Question Monitor is the culprit?

[kryo92]

So, it started with my mom's pc booting up but video output was not following (W10 booted fine, since start up notification were sounding off).
It showed picture 15 minutes, 30, an hour or after a couple of hours, just at random.

I unistalled old drivers, installed new ones, reinstalled OS, nothing. It wasn't software.

Changed VGA cable, checked all pc connections, components, finally took it to service and they reported malfunction in motherboard.

Since it was old pc, ordered a new one, pretty basic config for her, today it came, connected all and again, nothing on the monitor (sometimes just some shade of black)

Is it safe to say monitor is faulty? I don't have anyone to take it to try, but it should be the culprit, I mean brand new pc now but same old problem.

It's almost 10 years old LCD one...

 

[kryo92]

Update about monitor...

When the pc is on and monitor is black, actually only part of it seems it's completely black, but in pitch dark room if I shine a light on it I can see black portion consisting of small black spots, lines, like web, that changing and slowly dissapering when I turn off the monitor.