# Screen flickering with a monitor and a projector plugged in.



## mrpeter (Apr 18, 2014)

Hi,
I have got a really complicated problem with screen flickering or vibrating, I do not know how to call it I am not native speaker.
I'll explain you step by step the details. 
So I have a Samsung SyncMaster LCD monitor with a resolution of 1680x1050, an Nvidia GeForce GTS 450 grapichs card, and an Acer projector, 2 regular, thin and a thicker (theoretically more protected from interference than the other 2) VGA cables, 2 DVI adapters and a HDMI cable.
The monitor is attached to the computer with a thin cable, and it works fine, but when I plug the projector in with the other thin cable the monitor starts to flicker, horizontal lines run up on the screen, they can be hardly seen, but they are there. The picture that the projector gives is alright as I see. 
When I plug the projector in with the thick cable, the monitor flickers and the projected image too, but this time the flickering stronger a liitle bit. When I pull out the cable of the projector the flickering stops on the monitor, but when I pull out the cable of the monitor the flickering still there on the projected image. Also I tried the projector with a HDMI cable, then only the monitor flickers.
All cabels and the projector works fine with a laptop.
Please help me!


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## JimE (Apr 16, 2009)

Try lowering the resolution of one or both screens. Could be the video card is having trouble driving both screens at the current resolution.


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## Tyree (May 10, 2009)

Brand & Model of the PSU?


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## mrpeter (Apr 18, 2014)

I've tried almost every resolutions, but nothing changed.

Power supply unit is the following: LcPower LC6550 550W


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## emosun (Oct 4, 2006)

I've had similar problems like this before and found that the actual power plugs for monitors will effect the monitor itself.

It's the same effect when you try running power tools and monitors from the same plug , the monitor needs the power from the wall to be stable , try plugging the monitor and projector into an outlet that is on another breaker in the house and doesn't have anything else drawing from it.


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## Tyree (May 10, 2009)

Unstable power for the monitor is certainly a suspect as well as the low quality LCPower PSU.


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## mrpeter (Apr 18, 2014)

I've tried to plug them in the wall but the flickering still persist, maybe only decreased.

Do you think I'd need a stronger PSU?


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## Tyree (May 10, 2009)

Your PSU is certainly lower quality and replacing it with a good quality unit is a win/win deal but I can't say for certain it is the problem. Do you have or can you borrow a good quality 450W minimum PSU to try?


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## mrpeter (Apr 18, 2014)

Unfortunately I can't borrow one.


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