My screen shakes so heavily. Please help

[IliaPreston]

I have a serious problem with my desktop computer:

Yesterday when I came home in the evening the screen saver was on, and I pressed a key twice, brought on the Windows Login screen and logged in to Windows.
As soon as I logged in, the screen was suddenly shaking very heavily, and nothing could be read.
But, after three or four seconds the shaking stopped and everything was normal again.
So, I thought it was just a fluke accident. I forgot about it.

Today, when I came home in the evening, the screen saver was on. So I logged in. As soon as I logged in, the screen was suddenly shaking very heavily again.
Just like yesterday.
But, this time it did not stop shaking after a few seconds or even a few hours.
The heavy shaking persisted.

I noticed that on some Windows screens (as opposed to applications), the shaking was very minimal.
For example when I pressed Windows Key + L to show the desktop, the desktop was shaking very little bit, but when I pressed Alt+Tab to bring on an application (like firefox or windows explorer, etc) the shaking was very heavy again.

After playing around with it, on the Background settings screen (Desktop -> right-click -> Personalize) where shaking was little, I changed the picture, and nothing changed. Then I changed the Fit from Fill to Fit, and that reduced the shaking considerably, but it was still shaking heavily, and I still couldn't work.

After playing around with it a lot, I found another screen where shaking was little (The High Contrast setting screen):
https://i.imgur.com/DHjgcnj.jpg
In there I turned on the High Contrast option, and suddenly the shaking reduced radically.
It now shakes a little bit. Sometimes just flickers
The above setting change also changed the screen to the high contrast mode which has a black background and I don't like it.
But, now even though the new high contrast mode is ugly, the computer is at least usable, and I can type this post.
Before that, the shaking was so extreme that I couldn't read anything, let alone type this post.

Other observations:

1 - On a lot of screens there are shadows. For example please see the shadow of the last three menu items in this popup menu:

https://i.imgur.com/loz5hEH.jpg

2 - On the same High Contrast screen, there is an additional setting called "Choose a theme" and by default it is set to "Unsaved theme". Please see this screen print:

https://i.imgur.com/DHjgcnj.jpg
If I change the theme from "UnSaved Theme" to any of

High Contrast #1
High Contrast #1
Or
High Contrast Black

Nothing regarding the shaking or flickering happens (The theme changes though).
But, if I change it to
High Contrast White
then the heavy shaking begins again!!!

I don't know what to make of it.

3: Specs:

My computer is Desktop 64 bit, running Windows 10, 64 bit
My monitor is a Samsung LED flat monitor that I bought in 2011, and it has been working fine all these years serving three different computers (my current Desktop computer as well as the previous two computers).

4 - Other notes:

I have checked the monitor cable connections (power as well as signal (HDMI)) on both ends, and all connections are completely tight.
Several times I have shut down my computer, unplugged everything (including monitor's power cable), waited several minutes before turning everything on again, and the problem persists.

5 - As may or may not be clear from my initial explanations above, the screen saver did not show any shaking problem, not a tiny bit.

After pressing a key to remove the screen saver, the picture screen that appeared (the pre-login screen that does NOT have a password box), did NOT show any shaking problem either.
After one more key stroke when the Windows Login screen appeared, there was little shaking (just like most other windows screens that I explained above).
As soon as I typed in the password and then Windows was unlocked, the Firefox screen that was there showed up and it was shaking very heavily.

Please help.
Thanks in advance.
Ilia

[Steve R Jones]

Does rebooting the computer make the shaking stop?

Is the screensaver you are using NEW and or have you tried a different one??

[jdc2000]

Windows 10 - Check to make sure that you did not get a helpful "update" from Microsoft that was for your video adapter or monitor drivers. A System Restore to a time when the monitor issue was not present might be worth trying. Note that Windows 10 does not have System Restore enabled by default. If your Windows 10 system does not have it enabled, I recommend that you enable it, though that won't help with this issue if it wasn't enabled.

If you have another computer that you can connect the monitor to, or another monitor that you can connect to the present computer, and a different monitor video cable, testing those possibilities might be useful in determining if it is the monitor, the video adapter, or the monitor video cable. If the monitor and cable work on another computer, that eliminates those items as the cause. If the computer works OK using another monitor or video cable, that would also pinpoint the issue.

[Shaggy Hiker]

I would certainly want to try the monitor on a different computer. As long as you have some other computer you can try it on, even an old one, that would likely narrow it down more than anything else.

Back in the days of CRT monitors, my first thought would be that you were getting some EF interference, but I've never known that to happen on any flat screen.

[IliaPreston]

I replaced the monitor, and the problem is fixed.
It is now clear that the problem was with the monitor, and not with the video card or the computer.

Thanks everybody for the help and advice.
Ilia

[Lord Orwell]

well, i would still try the monitor on a different computer. It's *possible* that your refresh rate got screwed up somehow. That definitely sounds like an issue with vertical sync. Plus, if your new monitor uses displayport and the old one didn't, it could be the video card. Displayport syncs signals differently and depending on various factors, the timing is not necessarily coming from your card.