Screen flickering/visible wave

[A_Goat]

Recently my girlfriends monitor started flickering. Flickering as in like... a bad connection, bad LCD, etc. I couldn't get the flickering to show up on video or camera so I'll try to describe it as best I can.

The flickering is NOT off/on (screen does NOT go black and back to normal rapidly)
The flickering is more like shaded "waves" rolling through the screen up and down.
The flickering only happens when the GPU is working hard (gaming)
The flickering is NOT screen tearing




I tested multiple monitors on the computer, and they all flickered the same even though they work fine on other computers... so I was convinced it was the GPU. We went out and bought another GPU but it still flickers. I tried the two GPUs in another computer, and they do not cause the flickering.

This leads me to believe it is maybe the motherboard itself. Or maybe the power supply... although I'm not sure if that's possible. What are your thoughts?

Can dust cause this? I took a can of compressed air very briefly to the PCI slot when I installed the new GPU... there was no change. Should I open it back up and clean it better?

The specs of the computer in questions are;
i7-860
OEM Motherboard for Dell xps 8300
7850 2GB / 660ti 2GB (the two GPUs I've tried)
6GB 1333 RAM
Corsair CX600 PSU

 

[Dark Lord of Tech]

Sometimes is caused by Monitor power source failing.

What TYPE connection VGA , DVI ?

 

[A_Goat]

I don't think its the monitor power source as the monitors are only acting up on the one computer. All of them work fine on another computer I have
Connection is DVI adapter to VGA and it also flickers on HDMI to HDMI.

 

[A_Goat]

Update on this...
I've swapped RAM and the PSU with other known to be working sticks of RAM and PSU.
No change...

Too bad I don't have a 1156 socket motherboard laying around to test that too... what could this be? The only thing left would be CPU and motherboard of things I haven't swapped out or replaced. Is it possible its not even hardware related?

If it IS possible it could be the motherboard, I have no problems buying a motherboard replacement... they are going for less than 70 bucks on ebay. I just don't know what could be causing this

 

[Solandri]

Have you tried a different monitor cable? This type of interference on analog cables was typically caused by RF interference being picked up by the cable. The chokes (the fat cylinders at both ends of the cable) are magnets designed to suppress this RF interference.

It's really odd that you're getting this with an HDMI to HDMI connection. That should be impossible since it's digital to digital. If you're really getting this with a pure digital connection and it's happening on multiple monitors, then it's probably a problem with the AC power coming from your wall outlet that's powering the monitors. Can you try it plugged into a different outlet, or even carry everything over to a friend's house and try it there?

The only way I could see it being caused by the motherboard is if the MB somehow wasn't grounded or was losing ground. That would cause a ground loop between it and other (grounded) devices. Basically, the motherboard is grounding itself through the GPU -> video cable -> monitor -> monitor plug -> wall outlet. But the typical PSU to motherboard connections have like a half dozen ground cables precisely to avoid this sort of problem.

Oooh, wait. Are both computer and monitor plugged into a wall outlet? If they are, can you try plugging a power strip into one of the outlets and plugging both computer and monitor into the power strip? Maybe the ground terminal on one of your wall outlets came off or isn't contacting the plug. So the computer's outlet has no ground, while the monitor's outlet is grounded, and this is forming a ground loop. Edit: Change both your computer and monitor power cables while you're at it - one of them could be faulty too.

 

[Dark Lord of Tech]

Yes motherboard is still a possibility.

 

[A_Goat]

Have you tried a different monitor cable? This type of interference on analog cables was typically caused by RF interference being picked up by the cable. The chokes (the fat cylinders at both ends of the cable) are magnets designed to suppress this RF interference.

It's really odd that you're getting this with an HDMI to HDMI connection. That should be impossible since it's digital to digital. If you're really getting this with a pure digital connection and it's happening on multiple monitors, then it's probably a problem with the AC power coming from your wall outlet that's powering the monitors. Can you try it plugged into a different outlet, or even carry everything over to a friend's house and try it there?

The only way I could see it being caused by the motherboard is if the MB somehow wasn't grounded or was losing ground. That would cause a ground loop between it and other (grounded) devices. Basically, the motherboard is grounding itself through the GPU -> video cable -> monitor -> monitor plug -> wall outlet. But the typical PSU to motherboard connections have like a half dozen ground cables precisely to avoid this sort of problem.

Oooh, wait. Are both computer and monitor plugged into a wall outlet? If they are, can you try plugging a power strip into one of the outlets and plugging both computer and monitor into the power strip? Maybe the ground terminal on one of your wall outlets came off or isn't contacting the plug. So the computer's outlet has no ground, while the monitor's outlet is grounded, and this is forming a ground loop. Edit: Change both your computer and monitor power cables while you're at it - one of them could be faulty too.

I have two computers in my living room that are plugged into different wall outlets but are on the same circuit. Monitors, cable/connection boxes, and desk items like a lamp and candle burner are the only other things on that circuit.

Little update and clarification on what I've tried so far;
All three of the monitors work completely fine on the other computer on that circuit, even if I swap around cables and use different adapters etc. I've also tried swapping out the different cables (PSU power cable, VGA cable, HDMI) for use with the problem computer but there is no change. I have also tried running an extension cord from a different circuit into the living room and trying to run everything for the problem computer off of a power strip... no change. I also did things like just running the monitor off of the extension cord, and/or only running the tower off of the extension cord... no change.

I took my computer up to micro-center ready to buy a new mobo, but the damn thing worked completely fine there (using their cables and monitor). I'm taking it over to my friends house later with my cables and monitor to see if it works there.... I just don't understand if its the cables/power why they work fine on my other computer...

Thank you for your detailed response Solandri.

 

[A_Goat]

Update on this....
I double checked the HDMI to HDMI connection and the flickering still occurred.
For some reason... DVI-D works without issues.

WTF lol?

 

[Dark Lord of Tech]

That is strange.

 

[korposarnold]

I know this post is dead, but for those happening to pass by in search of a solution, there is an easy fix to this http://i.hizliresim.com/8lYz5n.jpg

 

[Solandri]

Taping up the ground prong on your power cord eliminates the ground loop I described (if all affected devices are taped up). It's not recommended though because the purpose of the ground prong is to save your life in the event of a short circuit. If there's a short, excess electricity flows through the ground prong causing the circuit breaker to trip. If there is no ground prong, the excess electricity flows through you next time you touch the computer, possibly killing you.

The better fix is to plug all your devices into the same outlet (via a power strip like I suggested) to give them a shared ground. Or to find the equipment which is leaking current and fix or replace it. There are also ground loop isolaters you can buy, but they tend to be a bit expensive (mostly used for audio equipment, where ground loop shows up as a constant hum).