for me to figure out what is wrong if I
could connect and disconnect the monitor cable without turning my
computer and monitor off but I do not know if this is safe. Is it
safe, or do I have to power everything down first?

It's better to power down everything first, but if you decide not to,
the risk is probably greater to the video adapter than to the monitor,
so at the very least don't use your expensive video card while doing
this.

When the monitor is disconnected from the computer, does it either
display "NO SIGNAL" on the screen or allow you to bring up the
on-screen menu? If so, then the problem is almost surely with the
computer, unless the video cable or connector is bad, but the latter
should result in a flickering or jumping picture when you wiggle them.

Never ever let your brain explode. It's VERY bad for you and
it leaves a terrible mess for someone to clean up.

Thanks for the warning. I think you saved my life.

 

[paulmd]

I am having a problem with my monitor turning itself off. Sometimes
it will turn itself back on. (I know that it is not a screen saver
because I do not use the blank screen saver and the power LED goes
out.)

It would be much easier for me to figure out what is wrong if I
could connect and disconnect the monitor cable without turning my
computer and monitor off but I do not know if this is safe. Is it
safe, or do I have to power everything down first? Thank you in
advance for all replies.

Go for it. It's not exactly recommended practice, but the potential for
harm is minimal. Just don't make it a habit.

 

[DaveW]

No, that is NOT safe. You can get arcing and fry them both.

 

[Guest]

No, that is NOT safe. You can get arcing and fry them both.
If it's a DB15 vga setup, make sure to insert and remove the
connector straight in and out without touching any of the pins
to the shell. I've seen arcing on more than one occasion. It
didn't seem to hurt anything though. Just lucky, I guess!

 

[Paul]

I am having a problem with my monitor turning itself off. Sometimes
it will turn itself back on. (I know that it is not a screen saver
because I do not use the blank screen saver and the power LED goes
out.)

It would be much easier for me to figure out what is wrong if I
could connect and disconnect the monitor cable without turning my
computer and monitor off but I do not know if this is safe. Is it
safe, or do I have to power everything down first? Thank you in
advance for all replies.

I share a 17" LCD monitor between two computers, without a
KVM. I have disconnected and connected the VGA connector
probably hundreds of times. The monitor still works, and
is what I'm typing this on.

I also had a Sony Trinition CRT monitor (retired, but still
working), but for that one, I used to be nice to it, and
switch it off before moving the connector from one computer to
another. I didn't switch off the computers in that case. The
computers still had active video output signals, while I was
switching the connector.

While modern multisync monitors are reasonably well protected
(they measure the H,V drive for compliance with the accepted
range of H and V frequencies), there is still a tiny interval
where the disconnect transient is fed to the monitor. I wimped
out in that case, and turned off the monitor, not knowing whether
sooner or later I'd get an ugly surprise. With an LCD, there
is no flyback or resonant circuit to worry about - signal
treatment is digital, and cannot be harmed by how "wobbly"
the logic 1's and 0's are. I feel much less concerned hot-plugging
the LCD. But I am careful to make sure the shell is aligned well,
before fully inserting it. I don't just blindly stab the
cable connector at the back of the computer

For a bit of trivia, I did find a datasheet for a protection
device that could be used by a monitor maker. What I learn
from this document, is they are mainly concerned about
static electricity contacting the signal pins on the VGA
connector. Another important aspect of this device, is
"backdrive provention". A diode on pin 1 (VCC), prevents
an active video card, and a switched-off monitor, from
causing current to flow through the ESD diodes and into
the VCC of the monitor. I expect every monitor has taken
backdrive into account. The moral of this doc, is don't
handle the pins on the VGA connector, while skuffing
across the floor.

http://www.cmd.com/products/data/pdf/cm2006.pdf

Paul

 

[Mike Walsh]

You probably won't find a monitor or PC maker that recommends plugging and unplugging the video cable with power on, but many of us have done it many times without any problem.

 

[meow2222]

You probably won't find a monitor or PC maker that recommends plugging and unplugging the video cable with power on, but many of us have done it many times without any problem.

If monitor and pc chassis are both earthed (grounded) via the mains,
there wont be a problem. This is normally so with CRTs, though there is
a known IEC connector fault that can result in no earth. None of my
LCDs are earthed, so I wouldnt want to do it with those. To improve the
odds I always touch the outers of the plug/skt together before
plugging, so if there no earth any static will be discharged. But for 2
core mains lead appliances, always unplug mains first.


NT